[clang] [llvm] [RISCV][VLS] Support RISCV VLS calling convention (PR #100346)

Brandon Wu via llvm-commits llvm-commits at lists.llvm.org
Sun Jan 5 23:16:34 PST 2025


https://github.com/4vtomat updated https://github.com/llvm/llvm-project/pull/100346

>From 8a4257e75fb37a31c77c33bed35b8a7023065e3e Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Sun, 21 Jul 2024 09:49:11 -0700
Subject: [PATCH 1/6] [RISCV][VLS] Support RISCV VLS calling convention

This patch adds a function attribute `riscv_vls_cc` for RISCV VLS calling
convention which takes 0 or 1 argument, the argument is the `ABI_VLEN`
which is the `VLEN` for passing the fixed-vector arguments, it wraps the
argument as a scalable vector(VLA) using the `ABI_VLEN` and uses the
corresponding mechanism to handle it. The range of `ABI_VLEN` is [32, 65536],
if not specified, the default value is 128.

Here is an example of VLS argument passing:
Non-VLS call:
```
  void original_call(__attribute__((vector_size(16))) int arg) {}
=>
  define void @original_call(i128 noundef %arg) {
  entry:
    ...
    ret void
  }
```
VLS call:
```
  void __attribute__((riscv_vls_cc(256))) vls_call(__attribute__((vector_size(16))) int arg) {}
=>
  define riscv_vls_cc void @vls_call(<vscale x 1 x i32> %arg) {
  entry:
    ...
    ret void
  }
}
```

The first Non-VLS call passes generic vector argument of 16 bytes by
flattened integer.
On the contrary, the VLS call uses `ABI_VLEN=256` which wraps the
vector to <vscale x 1 x i32> where the number of scalable vector elements
is calaulated by: `ORIG_ELTS * RVV_BITS_PER_BLOCK / ABI_VLEN`.
Note: ORIG_ELTS = Vector Size / Type Size = 128 / 32 = 4.
---
 clang/include/clang-c/Index.h                 |  1 +
 clang/include/clang/AST/Type.h                | 26 +++++-
 clang/include/clang/AST/TypeProperties.td     |  7 +-
 clang/include/clang/Basic/Attr.td             |  8 ++
 clang/include/clang/Basic/AttrDocs.td         | 11 +++
 clang/include/clang/Basic/CodeGenOptions.def  |  3 +
 clang/include/clang/Basic/Specifiers.h        |  1 +
 clang/include/clang/CodeGen/CGFunctionInfo.h  |  9 +-
 clang/include/clang/Driver/Options.td         |  5 +-
 clang/lib/AST/ASTContext.cpp                  |  2 +
 clang/lib/AST/ItaniumMangle.cpp               |  1 +
 clang/lib/AST/Type.cpp                        |  2 +
 clang/lib/AST/TypePrinter.cpp                 |  6 ++
 clang/lib/Basic/Targets/RISCV.cpp             |  1 +
 clang/lib/CodeGen/CGCall.cpp                  |  5 +
 clang/lib/CodeGen/CGDebugInfo.cpp             |  2 +
 clang/lib/CodeGen/CodeGenModule.cpp           |  3 +-
 clang/lib/CodeGen/TargetInfo.h                |  2 +-
 clang/lib/CodeGen/Targets/RISCV.cpp           | 91 +++++++++++++------
 clang/lib/Driver/ToolChains/Arch/RISCV.cpp    |  4 +
 clang/lib/Driver/ToolChains/Clang.cpp         | 15 +++
 clang/lib/Sema/SemaDeclAttr.cpp               | 40 +++++++-
 clang/lib/Sema/SemaType.cpp                   | 26 +++++-
 .../RISCV/riscv-vector-callingconv-llvm-ir.c  | 40 ++++++++
 .../riscv-vector-callingconv-llvm-ir.cpp      | 22 +++++
 .../CodeGen/RISCV/riscv-vector-callingconv.c  | 18 ++++
 .../RISCV/riscv-vector-callingconv.cpp        | 18 ++++
 clang/tools/libclang/CXType.cpp               |  1 +
 llvm/include/llvm/AsmParser/LLToken.h         |  1 +
 llvm/include/llvm/BinaryFormat/Dwarf.def      |  1 +
 llvm/include/llvm/IR/CallingConv.h            |  3 +
 llvm/lib/AsmParser/LLLexer.cpp                |  1 +
 llvm/lib/AsmParser/LLParser.cpp               |  4 +
 llvm/lib/IR/AsmWriter.cpp                     |  3 +
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp   |  1 +
 llvm/test/Assembler/riscv_vls_cc.ll           | 12 +++
 llvm/test/Bitcode/compatibility.ll            |  4 +
 37 files changed, 358 insertions(+), 42 deletions(-)
 create mode 100644 llvm/test/Assembler/riscv_vls_cc.ll

diff --git a/clang/include/clang-c/Index.h b/clang/include/clang-c/Index.h
index 0c5ac80772e2b9..696f9ca59546c6 100644
--- a/clang/include/clang-c/Index.h
+++ b/clang/include/clang-c/Index.h
@@ -3013,6 +3013,7 @@ enum CXCallingConv {
   CXCallingConv_M68kRTD = 19,
   CXCallingConv_PreserveNone = 20,
   CXCallingConv_RISCVVectorCall = 21,
+  CXCallingConv_RISCVVLSCall = 22,
 
   CXCallingConv_Invalid = 100,
   CXCallingConv_Unexposed = 200
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index 1bcc7ee0b70dee..5b30a31d1787db 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -1953,7 +1953,7 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     /// Extra information which affects how the function is called, like
     /// regparm and the calling convention.
     LLVM_PREFERRED_TYPE(CallingConv)
-    unsigned ExtInfo : 13;
+    unsigned ExtInfo : 18;
 
     /// The ref-qualifier associated with a \c FunctionProtoType.
     ///
@@ -4440,6 +4440,8 @@ class FunctionType : public Type {
 
     // |  CC  |noreturn|produces|nocallersavedregs|regparm|nocfcheck|cmsenscall|
     // |0 .. 4|   5    |    6   |       7         |8 .. 10|    11   |    12    |
+    // |RISCV-ABI-VLEN|
+    // |13    ..    17|
     //
     // regparm is either 0 (no regparm attribute) or the regparm value+1.
     enum { CallConvMask = 0x1F };
@@ -4452,23 +4454,25 @@ class FunctionType : public Type {
     };
     enum { NoCfCheckMask = 0x800 };
     enum { CmseNSCallMask = 0x1000 };
-    uint16_t Bits = CC_C;
+    enum { Log2RISCVABIVLenMask = 0x3E000, Log2RISCVABIVLenOffset = 13 };
+    uint32_t Bits = CC_C;
 
-    ExtInfo(unsigned Bits) : Bits(static_cast<uint16_t>(Bits)) {}
+    ExtInfo(unsigned Bits) : Bits(static_cast<uint32_t>(Bits)) {}
 
   public:
     // Constructor with no defaults. Use this when you know that you
     // have all the elements (when reading an AST file for example).
     ExtInfo(bool noReturn, bool hasRegParm, unsigned regParm, CallingConv cc,
             bool producesResult, bool noCallerSavedRegs, bool NoCfCheck,
-            bool cmseNSCall) {
+            bool cmseNSCall, unsigned Log2RISCVABIVLen) {
       assert((!hasRegParm || regParm < 7) && "Invalid regparm value");
       Bits = ((unsigned)cc) | (noReturn ? NoReturnMask : 0) |
              (producesResult ? ProducesResultMask : 0) |
              (noCallerSavedRegs ? NoCallerSavedRegsMask : 0) |
              (hasRegParm ? ((regParm + 1) << RegParmOffset) : 0) |
              (NoCfCheck ? NoCfCheckMask : 0) |
-             (cmseNSCall ? CmseNSCallMask : 0);
+             (cmseNSCall ? CmseNSCallMask : 0) |
+             (Log2RISCVABIVLen << Log2RISCVABIVLenOffset);
     }
 
     // Constructor with all defaults. Use when for example creating a
@@ -4495,6 +4499,10 @@ class FunctionType : public Type {
 
     CallingConv getCC() const { return CallingConv(Bits & CallConvMask); }
 
+    unsigned getLog2RISCVABIVLen() const {
+      return (Bits & Log2RISCVABIVLenMask) >> Log2RISCVABIVLenOffset;
+    }
+
     bool operator==(ExtInfo Other) const {
       return Bits == Other.Bits;
     }
@@ -4550,6 +4558,11 @@ class FunctionType : public Type {
       return ExtInfo((Bits & ~CallConvMask) | (unsigned) cc);
     }
 
+    ExtInfo withLog2RISCVABIVLen(unsigned Log2RISCVABIVLen) const {
+      return ExtInfo((Bits & ~Log2RISCVABIVLenMask) |
+                     (Log2RISCVABIVLen << Log2RISCVABIVLenOffset));
+    }
+
     void Profile(llvm::FoldingSetNodeID &ID) const {
       ID.AddInteger(Bits);
     }
@@ -4654,6 +4667,9 @@ class FunctionType : public Type {
 
   bool getCmseNSCallAttr() const { return getExtInfo().getCmseNSCall(); }
   CallingConv getCallConv() const { return getExtInfo().getCC(); }
+  unsigned getLog2RISCVABIVLen() const {
+    return getExtInfo().getLog2RISCVABIVLen();
+  }
   ExtInfo getExtInfo() const { return ExtInfo(FunctionTypeBits.ExtInfo); }
 
   static_assert((~Qualifiers::FastMask & Qualifiers::CVRMask) == 0,
diff --git a/clang/include/clang/AST/TypeProperties.td b/clang/include/clang/AST/TypeProperties.td
index 42f62695963a2d..22eba9c0ca8c79 100644
--- a/clang/include/clang/AST/TypeProperties.td
+++ b/clang/include/clang/AST/TypeProperties.td
@@ -313,6 +313,9 @@ let Class = FunctionType in {
   def : Property<"cmseNSCall", Bool> {
     let Read = [{ node->getExtInfo().getCmseNSCall() }];
   }
+  def : Property<"Log2RISCVABIVLen", UInt32> {
+    let Read = [{ node->getExtInfo().getLog2RISCVABIVLen() }];
+  }
 }
 
 let Class = FunctionNoProtoType in {
@@ -320,7 +323,7 @@ let Class = FunctionNoProtoType in {
     auto extInfo = FunctionType::ExtInfo(noReturn, hasRegParm, regParm,
                                          callingConvention, producesResult,
                                          noCallerSavedRegs, noCfCheck,
-                                         cmseNSCall);
+                                         cmseNSCall, Log2RISCVABIVLen);
     return ctx.getFunctionNoProtoType(returnType, extInfo);
   }]>;
 }
@@ -363,7 +366,7 @@ let Class = FunctionProtoType in {
     auto extInfo = FunctionType::ExtInfo(noReturn, hasRegParm, regParm,
                                          callingConvention, producesResult,
                                          noCallerSavedRegs, noCfCheck,
-                                         cmseNSCall);
+                                         cmseNSCall, Log2RISCVABIVLen);
     FunctionProtoType::ExtProtoInfo epi;
     epi.ExtInfo = extInfo;
     epi.Variadic = variadic;
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 156fbd1c4442eb..47c03a7eca20ab 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -3204,6 +3204,14 @@ def RISCVVectorCC: DeclOrTypeAttr, TargetSpecificAttr<TargetRISCV> {
  let Documentation = [RISCVVectorCCDocs];
 }
 
+def RISCVVLSCC: DeclOrTypeAttr, TargetSpecificAttr<TargetRISCV> {
+ let Spellings = [CXX11<"riscv", "vls_cc">,
+                  C23<"riscv", "vls_cc">,
+                  Clang<"riscv_vls_cc">];
+ let Args = [UnsignedArgument<"VectorWidth", /*opt*/1>];
+ let Documentation = [RISCVVLSCCDocs];
+}
+
 def Target : InheritableAttr {
   let Spellings = [GCC<"target">];
   let Args = [StringArgument<"featuresStr">];
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index b497cce37625c9..c2ab6cc115d6cd 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -5645,6 +5645,17 @@ them if they use them.
  }];
 }
 
+def RISCVVLSCCDocs : Documentation {
+ let Category = DocCatCallingConvs;
+ let Heading = "riscv::vls_cc, riscv_vls_cc, clang::riscv_vls_cc";
+ let Content = [{
+The ``riscv_vls_cc`` attribute can be applied to a function. Functions
+declared with this attribute will utilize the standard fixed-length vector
+calling convention variant instead of the default calling convention defined by
+the ABI. This variant aims to pass fixed-length vectors via vector registers,
+if possible, rather than through general-purpose registers.}];
+}
+
 def PreferredNameDocs : Documentation {
   let Category = DocCatDecl;
   let Content = [{
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index e45370bde74a5d..894aaff054b631 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -464,6 +464,9 @@ ENUM_CODEGENOPT(ZeroCallUsedRegs, llvm::ZeroCallUsedRegs::ZeroCallUsedRegsKind,
 /// non-deleting destructors. (No effect on Microsoft ABI.)
 CODEGENOPT(CtorDtorReturnThis, 1, 0)
 
+/// Specify the VLEN for VLS calling convention.
+CODEGENOPT(RISCVABIVLen, 17, 0)
+
 /// FIXME: Make DebugOptions its own top-level .def file.
 #include "DebugOptions.def"
 
diff --git a/clang/include/clang/Basic/Specifiers.h b/clang/include/clang/Basic/Specifiers.h
index 9c089908fdc130..d2df5a24da143e 100644
--- a/clang/include/clang/Basic/Specifiers.h
+++ b/clang/include/clang/Basic/Specifiers.h
@@ -300,6 +300,7 @@ namespace clang {
     CC_M68kRTD,           // __attribute__((m68k_rtd))
     CC_PreserveNone,      // __attribute__((preserve_none))
     CC_RISCVVectorCall,   // __attribute__((riscv_vector_cc))
+    CC_RISCVVLSCall,      // __attribute__((riscv_vls_cc))
   };
 
   /// Checks whether the given calling convention supports variadic
diff --git a/clang/include/clang/CodeGen/CGFunctionInfo.h b/clang/include/clang/CodeGen/CGFunctionInfo.h
index 9d785d878b61dc..44ae2755a2ab04 100644
--- a/clang/include/clang/CodeGen/CGFunctionInfo.h
+++ b/clang/include/clang/CodeGen/CGFunctionInfo.h
@@ -625,6 +625,9 @@ class CGFunctionInfo final
   /// Log 2 of the maximum vector width.
   unsigned MaxVectorWidth : 4;
 
+  /// Log2 of ABI_VLEN used in RISCV VLS calling convention.
+  unsigned Log2RISCVABIVLen : 5;
+
   RequiredArgs Required;
 
   /// The struct representing all arguments passed in memory.  Only used when
@@ -735,11 +738,13 @@ class CGFunctionInfo final
   bool getHasRegParm() const { return HasRegParm; }
   unsigned getRegParm() const { return RegParm; }
 
+  unsigned getLog2RISCVABIVLen() const { return Log2RISCVABIVLen; }
+
   FunctionType::ExtInfo getExtInfo() const {
     return FunctionType::ExtInfo(isNoReturn(), getHasRegParm(), getRegParm(),
                                  getASTCallingConvention(), isReturnsRetained(),
                                  isNoCallerSavedRegs(), isNoCfCheck(),
-                                 isCmseNSCall());
+                                 isCmseNSCall(), getLog2RISCVABIVLen());
   }
 
   CanQualType getReturnType() const { return getArgsBuffer()[0].type; }
@@ -793,6 +798,7 @@ class CGFunctionInfo final
     ID.AddInteger(RegParm);
     ID.AddBoolean(NoCfCheck);
     ID.AddBoolean(CmseNSCall);
+    ID.AddInteger(Log2RISCVABIVLen);
     ID.AddInteger(Required.getOpaqueData());
     ID.AddBoolean(HasExtParameterInfos);
     if (HasExtParameterInfos) {
@@ -820,6 +826,7 @@ class CGFunctionInfo final
     ID.AddInteger(info.getRegParm());
     ID.AddBoolean(info.getNoCfCheck());
     ID.AddBoolean(info.getCmseNSCall());
+    ID.AddInteger(info.getLog2RISCVABIVLen());
     ID.AddInteger(required.getOpaqueData());
     ID.AddBoolean(!paramInfos.empty());
     if (!paramInfos.empty()) {
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 805b79491e6ea4..eeac988ba5ead9 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4950,7 +4950,10 @@ def mrvv_vector_bits_EQ : Joined<["-"], "mrvv-vector-bits=">, Group<m_Group>,
       !eq(GlobalDocumentation.Program, "Flang") : "",
       true: " The value will be reflected in __riscv_v_fixed_vlen preprocessor define"),
     " (RISC-V only)")>;
-
+def mriscv_abi_vlen_EQ : Joined<["-"], "mriscv-abi-vlen=">, Group<m_Group>,
+  Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Specify the VLEN for VLS calling convention.">,
+  MarshallingInfoInt<CodeGenOpts<"RISCVABIVLen">>;
 def munaligned_access : Flag<["-"], "munaligned-access">, Group<m_Group>,
   HelpText<"Allow memory accesses to be unaligned (AArch32/MIPSr6 only)">;
 def mno_unaligned_access : Flag<["-"], "mno-unaligned-access">, Group<m_Group>,
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 11e79d296cbec3..0b3ed5d9b663e3 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -11046,6 +11046,8 @@ QualType ASTContext::mergeFunctionTypes(QualType lhs, QualType rhs,
     return {};
   if (lbaseInfo.getNoCfCheck() != rbaseInfo.getNoCfCheck())
     return {};
+  if (lbaseInfo.getLog2RISCVABIVLen() != rbaseInfo.getLog2RISCVABIVLen())
+    return {};
 
   // When merging declarations, it's common for supplemental information like
   // attributes to only be present in one of the declarations, and we generally
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 14bc260d0245fb..730c2fda1aae4c 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -3490,6 +3490,7 @@ StringRef CXXNameMangler::getCallingConvQualifierName(CallingConv CC) {
   case CC_M68kRTD:
   case CC_PreserveNone:
   case CC_RISCVVectorCall:
+  case CC_RISCVVLSCall:
     // FIXME: we should be mangling all of the above.
     return "";
 
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 6bf2908e667c07..6664f7d5ae9507 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -3529,6 +3529,7 @@ StringRef FunctionType::getNameForCallConv(CallingConv CC) {
   case CC_PreserveNone: return "preserve_none";
     // clang-format off
   case CC_RISCVVectorCall: return "riscv_vector_cc";
+  case CC_RISCVVLSCall: return "riscv_vls_cc";
     // clang-format on
   }
 
@@ -4196,6 +4197,7 @@ bool AttributedType::isCallingConv() const {
   case attr::M68kRTD:
   case attr::PreserveNone:
   case attr::RISCVVectorCC:
+  case attr::RISCVVLSCC:
     return true;
   }
   llvm_unreachable("invalid attr kind");
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 6d8db5cf4ffd22..1e1794fc3ad882 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -1135,6 +1135,9 @@ void TypePrinter::printFunctionAfter(const FunctionType::ExtInfo &Info,
     case CC_RISCVVectorCall:
       OS << "__attribute__((riscv_vector_cc))";
       break;
+    case CC_RISCVVLSCall:
+      OS << "__attribute__((riscv_vls_cc))";
+      break;
     }
   }
 
@@ -2053,6 +2056,9 @@ void TypePrinter::printAttributedAfter(const AttributedType *T,
   case attr::RISCVVectorCC:
     OS << "riscv_vector_cc";
     break;
+  case attr::RISCVVLSCC:
+    OS << "riscv_vls_cc";
+    break;
   case attr::NoDeref:
     OS << "noderef";
     break;
diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index eaaba7642bd7b2..c9c32330d34af9 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -483,6 +483,7 @@ RISCVTargetInfo::checkCallingConvention(CallingConv CC) const {
     return CCCR_Warning;
   case CC_C:
   case CC_RISCVVectorCall:
+  case CC_RISCVVLSCall:
     return CCCR_OK;
   }
 }
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 8f4f5d3ed81601..816c5ebc18623c 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -77,6 +77,7 @@ unsigned CodeGenTypes::ClangCallConvToLLVMCallConv(CallingConv CC) {
   case CC_PreserveNone: return llvm::CallingConv::PreserveNone;
     // clang-format off
   case CC_RISCVVectorCall: return llvm::CallingConv::RISCV_VectorCall;
+  case CC_RISCVVLSCall: return llvm::CallingConv::RISCV_VLSCall;
     // clang-format on
   }
 }
@@ -267,6 +268,9 @@ static CallingConv getCallingConventionForDecl(const ObjCMethodDecl *D,
   if (D->hasAttr<RISCVVectorCCAttr>())
     return CC_RISCVVectorCall;
 
+  if (D->hasAttr<RISCVVLSCCAttr>())
+    return CC_RISCVVLSCall;
+
   return CC_C;
 }
 
@@ -862,6 +866,7 @@ CGFunctionInfo *CGFunctionInfo::create(unsigned llvmCC, bool instanceMethod,
   FI->HasExtParameterInfos = !paramInfos.empty();
   FI->getArgsBuffer()[0].type = resultType;
   FI->MaxVectorWidth = 0;
+  FI->Log2RISCVABIVLen = info.getLog2RISCVABIVLen();
   for (unsigned i = 0, e = argTypes.size(); i != e; ++i)
     FI->getArgsBuffer()[i + 1].type = argTypes[i];
   for (unsigned i = 0, e = paramInfos.size(); i != e; ++i)
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index ad64abe7cd40a3..38149305eb2442 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1595,6 +1595,8 @@ static unsigned getDwarfCC(CallingConv CC) {
     return llvm::dwarf::DW_CC_LLVM_PreserveNone;
   case CC_RISCVVectorCall:
     return llvm::dwarf::DW_CC_LLVM_RISCVVectorCall;
+  case CC_RISCVVLSCall:
+    return llvm::dwarf::DW_CC_LLVM_RISCVVectorCall;
   }
   return 0;
 }
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index ba376f9ecfacde..dcb43b3da26af8 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -234,7 +234,8 @@ createTargetCodeGenInfo(CodeGenModule &CGM) {
     else if (ABIStr.ends_with("d"))
       ABIFLen = 64;
     bool EABI = ABIStr.ends_with("e");
-    return createRISCVTargetCodeGenInfo(CGM, XLen, ABIFLen, EABI);
+    return createRISCVTargetCodeGenInfo(CGM, XLen, ABIFLen,
+                                        CodeGenOpts.RISCVABIVLen, EABI);
   }
 
   case llvm::Triple::systemz: {
diff --git a/clang/lib/CodeGen/TargetInfo.h b/clang/lib/CodeGen/TargetInfo.h
index 373f8b8a80fdb1..e94d04f1159404 100644
--- a/clang/lib/CodeGen/TargetInfo.h
+++ b/clang/lib/CodeGen/TargetInfo.h
@@ -533,7 +533,7 @@ createPPC64_SVR4_TargetCodeGenInfo(CodeGenModule &CGM, PPC64_SVR4_ABIKind Kind,
 
 std::unique_ptr<TargetCodeGenInfo>
 createRISCVTargetCodeGenInfo(CodeGenModule &CGM, unsigned XLen, unsigned FLen,
-                             bool EABI);
+                             unsigned ABIVLen, bool EABI);
 
 std::unique_ptr<TargetCodeGenInfo>
 createCommonSPIRTargetCodeGenInfo(CodeGenModule &CGM);
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index b04e436c665f52..35763b824a7168 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -8,6 +8,7 @@
 
 #include "ABIInfoImpl.h"
 #include "TargetInfo.h"
+#include "llvm/TargetParser/RISCVTargetParser.h"
 
 using namespace clang;
 using namespace clang::CodeGen;
@@ -25,6 +26,7 @@ class RISCVABIInfo : public DefaultABIInfo {
   // ISA might have a wider FLen than the selected ABI (e.g. an RV32IF target
   // with soft float ABI has FLen==0).
   unsigned FLen;
+  unsigned ABIVLen;
   const int NumArgGPRs;
   const int NumArgFPRs;
   const bool EABI;
@@ -36,17 +38,17 @@ class RISCVABIInfo : public DefaultABIInfo {
 
 public:
   RISCVABIInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen, unsigned FLen,
-               bool EABI)
-      : DefaultABIInfo(CGT), XLen(XLen), FLen(FLen), NumArgGPRs(EABI ? 6 : 8),
-        NumArgFPRs(FLen != 0 ? 8 : 0), EABI(EABI) {}
+               unsigned ABIVLen, bool EABI)
+      : DefaultABIInfo(CGT), XLen(XLen), FLen(FLen), ABIVLen(ABIVLen),
+        NumArgGPRs(EABI ? 6 : 8), NumArgFPRs(FLen != 0 ? 8 : 0), EABI(EABI) {}
 
   // DefaultABIInfo's classifyReturnType and classifyArgumentType are
   // non-virtual, but computeInfo is virtual, so we overload it.
   void computeInfo(CGFunctionInfo &FI) const override;
 
   ABIArgInfo classifyArgumentType(QualType Ty, bool IsFixed, int &ArgGPRsLeft,
-                                  int &ArgFPRsLeft) const;
-  ABIArgInfo classifyReturnType(QualType RetTy) const;
+                                  int &ArgFPRsLeft, unsigned ArgABIVLen) const;
+  ABIArgInfo classifyReturnType(QualType RetTy, unsigned ArgABIVLen) const;
 
   RValue EmitVAArg(CodeGenFunction &CGF, Address VAListAddr, QualType Ty,
                    AggValueSlot Slot) const override;
@@ -62,7 +64,7 @@ class RISCVABIInfo : public DefaultABIInfo {
                                                llvm::Type *Field2Ty,
                                                CharUnits Field2Off) const;
 
-  ABIArgInfo coerceVLSVector(QualType Ty) const;
+  ABIArgInfo coerceVLSVector(QualType Ty, unsigned ArgABIVLen = 0) const;
 
   using ABIInfo::appendAttributeMangling;
   void appendAttributeMangling(TargetClonesAttr *Attr, unsigned Index,
@@ -111,9 +113,13 @@ void RISCVABIInfo::appendAttributeMangling(StringRef AttrStr,
 }
 
 void RISCVABIInfo::computeInfo(CGFunctionInfo &FI) const {
+  unsigned ArgABIVLen = 1 << FI.getExtInfo().getLog2RISCVABIVLen();
+  if (ArgABIVLen == 1)
+    ArgABIVLen = ABIVLen;
+
   QualType RetTy = FI.getReturnType();
   if (!getCXXABI().classifyReturnType(FI))
-    FI.getReturnInfo() = classifyReturnType(RetTy);
+    FI.getReturnInfo() = classifyReturnType(RetTy, ArgABIVLen);
 
   // IsRetIndirect is true if classifyArgumentType indicated the value should
   // be passed indirect, or if the type size is a scalar greater than 2*XLen
@@ -139,8 +145,8 @@ void RISCVABIInfo::computeInfo(CGFunctionInfo &FI) const {
   int ArgNum = 0;
   for (auto &ArgInfo : FI.arguments()) {
     bool IsFixed = ArgNum < NumFixedArgs;
-    ArgInfo.info =
-        classifyArgumentType(ArgInfo.type, IsFixed, ArgGPRsLeft, ArgFPRsLeft);
+    ArgInfo.info = classifyArgumentType(ArgInfo.type, IsFixed, ArgGPRsLeft,
+                                        ArgFPRsLeft, ArgABIVLen);
     ArgNum++;
   }
 }
@@ -361,7 +367,8 @@ ABIArgInfo RISCVABIInfo::coerceAndExpandFPCCEligibleStruct(
 
 // Fixed-length RVV vectors are represented as scalable vectors in function
 // args/return and must be coerced from fixed vectors.
-ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty) const {
+ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
+                                         unsigned ArgABIVLen) const {
   assert(Ty->isVectorType() && "expected vector type!");
 
   const auto *VT = Ty->castAs<VectorType>();
@@ -385,23 +392,48 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty) const {
     NumElts *= 8;
     break;
   default:
-    assert(VT->getVectorKind() == VectorKind::RVVFixedLengthData &&
+    assert((VT->getVectorKind() == VectorKind::Generic ||
+            VT->getVectorKind() == VectorKind::RVVFixedLengthData) &&
            "Unexpected vector kind");
     EltType = CGT.ConvertType(VT->getElementType());
   }
 
-  // The MinNumElts is simplified from equation:
-  // NumElts / VScale =
-  //  (EltSize * NumElts / (VScale * RVVBitsPerBlock))
-  //    * (RVVBitsPerBlock / EltSize)
-  llvm::ScalableVectorType *ResType =
-      llvm::ScalableVectorType::get(EltType, NumElts / VScale->first);
+  llvm::ScalableVectorType *ResType;
+
+  if (ArgABIVLen == 0) {
+    // The MinNumElts is simplified from equation:
+    // NumElts / VScale =
+    //  (EltSize * NumElts / (VScale * RVVBitsPerBlock))
+    //    * (RVVBitsPerBlock / EltSize)
+    ResType = llvm::ScalableVectorType::get(EltType, NumElts / VScale->first);
+  } else {
+    // If the corresponding extension is not supported, just make it an i32
+    // vector.
+    const TargetInfo &TI = getContext().getTargetInfo();
+    if ((EltType->isHalfTy() && !TI.hasFeature("zvfhmin")) ||
+        (EltType->isBFloatTy() && !TI.hasFeature("zvfbfmin")) ||
+        (EltType->isFloatTy() && !TI.hasFeature("zve32f")) ||
+        (EltType->isDoubleTy() && !TI.hasFeature("zve64d")) ||
+        (EltType->isIntegerTy(64) && !TI.hasFeature("zve64x")) ||
+        EltType->isIntegerTy(128)) {
+      NumElts = NumElts * EltType->getScalarSizeInBits() / 32;
+      EltType = llvm::Type::getInt32Ty(getVMContext());
+    }
+
+    // Generic vector
+    // The number of element need to be at least 1.
+    ResType = llvm::ScalableVectorType::get(
+        EltType,
+        llvm::divideCeil(NumElts * llvm::RISCV::RVVBitsPerBlock, ArgABIVLen));
+  }
+
   return ABIArgInfo::getDirect(ResType);
 }
 
 ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
                                               int &ArgGPRsLeft,
-                                              int &ArgFPRsLeft) const {
+                                              int &ArgFPRsLeft,
+                                              unsigned ArgABIVLen) const {
   assert(ArgGPRsLeft <= NumArgGPRs && "Arg GPR tracking underflow");
   Ty = useFirstFieldIfTransparentUnion(Ty);
 
@@ -504,13 +536,18 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
     return Info;
   }
 
-  if (const VectorType *VT = Ty->getAs<VectorType>())
+  if (const VectorType *VT = Ty->getAs<VectorType>()) {
     if (VT->getVectorKind() == VectorKind::RVVFixedLengthData ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_1 ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_2 ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_4)
       return coerceVLSVector(Ty);
+    if (VT->getVectorKind() == VectorKind::Generic && ArgABIVLen != 0)
+      // Generic vector without riscv_vls_cc should fall through and pass by
+      // reference.
+      return coerceVLSVector(Ty, ArgABIVLen);
+  }
 
   // Aggregates which are <= 2*XLen will be passed in registers if possible,
   // so coerce to integers.
@@ -533,7 +570,8 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
   return getNaturalAlignIndirect(Ty, /*ByVal=*/false);
 }
 
-ABIArgInfo RISCVABIInfo::classifyReturnType(QualType RetTy) const {
+ABIArgInfo RISCVABIInfo::classifyReturnType(QualType RetTy,
+                                            unsigned ArgABIVLen) const {
   if (RetTy->isVoidType())
     return ABIArgInfo::getIgnore();
 
@@ -542,8 +580,8 @@ ABIArgInfo RISCVABIInfo::classifyReturnType(QualType RetTy) const {
 
   // The rules for return and argument types are the same, so defer to
   // classifyArgumentType.
-  return classifyArgumentType(RetTy, /*IsFixed=*/true, ArgGPRsLeft,
-                              ArgFPRsLeft);
+  return classifyArgumentType(RetTy, /*IsFixed=*/true, ArgGPRsLeft, ArgFPRsLeft,
+                              ArgABIVLen);
 }
 
 RValue RISCVABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
@@ -582,9 +620,9 @@ namespace {
 class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
 public:
   RISCVTargetCodeGenInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen,
-                         unsigned FLen, bool EABI)
+                         unsigned FLen, unsigned ABIVLen, bool EABI)
       : TargetCodeGenInfo(
-            std::make_unique<RISCVABIInfo>(CGT, XLen, FLen, EABI)) {
+            std::make_unique<RISCVABIInfo>(CGT, XLen, FLen, ABIVLen, EABI)) {
     SwiftInfo =
         std::make_unique<SwiftABIInfo>(CGT, /*SwiftErrorInRegister=*/false);
   }
@@ -616,7 +654,8 @@ class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
 
 std::unique_ptr<TargetCodeGenInfo>
 CodeGen::createRISCVTargetCodeGenInfo(CodeGenModule &CGM, unsigned XLen,
-                                      unsigned FLen, bool EABI) {
+                                      unsigned FLen, unsigned ABIVLen,
+                                      bool EABI) {
   return std::make_unique<RISCVTargetCodeGenInfo>(CGM.getTypes(), XLen, FLen,
-                                                  EABI);
+                                                  ABIVLen, EABI);
 }
diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
index 6935904a24edbf..18da247b3eab48 100644
--- a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -95,6 +95,10 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
       CPUFastVectorUnaligned = true;
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_mriscv_abi_vlen_EQ))
+    Features.push_back(
+        Args.MakeArgString(Twine("+abi-vlen-") + A->getValue() + "b"));
+
 // Handle features corresponding to "-ffixed-X" options
 #define RESERVE_REG(REG)                                                       \
   if (Args.hasArg(options::OPT_ffixed_##REG))                                  \
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index dca8d3fd7b3eaf..89749b64a3dfd9 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2203,6 +2203,21 @@ void Clang::AddRISCVTargetArgs(const ArgList &Args,
           << A->getSpelling() << Val;
     }
   }
+
+  if (Arg *A = Args.getLastArg(options::OPT_mriscv_abi_vlen_EQ)) {
+    StringRef ABIVLenStr = A->getValue();
+    unsigned ABIVLen;
+    const Driver &D = getToolChain().getDriver();
+    if (ABIVLenStr.getAsInteger(10, ABIVLen) || ABIVLen < 32 ||
+        ABIVLen > 65536 || !llvm::isPowerOf2_64(ABIVLen)) {
+      D.Diag(diag::err_drv_invalid_value)
+          << A->getOption().getName() << ABIVLenStr;
+      return;
+    }
+
+    CmdArgs.push_back(
+        Args.MakeArgString(Twine("-mriscv-abi-vlen=") + A->getValue()));
+  }
 }
 
 void Clang::AddSparcTargetArgs(const ArgList &Args,
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 601c6f2eef1d9c..2d1885bec36280 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -4855,6 +4855,25 @@ static void handleCallConvAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   case ParsedAttr::AT_RISCVVectorCC:
     D->addAttr(::new (S.Context) RISCVVectorCCAttr(S.Context, AL));
     return;
+  case ParsedAttr::AT_RISCVVLSCC: {
+    // If the riscv_abi_vlen doesn't have any argument, default ABI_VLEN is 128.
+    unsigned VectorLength = 128;
+    if (AL.getNumArgs() &&
+        !S.checkUInt32Argument(AL, AL.getArgAsExpr(0), VectorLength))
+      return;
+    if (VectorLength < 32 || VectorLength > 65536) {
+      S.Diag(AL.getLoc(), diag::err_argument_invalid_range)
+          << VectorLength << 32 << 65536;
+      return;
+    }
+    if (!llvm::isPowerOf2_64(VectorLength)) {
+      S.Diag(AL.getLoc(), diag::err_argument_not_power_of_2);
+      return;
+    }
+
+    D->addAttr(::new (S.Context) RISCVVLSCCAttr(S.Context, AL, VectorLength));
+    return;
+  }
   default:
     llvm_unreachable("unexpected attribute kind");
   }
@@ -4974,10 +4993,19 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
     return false;
   }
 
-  unsigned ReqArgs = Attrs.getKind() == ParsedAttr::AT_Pcs ? 1 : 0;
-  if (!Attrs.checkExactlyNumArgs(*this, ReqArgs)) {
-    Attrs.setInvalid();
-    return true;
+  if (Attrs.getKind() == ParsedAttr::AT_RISCVVLSCC) {
+    // riscv_vls_cc only accept 0 or 1 argument.
+    if (!Attrs.checkAtLeastNumArgs(*this, 0) ||
+        !Attrs.checkAtMostNumArgs(*this, 1)) {
+      Attrs.setInvalid();
+      return true;
+    }
+  } else {
+    unsigned ReqArgs = Attrs.getKind() == ParsedAttr::AT_Pcs ? 1 : 0;
+    if (!Attrs.checkExactlyNumArgs(*this, ReqArgs)) {
+      Attrs.setInvalid();
+      return true;
+    }
   }
 
   // TODO: diagnose uses of these conventions on the wrong target.
@@ -5062,6 +5090,9 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   case ParsedAttr::AT_RISCVVectorCC:
     CC = CC_RISCVVectorCall;
     break;
+  case ParsedAttr::AT_RISCVVLSCC:
+    CC = CC_RISCVVLSCall;
+    break;
   default: llvm_unreachable("unexpected attribute kind");
   }
 
@@ -6894,6 +6925,7 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_M68kRTD:
   case ParsedAttr::AT_PreserveNone:
   case ParsedAttr::AT_RISCVVectorCC:
+  case ParsedAttr::AT_RISCVVLSCC:
     handleCallConvAttr(S, D, AL);
     break;
   case ParsedAttr::AT_Suppress:
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index e526a11973975d..0b1f7f51bc05c6 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -148,7 +148,8 @@ static void diagnoseBadTypeAttribute(Sema &S, const ParsedAttr &attr,
   case ParsedAttr::AT_PreserveAll:                                             \
   case ParsedAttr::AT_M68kRTD:                                                 \
   case ParsedAttr::AT_PreserveNone:                                            \
-  case ParsedAttr::AT_RISCVVectorCC
+  case ParsedAttr::AT_RISCVVectorCC:                                           \
+  case ParsedAttr::AT_RISCVVLSCC
 
 // Function type attributes.
 #define FUNCTION_TYPE_ATTRS_CASELIST                                           \
@@ -7591,6 +7592,8 @@ static Attr *getCCTypeAttr(ASTContext &Ctx, ParsedAttr &Attr) {
     return createSimpleAttr<PreserveNoneAttr>(Ctx, Attr);
   case ParsedAttr::AT_RISCVVectorCC:
     return createSimpleAttr<RISCVVectorCCAttr>(Ctx, Attr);
+  case ParsedAttr::AT_RISCVVLSCC:
+    return ::new (Ctx) RISCVVLSCCAttr(Ctx, Attr, /*dummy*/ 0);
   }
   llvm_unreachable("unexpected attribute kind!");
 }
@@ -8031,6 +8034,27 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
   CallingConv CCOld = fn->getCallConv();
   Attr *CCAttr = getCCTypeAttr(S.Context, attr);
 
+  if (attr.getKind() == ParsedAttr::AT_RISCVVLSCC) {
+    // If the riscv_abi_vlen doesn't have any argument, default ABI_VLEN is 128.
+    unsigned ABIVLen = 128;
+    if (attr.getNumArgs() &&
+        !S.checkUInt32Argument(attr, attr.getArgAsExpr(0), ABIVLen))
+      return false;
+    if (ABIVLen < 32 || ABIVLen > 65536) {
+      S.Diag(attr.getLoc(), diag::err_argument_invalid_range)
+          << ABIVLen << 32 << 65536;
+      return false;
+    }
+    if (!llvm::isPowerOf2_64(ABIVLen)) {
+      S.Diag(attr.getLoc(), diag::err_argument_not_power_of_2);
+      return false;
+    }
+
+    auto EI = unwrapped.get()->getExtInfo().withLog2RISCVABIVLen(
+        llvm::Log2_64(ABIVLen));
+    type = unwrapped.wrap(S, S.Context.adjustFunctionType(unwrapped.get(), EI));
+  }
+
   if (CCOld != CC) {
     // Error out on when there's already an attribute on the type
     // and the CCs don't match.
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
index 072d8a863d4570..8c205459db9993 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
@@ -3,6 +3,10 @@
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
 // RUN: %clang_cc1 -std=c23 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
+// RUN: %clang_cc1 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
+// RUN: %clang_cc1 -std=c23 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
 
 #include <riscv_vector.h>
 
@@ -32,3 +36,39 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
   __riscv_vse32_v_i32m1(base, val, vl);
   return ret;
 }
+
+// CHECK-LLVM: define dso_local void @test_vls_no_cc(i128 noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local void @test_vls_no_cc(<vscale x 1 x i32> noundef %arg.coerce)
+void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 2 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 2 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen_c23(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen_c23_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc(256))) test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc(256)]] void test_vls_256_abi_vlen_c23(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_least_element(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_least_element(<vscale x 1 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc(1024))) test_vls_least_element(__attribute__((vector_size(8))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_least_element_c23(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_least_element_c23(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc(1024)]] void test_vls_least_element_c23(__attribute__((vector_size(8))) int arg) {}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
index c01aeb21f67571..9447e6fae0cea2 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
@@ -1,6 +1,8 @@
 // REQUIRES: riscv-registered-target
 // RUN: %clang_cc1 -std=c++11 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
+// RUN: %clang_cc1 -std=c++11 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
 
 #include <riscv_vector.h>
 
@@ -30,3 +32,23 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
   __riscv_vse32_v_i32m1(base, val, vl);
   return ret;
 }
+
+// CHECK-LLVM: define dso_local void @_Z14test_vls_no_ccDv4_i(i128 noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local void @_Z14test_vls_no_ccDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
+void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 2 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc(256)]] void test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_vls_least_elementDv2_i(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z22test_vls_least_elementDv2_i(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc(1024)]] void test_vls_least_element(__attribute__((vector_size(8))) int arg) {}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv.c
index 5c35901799b427..da4819186f4e21 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv.c
@@ -15,3 +15,21 @@ void __attribute__((riscv_vector_cc)) test_no_attribute(int x) { } // expected-e
 
 void test_no_attribute2(int); // expected-note {{previous declaration is here}}
 [[riscv::vector_cc]] void test_no_attribute2(int x) { } // expected-error {{function declared 'riscv_vector_cc' here was previously declared without calling convention}}
+
+__attribute__((riscv_vls_cc)) int var_vls; // expected-warning {{'riscv_vls_cc' only applies to function types; type here is 'int'}}
+
+__attribute__((riscv_vls_cc)) void func_vls();
+__attribute__((riscv_vls_cc(1))) void func_vls_invalid(); // expected-error {{argument value 1 is outside the valid range [32, 65536]}} expected-warning {{'riscv_vls_cc' only applies to function types; type here is 'void (void)__attribute__((riscv_vls_cc))'}}
+__attribute__((riscv_vls_cc(129))) void func_vls_invalid(); // expected-error {{argument should be a power of 2}} expected-warning {{'riscv_vls_cc' only applies to function types; type here is 'void (void)__attribute__((riscv_vls_cc))'}}
+
+void test_vls_no_attribute(int); // expected-note {{previous declaration is here}}
+void __attribute__((riscv_vls_cc)) test_vls_no_attribute(int x) { } // expected-error {{function declared 'riscv_vls_cc' here was previously declared without calling convention}}
+
+[[riscv::vls_cc]] int var2_vls; // expected-warning {{'vls_cc' only applies to function types; type here is 'int'}}
+
+[[riscv::vls_cc]] void func2_vls();
+[[riscv::vls_cc(1)]] void func_vls_invalid2(); // expected-error {{argument value 1 is outside the valid range [32, 65536]}} expected-warning {{'vls_cc' only applies to function types; type here is 'void (void)'}}
+[[riscv::vls_cc(129)]] void func_vls_invalid2(); // expected-error {{argument should be a power of 2}} expected-warning {{'vls_cc' only applies to function types; type here is 'void (void)'}}
+
+void test_vls_no_attribute2(int); // expected-note {{previous declaration is here}}
+[[riscv::vls_cc]] void test_vls_no_attribute2(int x) { } // expected-error {{function declared 'riscv_vls_cc' here was previously declared without calling convention}}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv.cpp
index 264bb7d9ad7c00..5e27c76d5307fc 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv.cpp
@@ -33,3 +33,21 @@ void test_lambda2() {
   [[riscv::vector_cc]] auto lambda = []() { // expected-warning {{'vector_cc' only applies to function types; type here is 'auto'}}
   };
 }
+
+[[riscv::vls_cc]] int var_vls; // expected-warning {{'vls_cc' only applies to function types; type here is 'int'}}
+
+[[riscv::vls_cc]] void func_vls();
+[[riscv::vls_cc(1)]] void func_invalid_vls(); // expected-error {{argument value 1 is outside the valid range [32, 65536]}} expected-warning {{'vls_cc' only applies to function types; type here is 'void ()'}}
+[[riscv::vls_cc(129)]] void func_invalid_vls(); // expected-error {{argument should be a power of 2}} expected-warning {{'vls_cc' only applies to function types; type here is 'void ()'}}
+
+void test_no_attribute_vls(int); // expected-note {{previous declaration is here}}
+[[riscv::vls_cc]] void test_no_attribute_vls(int x) { } // expected-error {{function declared 'riscv_vls_cc' here was previously declared without calling convention}}
+
+class test_cc_vls {
+  [[riscv::vls_cc]] void member_func();
+};
+
+void test_lambda_vls() {
+  [[riscv::vls_cc]] auto lambda = []() { // expected-warning {{'vls_cc' only applies to function types; type here is 'auto'}}
+  };
+}
diff --git a/clang/tools/libclang/CXType.cpp b/clang/tools/libclang/CXType.cpp
index b4df12405cf356..070c4203ab5e84 100644
--- a/clang/tools/libclang/CXType.cpp
+++ b/clang/tools/libclang/CXType.cpp
@@ -686,6 +686,7 @@ CXCallingConv clang_getFunctionTypeCallingConv(CXType X) {
       TCALLINGCONV(M68kRTD);
       TCALLINGCONV(PreserveNone);
       TCALLINGCONV(RISCVVectorCall);
+      TCALLINGCONV(RISCVVLSCall);
     case CC_SpirFunction: return CXCallingConv_Unexposed;
     case CC_AMDGPUKernelCall: return CXCallingConv_Unexposed;
     case CC_OpenCLKernel: return CXCallingConv_Unexposed;
diff --git a/llvm/include/llvm/AsmParser/LLToken.h b/llvm/include/llvm/AsmParser/LLToken.h
index 178c911120b4ce..55d5f903ca0d32 100644
--- a/llvm/include/llvm/AsmParser/LLToken.h
+++ b/llvm/include/llvm/AsmParser/LLToken.h
@@ -185,6 +185,7 @@ enum Kind {
   kw_m68k_rtdcc,
   kw_graalcc,
   kw_riscv_vector_cc,
+  kw_riscv_vls_cc,
 
   // Attributes:
   kw_attributes,
diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.def b/llvm/include/llvm/BinaryFormat/Dwarf.def
index 0cbbbe823c06b5..8dd4220b72d345 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.def
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -1116,6 +1116,7 @@ HANDLE_DW_CC(0xcc, LLVM_M68kRTD)
 HANDLE_DW_CC(0xcd, LLVM_PreserveNone)
 HANDLE_DW_CC(0xce, LLVM_RISCVVectorCall)
 HANDLE_DW_CC(0xcf, LLVM_SwiftTail)
+HANDLE_DW_CC(0xd0, LLVM_RISCVVLSCall)
 // From GCC source code (include/dwarf2.h): This DW_CC_ value is not currently
 // generated by any toolchain.  It is used internally to GDB to indicate OpenCL
 // C functions that have been compiled with the IBM XL C for OpenCL compiler and
diff --git a/llvm/include/llvm/IR/CallingConv.h b/llvm/include/llvm/IR/CallingConv.h
index 55e32028e3ed08..bc3a75f2fe6656 100644
--- a/llvm/include/llvm/IR/CallingConv.h
+++ b/llvm/include/llvm/IR/CallingConv.h
@@ -270,6 +270,9 @@ namespace CallingConv {
     /// Preserve X1-X15, X19-X29, SP, Z0-Z31, P0-P15.
     AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1 = 111,
 
+    /// Calling convention used for RISC-V V-extension fixed vectors.
+    RISCV_VLSCall = 112,
+
     /// The highest possible ID. Must be some 2^k - 1.
     MaxID = 1023
   };
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 56abd03d623541..28fe7c55266838 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -656,6 +656,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(m68k_rtdcc);
   KEYWORD(graalcc);
   KEYWORD(riscv_vector_cc);
+  KEYWORD(riscv_vls_cc);
 
   KEYWORD(cc);
   KEYWORD(c);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 8ddb2efb0e26c2..52e351130dd940 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -2205,6 +2205,7 @@ void LLParser::parseOptionalDLLStorageClass(unsigned &Res) {
 ///   ::= 'm68k_rtdcc'
 ///   ::= 'graalcc'
 ///   ::= 'riscv_vector_cc'
+///   ::= 'riscv_vls_cc'
 ///   ::= 'cc' UINT
 ///
 bool LLParser::parseOptionalCallingConv(unsigned &CC) {
@@ -2281,6 +2282,9 @@ bool LLParser::parseOptionalCallingConv(unsigned &CC) {
   case lltok::kw_riscv_vector_cc:
     CC = CallingConv::RISCV_VectorCall;
     break;
+  case lltok::kw_riscv_vls_cc:
+    CC = CallingConv::RISCV_VLSCall;
+    break;
   case lltok::kw_cc: {
       Lex.Lex();
       return parseUInt32(CC);
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index 4bc7d9e68280d5..ebeae8d387f953 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -368,6 +368,9 @@ static void PrintCallingConv(unsigned cc, raw_ostream &Out) {
   case CallingConv::RISCV_VectorCall:
     Out << "riscv_vector_cc";
     break;
+  case CallingConv::RISCV_VLSCall:
+    Out << "riscv_vls_cc";
+    break;
   }
 }
 
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 3b6dd0c11bbf90..4055f30d72165c 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -19460,6 +19460,7 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
   case CallingConv::SPIR_KERNEL:
   case CallingConv::GRAAL:
   case CallingConv::RISCV_VectorCall:
+  case CallingConv::RISCV_VLSCall:
     break;
   case CallingConv::GHC:
     if (Subtarget.hasStdExtE())
diff --git a/llvm/test/Assembler/riscv_vls_cc.ll b/llvm/test/Assembler/riscv_vls_cc.ll
new file mode 100644
index 00000000000000..cc63e61ed6a1f7
--- /dev/null
+++ b/llvm/test/Assembler/riscv_vls_cc.ll
@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+; RUN: verify-uselistorder %s
+
+; CHECK: define riscv_vls_cc void @no_args() {
+define riscv_vls_cc void @no_args() {
+  ret void
+}
+
+; CHECK: define riscv_vls_cc void @byval_arg(ptr byval(i32) %0) {
+define riscv_vls_cc void @byval_arg(ptr byval(i32)) {
+  ret void
+}
diff --git a/llvm/test/Bitcode/compatibility.ll b/llvm/test/Bitcode/compatibility.ll
index a849789da536ac..f814408dbddc3f 100644
--- a/llvm/test/Bitcode/compatibility.ll
+++ b/llvm/test/Bitcode/compatibility.ll
@@ -516,6 +516,10 @@ declare cc96 void @f.cc96()
 ; CHECK: declare amdgpu_es void @f.cc96()
 declare amdgpu_es void @f.amdgpu_es()
 ; CHECK: declare amdgpu_es void @f.amdgpu_es()
+declare cc112 void @f.cc112()
+; CHECK: declare riscv_vls_cc void @f.cc112()
+declare riscv_vls_cc void @riscv_vls_cc()
+; CHECK: declare riscv_vls_cc void @riscv_vls_cc()
 declare cc1023 void @f.cc1023()
 ; CHECK: declare cc1023 void @f.cc1023()
 

>From 14a75f09362dd05f941d7a1a60858e15174537cd Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Sat, 9 Nov 2024 18:58:14 -0800
Subject: [PATCH 2/6] fixup! [RISCV][VLS] Support RISCV VLS calling convention

---
 clang/lib/CodeGen/Targets/RISCV.cpp | 2 +-
 clang/lib/Sema/SemaDeclAttr.cpp     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index 35763b824a7168..b1601a76e4b703 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -421,7 +421,7 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
     }
 
     // Generic vector
-    // The number of element need to be at least 1.
+    // The number of elements needs to be at least 1.
     ResType = llvm::ScalableVectorType::get(
         EltType,
         llvm::divideCeil(NumElts * llvm::RISCV::RVVBitsPerBlock, ArgABIVLen));
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 2d1885bec36280..18ff259449d6e0 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -4994,7 +4994,7 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   }
 
   if (Attrs.getKind() == ParsedAttr::AT_RISCVVLSCC) {
-    // riscv_vls_cc only accept 0 or 1 argument.
+    // riscv_vls_cc only accepts 0 or 1 argument.
     if (!Attrs.checkAtLeastNumArgs(*this, 0) ||
         !Attrs.checkAtMostNumArgs(*this, 1)) {
       Attrs.setInvalid();

>From 65361ab9c6f9a97138bb482f110cdbba701af074 Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Tue, 3 Dec 2024 23:28:32 -0800
Subject: [PATCH 3/6] fixup! [RISCV][VLS] Support RISCV VLS calling convention

---
 clang/lib/CodeGen/Targets/RISCV.cpp           | 13 +++++++---
 clang/lib/Sema/SemaType.cpp                   |  7 ++---
 .../RISCV/riscv-vector-callingconv-llvm-ir.c  | 26 ++++++++++++++-----
 .../riscv-vector-callingconv-llvm-ir.cpp      | 16 +++++++++---
 4 files changed, 44 insertions(+), 18 deletions(-)

diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index b1601a76e4b703..093ef52c7595ea 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -114,8 +114,13 @@ void RISCVABIInfo::appendAttributeMangling(StringRef AttrStr,
 
 void RISCVABIInfo::computeInfo(CGFunctionInfo &FI) const {
   unsigned ArgABIVLen = 1 << FI.getExtInfo().getLog2RISCVABIVLen();
-  if (ArgABIVLen == 1)
+  // If ArgABIVLen is default value(2), try to set it to the value passed by
+  // option if any, otherwise, set it to default value 128.
+  // Note that ArgABIVLen == 1 means vector_cc is not enabled.
+  if (ArgABIVLen == 2 && ABIVLen)
     ArgABIVLen = ABIVLen;
+  else if (ArgABIVLen == 2)
+    ArgABIVLen = 128;
 
   QualType RetTy = FI.getReturnType();
   if (!getCXXABI().classifyReturnType(FI))
@@ -416,8 +421,8 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
         (EltType->isDoubleTy() && !TI.hasFeature("zve64d")) ||
         (EltType->isIntegerTy(64) && !TI.hasFeature("zve64x")) ||
         EltType->isIntegerTy(128)) {
-      NumElts = NumElts * EltType->getScalarSizeInBits() / 32;
-      EltType = llvm::Type::getInt32Ty(getVMContext());
+      EltType =
+          llvm::Type::getIntNTy(getVMContext(), EltType->getScalarSizeInBits());
     }
 
     // Generic vector
@@ -543,7 +548,7 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_2 ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_4)
       return coerceVLSVector(Ty);
-    if (VT->getVectorKind() == VectorKind::Generic && ArgABIVLen != 0)
+    if (VT->getVectorKind() == VectorKind::Generic && ArgABIVLen != 1)
       // Generic vector without riscv_vls_cc should fall through and pass by
       // reference.
       return coerceVLSVector(Ty, ArgABIVLen);
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 0b1f7f51bc05c6..f12eba7c312005 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8035,12 +8035,13 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
   Attr *CCAttr = getCCTypeAttr(S.Context, attr);
 
   if (attr.getKind() == ParsedAttr::AT_RISCVVLSCC) {
-    // If the riscv_abi_vlen doesn't have any argument, default ABI_VLEN is 128.
-    unsigned ABIVLen = 128;
+    // If the riscv_abi_vlen doesn't have any argument, we set set it to 2 to
+    // differentiate from functions without attribute.
+    unsigned ABIVLen = 2;
     if (attr.getNumArgs() &&
         !S.checkUInt32Argument(attr, attr.getArgAsExpr(0), ABIVLen))
       return false;
-    if (ABIVLen < 32 || ABIVLen > 65536) {
+    if (ABIVLen != 2 && (ABIVLen < 32 || ABIVLen > 65536)) {
       S.Diag(attr.getLoc(), diag::err_argument_invalid_range)
           << ABIVLen << 32 << 65536;
       return false;
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
index 8c205459db9993..0b06bede29dc76 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
@@ -1,10 +1,14 @@
 // REQUIRES: riscv-registered-target
 // RUN: %clang_cc1 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
+// RUN: %clang_cc1 -triple riscv64 -target-feature +zve32x \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ZVE32X %s
 // RUN: %clang_cc1 -std=c23 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
 // RUN: %clang_cc1 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
+// RUN: %clang_cc1 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +zve32x \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN-ZVE32X %s
 // RUN: %clang_cc1 -std=c23 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
 
@@ -38,25 +42,33 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
 }
 
 // CHECK-LLVM: define dso_local void @test_vls_no_cc(i128 noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local void @test_vls_no_cc(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local void @test_vls_no_cc(i128 noundef %arg.coerce)
 void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_c23(__attribute__((vector_size(16))) int arg) {}
 
-// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 4 x i16> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i16> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
-// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 4 x i16> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i16> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_c23_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
+// CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature_zve32x(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature_zve32x(<vscale x 1 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
+
+// CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
+
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
 // CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc(256))) test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
index 9447e6fae0cea2..0b91f8b3877eb2 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
@@ -1,8 +1,12 @@
 // REQUIRES: riscv-registered-target
 // RUN: %clang_cc1 -std=c++11 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
+// RUN: %clang_cc1 -std=c++11 -triple riscv64 -target-feature +zve32x \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ZVE32X %s
 // RUN: %clang_cc1 -std=c++11 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
+// RUN: %clang_cc1 -std=c++11 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +zve32x \
+// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN-ZVE32X %s
 
 #include <riscv_vector.h>
 
@@ -34,17 +38,21 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
 }
 
 // CHECK-LLVM: define dso_local void @_Z14test_vls_no_ccDv4_i(i128 noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local void @_Z14test_vls_no_ccDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local void @_Z14test_vls_no_ccDv4_i(i128 noundef %arg.coerce)
 void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
-// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 4 x i16> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i16> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
+// CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @_Z52test_vls_default_abi_vlen_unsupported_feature_zve32xDv4_f(<vscale x 2 x i32> noundef %arg.coerce)
+// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @_Z52test_vls_default_abi_vlen_unsupported_feature_zve32xDv4_f(<vscale x 1 x i32> noundef %arg.coerce)
+[[riscv::vls_cc]] void test_vls_default_abi_vlen_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
+
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
 // CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(256)]] void test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}

>From b10ff510e98672503fe434f6310828d1d5c705df Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Mon, 9 Dec 2024 10:04:07 -0800
Subject: [PATCH 4/6] fixup! [RISCV][VLS] Support RISCV VLS calling convention

---
 clang/lib/Sema/SemaType.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index f12eba7c312005..cd70a8f0230d90 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8041,7 +8041,7 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
     if (attr.getNumArgs() &&
         !S.checkUInt32Argument(attr, attr.getArgAsExpr(0), ABIVLen))
       return false;
-    if (ABIVLen != 2 && (ABIVLen < 32 || ABIVLen > 65536)) {
+    if (attr.getNumArgs() && (ABIVLen < 32 || ABIVLen > 65536)) {
       S.Diag(attr.getLoc(), diag::err_argument_invalid_range)
           << ABIVLen << 32 << 65536;
       return false;

>From 6b76dbc1c06c1516f234a6cffbd271ee2dd46cd7 Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Sun, 22 Dec 2024 23:10:58 -0800
Subject: [PATCH 5/6] fixup! Remove command line option

---
 clang/include/clang/Basic/CodeGenOptions.def  |  3 --
 clang/include/clang/Driver/Options.td         |  4 --
 clang/lib/CodeGen/CodeGenModule.cpp           |  3 +-
 clang/lib/CodeGen/TargetInfo.h                |  2 +-
 clang/lib/CodeGen/Targets/RISCV.cpp           | 50 ++++++++-----------
 clang/lib/Driver/ToolChains/Arch/RISCV.cpp    |  4 --
 clang/lib/Driver/ToolChains/Clang.cpp         | 15 ------
 clang/lib/Sema/SemaType.cpp                   |  6 +--
 .../RISCV/riscv-vector-callingconv-llvm-ir.c  | 17 -------
 .../riscv-vector-callingconv-llvm-ir.cpp      | 10 ----
 10 files changed, 25 insertions(+), 89 deletions(-)

diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 894aaff054b631..e45370bde74a5d 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -464,9 +464,6 @@ ENUM_CODEGENOPT(ZeroCallUsedRegs, llvm::ZeroCallUsedRegs::ZeroCallUsedRegsKind,
 /// non-deleting destructors. (No effect on Microsoft ABI.)
 CODEGENOPT(CtorDtorReturnThis, 1, 0)
 
-/// Specify the VLEN for VLS calling convention.
-CODEGENOPT(RISCVABIVLen, 17, 0)
-
 /// FIXME: Make DebugOptions its own top-level .def file.
 #include "DebugOptions.def"
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index eeac988ba5ead9..7da0d3902e2166 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4950,10 +4950,6 @@ def mrvv_vector_bits_EQ : Joined<["-"], "mrvv-vector-bits=">, Group<m_Group>,
       !eq(GlobalDocumentation.Program, "Flang") : "",
       true: " The value will be reflected in __riscv_v_fixed_vlen preprocessor define"),
     " (RISC-V only)")>;
-def mriscv_abi_vlen_EQ : Joined<["-"], "mriscv-abi-vlen=">, Group<m_Group>,
-  Visibility<[ClangOption, CC1Option]>,
-  HelpText<"Specify the VLEN for VLS calling convention.">,
-  MarshallingInfoInt<CodeGenOpts<"RISCVABIVLen">>;
 def munaligned_access : Flag<["-"], "munaligned-access">, Group<m_Group>,
   HelpText<"Allow memory accesses to be unaligned (AArch32/MIPSr6 only)">;
 def mno_unaligned_access : Flag<["-"], "mno-unaligned-access">, Group<m_Group>,
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index dcb43b3da26af8..ba376f9ecfacde 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -234,8 +234,7 @@ createTargetCodeGenInfo(CodeGenModule &CGM) {
     else if (ABIStr.ends_with("d"))
       ABIFLen = 64;
     bool EABI = ABIStr.ends_with("e");
-    return createRISCVTargetCodeGenInfo(CGM, XLen, ABIFLen,
-                                        CodeGenOpts.RISCVABIVLen, EABI);
+    return createRISCVTargetCodeGenInfo(CGM, XLen, ABIFLen, EABI);
   }
 
   case llvm::Triple::systemz: {
diff --git a/clang/lib/CodeGen/TargetInfo.h b/clang/lib/CodeGen/TargetInfo.h
index e94d04f1159404..373f8b8a80fdb1 100644
--- a/clang/lib/CodeGen/TargetInfo.h
+++ b/clang/lib/CodeGen/TargetInfo.h
@@ -533,7 +533,7 @@ createPPC64_SVR4_TargetCodeGenInfo(CodeGenModule &CGM, PPC64_SVR4_ABIKind Kind,
 
 std::unique_ptr<TargetCodeGenInfo>
 createRISCVTargetCodeGenInfo(CodeGenModule &CGM, unsigned XLen, unsigned FLen,
-                             unsigned ABIVLen, bool EABI);
+                             bool EABI);
 
 std::unique_ptr<TargetCodeGenInfo>
 createCommonSPIRTargetCodeGenInfo(CodeGenModule &CGM);
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index 093ef52c7595ea..fd75a7b2666f9d 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -26,7 +26,6 @@ class RISCVABIInfo : public DefaultABIInfo {
   // ISA might have a wider FLen than the selected ABI (e.g. an RV32IF target
   // with soft float ABI has FLen==0).
   unsigned FLen;
-  unsigned ABIVLen;
   const int NumArgGPRs;
   const int NumArgFPRs;
   const bool EABI;
@@ -38,8 +37,8 @@ class RISCVABIInfo : public DefaultABIInfo {
 
 public:
   RISCVABIInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen, unsigned FLen,
-               unsigned ABIVLen, bool EABI)
-      : DefaultABIInfo(CGT), XLen(XLen), FLen(FLen), ABIVLen(ABIVLen),
+               bool EABI)
+      : DefaultABIInfo(CGT), XLen(XLen), FLen(FLen),
         NumArgGPRs(EABI ? 6 : 8), NumArgFPRs(FLen != 0 ? 8 : 0), EABI(EABI) {}
 
   // DefaultABIInfo's classifyReturnType and classifyArgumentType are
@@ -47,8 +46,8 @@ class RISCVABIInfo : public DefaultABIInfo {
   void computeInfo(CGFunctionInfo &FI) const override;
 
   ABIArgInfo classifyArgumentType(QualType Ty, bool IsFixed, int &ArgGPRsLeft,
-                                  int &ArgFPRsLeft, unsigned ArgABIVLen) const;
-  ABIArgInfo classifyReturnType(QualType RetTy, unsigned ArgABIVLen) const;
+                                  int &ArgFPRsLeft, unsigned ABIVLen) const;
+  ABIArgInfo classifyReturnType(QualType RetTy, unsigned ABIVLen) const;
 
   RValue EmitVAArg(CodeGenFunction &CGF, Address VAListAddr, QualType Ty,
                    AggValueSlot Slot) const override;
@@ -64,7 +63,7 @@ class RISCVABIInfo : public DefaultABIInfo {
                                                llvm::Type *Field2Ty,
                                                CharUnits Field2Off) const;
 
-  ABIArgInfo coerceVLSVector(QualType Ty, unsigned ArgABIVLen = 0) const;
+  ABIArgInfo coerceVLSVector(QualType Ty, unsigned ABIVLen = 0) const;
 
   using ABIInfo::appendAttributeMangling;
   void appendAttributeMangling(TargetClonesAttr *Attr, unsigned Index,
@@ -113,18 +112,10 @@ void RISCVABIInfo::appendAttributeMangling(StringRef AttrStr,
 }
 
 void RISCVABIInfo::computeInfo(CGFunctionInfo &FI) const {
-  unsigned ArgABIVLen = 1 << FI.getExtInfo().getLog2RISCVABIVLen();
-  // If ArgABIVLen is default value(2), try to set it to the value passed by
-  // option if any, otherwise, set it to default value 128.
-  // Note that ArgABIVLen == 1 means vector_cc is not enabled.
-  if (ArgABIVLen == 2 && ABIVLen)
-    ArgABIVLen = ABIVLen;
-  else if (ArgABIVLen == 2)
-    ArgABIVLen = 128;
-
+  unsigned ABIVLen = 1 << FI.getExtInfo().getLog2RISCVABIVLen();
   QualType RetTy = FI.getReturnType();
   if (!getCXXABI().classifyReturnType(FI))
-    FI.getReturnInfo() = classifyReturnType(RetTy, ArgABIVLen);
+    FI.getReturnInfo() = classifyReturnType(RetTy, ABIVLen);
 
   // IsRetIndirect is true if classifyArgumentType indicated the value should
   // be passed indirect, or if the type size is a scalar greater than 2*XLen
@@ -151,7 +142,7 @@ void RISCVABIInfo::computeInfo(CGFunctionInfo &FI) const {
   for (auto &ArgInfo : FI.arguments()) {
     bool IsFixed = ArgNum < NumFixedArgs;
     ArgInfo.info = classifyArgumentType(ArgInfo.type, IsFixed, ArgGPRsLeft,
-                                        ArgFPRsLeft, ArgABIVLen);
+                                        ArgFPRsLeft, ABIVLen);
     ArgNum++;
   }
 }
@@ -373,7 +364,7 @@ ABIArgInfo RISCVABIInfo::coerceAndExpandFPCCEligibleStruct(
 // Fixed-length RVV vectors are represented as scalable vectors in function
 // args/return and must be coerced from fixed vectors.
 ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
-                                         unsigned ArgABIVLen) const {
+                                         unsigned ABIVLen) const {
   assert(Ty->isVectorType() && "expected vector type!");
 
   const auto *VT = Ty->castAs<VectorType>();
@@ -405,7 +396,7 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
 
   llvm::ScalableVectorType *ResType;
 
-  if (ArgABIVLen == 0) {
+  if (ABIVLen == 0) {
     // The MinNumElts is simplified from equation:
     // NumElts / VScale =
     //  (EltSize * NumElts / (VScale * RVVBitsPerBlock))
@@ -429,7 +420,7 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
     // The number of elements needs to be at least 1.
     ResType = llvm::ScalableVectorType::get(
         EltType,
-        llvm::divideCeil(NumElts * llvm::RISCV::RVVBitsPerBlock, ArgABIVLen));
+        llvm::divideCeil(NumElts * llvm::RISCV::RVVBitsPerBlock, ABIVLen));
   }
 
   return ABIArgInfo::getDirect(ResType);
@@ -438,7 +429,7 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
 ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
                                               int &ArgGPRsLeft,
                                               int &ArgFPRsLeft,
-                                              unsigned ArgABIVLen) const {
+                                              unsigned ABIVLen) const {
   assert(ArgGPRsLeft <= NumArgGPRs && "Arg GPR tracking underflow");
   Ty = useFirstFieldIfTransparentUnion(Ty);
 
@@ -548,10 +539,10 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_2 ||
         VT->getVectorKind() == VectorKind::RVVFixedLengthMask_4)
       return coerceVLSVector(Ty);
-    if (VT->getVectorKind() == VectorKind::Generic && ArgABIVLen != 1)
+    if (VT->getVectorKind() == VectorKind::Generic && ABIVLen != 1)
       // Generic vector without riscv_vls_cc should fall through and pass by
       // reference.
-      return coerceVLSVector(Ty, ArgABIVLen);
+      return coerceVLSVector(Ty, ABIVLen);
   }
 
   // Aggregates which are <= 2*XLen will be passed in registers if possible,
@@ -576,7 +567,7 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
 }
 
 ABIArgInfo RISCVABIInfo::classifyReturnType(QualType RetTy,
-                                            unsigned ArgABIVLen) const {
+                                            unsigned ABIVLen) const {
   if (RetTy->isVoidType())
     return ABIArgInfo::getIgnore();
 
@@ -586,7 +577,7 @@ ABIArgInfo RISCVABIInfo::classifyReturnType(QualType RetTy,
   // The rules for return and argument types are the same, so defer to
   // classifyArgumentType.
   return classifyArgumentType(RetTy, /*IsFixed=*/true, ArgGPRsLeft, ArgFPRsLeft,
-                              ArgABIVLen);
+                              ABIVLen);
 }
 
 RValue RISCVABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
@@ -625,9 +616,9 @@ namespace {
 class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
 public:
   RISCVTargetCodeGenInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen,
-                         unsigned FLen, unsigned ABIVLen, bool EABI)
+                         unsigned FLen, bool EABI)
       : TargetCodeGenInfo(
-            std::make_unique<RISCVABIInfo>(CGT, XLen, FLen, ABIVLen, EABI)) {
+            std::make_unique<RISCVABIInfo>(CGT, XLen, FLen, EABI)) {
     SwiftInfo =
         std::make_unique<SwiftABIInfo>(CGT, /*SwiftErrorInRegister=*/false);
   }
@@ -659,8 +650,7 @@ class RISCVTargetCodeGenInfo : public TargetCodeGenInfo {
 
 std::unique_ptr<TargetCodeGenInfo>
 CodeGen::createRISCVTargetCodeGenInfo(CodeGenModule &CGM, unsigned XLen,
-                                      unsigned FLen, unsigned ABIVLen,
-                                      bool EABI) {
+                                      unsigned FLen, bool EABI) {
   return std::make_unique<RISCVTargetCodeGenInfo>(CGM.getTypes(), XLen, FLen,
-                                                  ABIVLen, EABI);
+                                                  EABI);
 }
diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
index 18da247b3eab48..6935904a24edbf 100644
--- a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -95,10 +95,6 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
       CPUFastVectorUnaligned = true;
   }
 
-  if (Arg *A = Args.getLastArg(options::OPT_mriscv_abi_vlen_EQ))
-    Features.push_back(
-        Args.MakeArgString(Twine("+abi-vlen-") + A->getValue() + "b"));
-
 // Handle features corresponding to "-ffixed-X" options
 #define RESERVE_REG(REG)                                                       \
   if (Args.hasArg(options::OPT_ffixed_##REG))                                  \
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 89749b64a3dfd9..dca8d3fd7b3eaf 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2203,21 +2203,6 @@ void Clang::AddRISCVTargetArgs(const ArgList &Args,
           << A->getSpelling() << Val;
     }
   }
-
-  if (Arg *A = Args.getLastArg(options::OPT_mriscv_abi_vlen_EQ)) {
-    StringRef ABIVLenStr = A->getValue();
-    unsigned ABIVLen;
-    const Driver &D = getToolChain().getDriver();
-    if (ABIVLenStr.getAsInteger(10, ABIVLen) || ABIVLen < 32 ||
-        ABIVLen > 65536 || !llvm::isPowerOf2_64(ABIVLen)) {
-      D.Diag(diag::err_drv_invalid_value)
-          << A->getOption().getName() << ABIVLenStr;
-      return;
-    }
-
-    CmdArgs.push_back(
-        Args.MakeArgString(Twine("-mriscv-abi-vlen=") + A->getValue()));
-  }
 }
 
 void Clang::AddSparcTargetArgs(const ArgList &Args,
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index cd70a8f0230d90..827024477cf12b 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8035,9 +8035,9 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
   Attr *CCAttr = getCCTypeAttr(S.Context, attr);
 
   if (attr.getKind() == ParsedAttr::AT_RISCVVLSCC) {
-    // If the riscv_abi_vlen doesn't have any argument, we set set it to 2 to
-    // differentiate from functions without attribute.
-    unsigned ABIVLen = 2;
+    // If the riscv_abi_vlen doesn't have any argument, we set set it to default
+    // value 128.
+    unsigned ABIVLen = 128;
     if (attr.getNumArgs() &&
         !S.checkUInt32Argument(attr, attr.getArgAsExpr(0), ABIVLen))
       return false;
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
index 0b06bede29dc76..3cb1fa0407d8a8 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
@@ -5,12 +5,6 @@
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ZVE32X %s
 // RUN: %clang_cc1 -std=c23 -triple riscv64 -target-feature +v \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
-// RUN: %clang_cc1 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
-// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
-// RUN: %clang_cc1 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +zve32x \
-// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN-ZVE32X %s
-// RUN: %clang_cc1 -std=c23 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
-// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
 
 #include <riscv_vector.h>
 
@@ -42,45 +36,34 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
 }
 
 // CHECK-LLVM: define dso_local void @test_vls_no_cc(i128 noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local void @test_vls_no_cc(i128 noundef %arg.coerce)
 void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_c23(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 4 x i16> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature(<vscale x 2 x i16> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 4 x i16> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature(<vscale x 2 x i16> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_c23_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
 // CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature_zve32x(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_unsupported_feature_zve32x(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc)) test_vls_default_abi_vlen_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
 
 // CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_c23_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc(256))) test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_256_abi_vlen_c23(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(256)]] void test_vls_256_abi_vlen_c23(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_least_element(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_least_element(<vscale x 1 x i32> noundef %arg.coerce)
 void __attribute__((riscv_vls_cc(1024))) test_vls_least_element(__attribute__((vector_size(8))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_least_element_c23(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @test_vls_least_element_c23(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(1024)]] void test_vls_least_element_c23(__attribute__((vector_size(8))) int arg) {}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
index 0b91f8b3877eb2..4265e129c2fdb8 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
@@ -3,10 +3,6 @@
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM %s
 // RUN: %clang_cc1 -std=c++11 -triple riscv64 -target-feature +zve32x \
 // RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ZVE32X %s
-// RUN: %clang_cc1 -std=c++11 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +v \
-// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN %s
-// RUN: %clang_cc1 -std=c++11 -triple riscv64 -mriscv-abi-vlen=256 -target-feature +zve32x \
-// RUN:   -emit-llvm %s -o - | FileCheck -check-prefix=CHECK-LLVM-ABI-VLEN-ZVE32X %s
 
 #include <riscv_vector.h>
 
@@ -38,25 +34,19 @@ vint32m1_t test_no_vector_cc_attr(vint32m1_t input, int32_t *base, size_t vl) {
 }
 
 // CHECK-LLVM: define dso_local void @_Z14test_vls_no_ccDv4_i(i128 noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local void @_Z14test_vls_no_ccDv4_i(i128 noundef %arg.coerce)
 void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z25test_vls_default_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 4 x i16> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z45test_vls_default_abi_vlen_unsupported_featureDv8_DF16_(<vscale x 2 x i16> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_unsupported_feature(__attribute__((vector_size(16))) _Float16 arg) {}
 
 // CHECK-LLVM-ZVE32X: define dso_local riscv_vls_cc void @_Z52test_vls_default_abi_vlen_unsupported_feature_zve32xDv4_f(<vscale x 2 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN-ZVE32X: define dso_local riscv_vls_cc void @_Z52test_vls_default_abi_vlen_unsupported_feature_zve32xDv4_f(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc]] void test_vls_default_abi_vlen_unsupported_feature_zve32x(__attribute__((vector_size(16))) float arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z21test_vls_256_abi_vlenDv4_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(256)]] void test_vls_256_abi_vlen(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_vls_least_elementDv2_i(<vscale x 1 x i32> noundef %arg.coerce)
-// CHECK-LLVM-ABI-VLEN: define dso_local riscv_vls_cc void @_Z22test_vls_least_elementDv2_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(1024)]] void test_vls_least_element(__attribute__((vector_size(8))) int arg) {}

>From 68d23382c970fdf4520fc7eab8089cad854b87ee Mon Sep 17 00:00:00 2001
From: Brandon Wu <brandon.wu at sifive.com>
Date: Sun, 5 Jan 2025 22:25:17 -0800
Subject: [PATCH 6/6] fixup! handle struct and minor fixup

---
 clang/lib/CodeGen/CGCall.cpp                  |  27 ++-
 clang/lib/CodeGen/Targets/RISCV.cpp           | 160 +++++++++++++++++-
 .../RISCV/riscv-vector-callingconv-llvm-ir.c  | 108 ++++++++++++
 .../riscv-vector-callingconv-llvm-ir.cpp      | 108 ++++++++++++
 4 files changed, 384 insertions(+), 19 deletions(-)

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 816c5ebc18623c..e6f927358b0105 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3239,24 +3239,19 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
         }
       }
 
-      llvm::StructType *STy =
-          dyn_cast<llvm::StructType>(ArgI.getCoerceToType());
-      if (ArgI.isDirect() && !ArgI.getCanBeFlattened() && STy &&
-          STy->getNumElements() > 1) {
-        [[maybe_unused]] llvm::TypeSize StructSize =
-            CGM.getDataLayout().getTypeAllocSize(STy);
-        [[maybe_unused]] llvm::TypeSize PtrElementSize =
-            CGM.getDataLayout().getTypeAllocSize(ConvertTypeForMem(Ty));
-        if (STy->containsHomogeneousScalableVectorTypes()) {
-          assert(StructSize == PtrElementSize &&
-                 "Only allow non-fractional movement of structure with"
-                 "homogeneous scalable vector type");
-
-          ArgVals.push_back(ParamValue::forDirect(AI));
-          break;
-        }
+      // Struct of fixed-length vectors and struct of array of fixed-length
+      // vector in VLS calling convention are coerced to vector tuple
+      // type(represented as TargetExtType) and scalable vector type
+      // respectively, they're no longer handled as struct.
+      if (ArgI.isDirect() && isa<llvm::StructType>(ConvertType(Ty)) &&
+          (isa<llvm::TargetExtType>(ArgI.getCoerceToType()) ||
+           isa<llvm::ScalableVectorType>(ArgI.getCoerceToType()))) {
+        ArgVals.push_back(ParamValue::forDirect(AI));
+        break;
       }
 
+      llvm::StructType *STy =
+          dyn_cast<llvm::StructType>(ArgI.getCoerceToType());
       Address Alloca = CreateMemTemp(Ty, getContext().getDeclAlign(Arg),
                                      Arg->getName());
 
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index fd75a7b2666f9d..28b5540b6cbb5d 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -35,6 +35,9 @@ class RISCVABIInfo : public DefaultABIInfo {
                                       llvm::Type *&Field2Ty,
                                       CharUnits &Field2Off) const;
 
+  bool detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
+                                 llvm::Type *&VLSType) const;
+
 public:
   RISCVABIInfo(CodeGen::CodeGenTypes &CGT, unsigned XLen, unsigned FLen,
                bool EABI)
@@ -361,6 +364,149 @@ ABIArgInfo RISCVABIInfo::coerceAndExpandFPCCEligibleStruct(
   return ABIArgInfo::getCoerceAndExpand(CoerceToType, UnpaddedCoerceToType);
 }
 
+bool RISCVABIInfo::detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
+                                             llvm::Type *&VLSType) const {
+  // No riscv_vls_cc attribute.
+  if (ABIVLen == 1)
+    return false;
+
+  // Legal struct for VLS calling convention should fulfill following rules:
+  // 1. Struct element should be either "homogeneous fixed-length vectors" or "a
+  //    fixed-length vector array".
+  // 2. Number of struct elements or array elements should be power of 2.
+  // 3. Total number of vector registers needed should not exceed 8.
+  //
+  // Examples: Assume ABI_VLEN = 128.
+  // These are legal structs:
+  //   a. Structs with 1, 2, 4 or 8 "same" fixed-length vectors, e.g.
+  //   struct {
+  //     __attribute__((vector_size(16))) int a;
+  //     __attribute__((vector_size(16))) int b;
+  //   }
+  //
+  //   b. Structs with "single" fixed-length vector array with lengh 1, 2, 4
+  //   or 8, e.g.
+  //   struct {
+  //     __attribute__((vector_size(16))) int a[2];
+  //   }
+  // These are illegal structs:
+  //   a. Structs with 3 fixed-length vectors, e.g.
+  //   struct {
+  //     __attribute__((vector_size(16))) int a;
+  //     __attribute__((vector_size(16))) int b;
+  //     __attribute__((vector_size(16))) int c;
+  //   }
+  //
+  //   b. Structs with "multiple" fixed-length vector array, e.g.
+  //   struct {
+  //     __attribute__((vector_size(16))) int a[2];
+  //     __attribute__((vector_size(16))) int b[2];
+  //   }
+  //
+  //   c. Vector registers needed exceeds 8, e.g.
+  //   struct {
+  //     // Registers needed for single fixed-length element:
+  //     // 64 * 8 / ABI_VLEN = 4
+  //     __attribute__((vector_size(64))) int a;
+  //     __attribute__((vector_size(64))) int b;
+  //     __attribute__((vector_size(64))) int c;
+  //     __attribute__((vector_size(64))) int d;
+  //   }
+  //
+  // Struct of 1 fixed-length vector is passed as a scalable vector.
+  // Struct of >1 fixed-length vectors are passed as vector tuple.
+  // Struct of 1 array of fixed-length vectors is passed as a scalable vector.
+  // Otherwise, pass the struct indirectly.
+
+  if (llvm::StructType *STy = dyn_cast<llvm::StructType>(CGT.ConvertType(Ty))) {
+    int NumElts = STy->getStructNumElements();
+    if (NumElts > 8 || !llvm::isPowerOf2_32(NumElts))
+      return false;
+
+    auto *FirstEltTy = STy->getElementType(0);
+    if (!STy->containsHomogeneousTypes())
+      return false;
+
+    // Check structure of fixed-length vectors and turn them into vector tuple
+    // type if legal.
+    if (auto *FixedVecTy = dyn_cast<llvm::FixedVectorType>(FirstEltTy)) {
+      if (NumElts == 1) {
+        // Handle single fixed-length vector.
+        VLSType = llvm::ScalableVectorType::get(
+            FixedVecTy->getElementType(),
+            llvm::divideCeil(FixedVecTy->getNumElements() *
+                                 llvm::RISCV::RVVBitsPerBlock,
+                             ABIVLen));
+        // Check registers needed <= 8.
+        return llvm::divideCeil(
+                   FixedVecTy->getNumElements() *
+                       FixedVecTy->getElementType()->getScalarSizeInBits(),
+                   ABIVLen) <= 8;
+      }
+      // LMUL
+      // = fixed-length vector size / ABIVLen
+      // = 8 * I8EltCount / RVVBitsPerBlock
+      // =>
+      // I8EltCount
+      // = (fixed-length vector size * RVVBitsPerBlock) / (ABIVLen * 8)
+      unsigned I8EltCount = llvm::divideCeil(
+          FixedVecTy->getNumElements() *
+              FixedVecTy->getElementType()->getScalarSizeInBits() *
+              llvm::RISCV::RVVBitsPerBlock,
+          ABIVLen * 8);
+      VLSType = llvm::TargetExtType::get(
+          getVMContext(), "riscv.vector.tuple",
+          llvm::ScalableVectorType::get(llvm::Type::getInt8Ty(getVMContext()),
+                                        I8EltCount),
+          NumElts);
+      // Check registers needed <= 8.
+      return NumElts *
+                 llvm::divideCeil(
+                     FixedVecTy->getNumElements() *
+                         FixedVecTy->getElementType()->getScalarSizeInBits(),
+                     ABIVLen) <=
+             8;
+    }
+
+    // If elements are not fixed-length vectors, it should be an array.
+    if (NumElts != 1)
+      return false;
+
+    // Check array of fixed-length vector and turn it into scalable vector type
+    // if legal.
+    if (auto *ArrTy = dyn_cast<llvm::ArrayType>(FirstEltTy)) {
+      int NumArrElt = ArrTy->getNumElements();
+      if (NumArrElt > 8 || !llvm::isPowerOf2_32(NumArrElt))
+        return false;
+
+      auto *ArrEltTy = dyn_cast<llvm::FixedVectorType>(ArrTy->getElementType());
+      if (!ArrEltTy)
+        return false;
+
+      // LMUL
+      // = NumArrElt * fixed-length vector size / ABIVLen
+      // = fixed-length vector elt size * ScalVecNumElts / RVVBitsPerBlock
+      // =>
+      // ScalVecNumElts
+      // = (NumArrElt * fixed-length vector size * RVVBitsPerBlock) /
+      //   (ABIVLen * fixed-length vector elt size)
+      // = NumArrElt * num fixed-length vector elt * RVVBitsPerBlock /
+      //   ABIVLen
+      unsigned ScalVecNumElts = llvm::divideCeil(
+          NumArrElt * ArrEltTy->getNumElements() * llvm::RISCV::RVVBitsPerBlock,
+          ABIVLen);
+      VLSType = llvm::ScalableVectorType::get(ArrEltTy->getElementType(),
+                                              ScalVecNumElts);
+      // Check registers needed <= 8.
+      return llvm::divideCeil(
+                 ScalVecNumElts *
+                     ArrEltTy->getElementType()->getScalarSizeInBits(),
+                 llvm::RISCV::RVVBitsPerBlock) <= 8;
+    }
+  }
+  return false;
+}
+
 // Fixed-length RVV vectors are represented as scalable vectors in function
 // args/return and must be coerced from fixed vectors.
 ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
@@ -410,11 +556,13 @@ ABIArgInfo RISCVABIInfo::coerceVLSVector(QualType Ty,
         (EltType->isBFloatTy() && !TI.hasFeature("zvfbfmin")) ||
         (EltType->isFloatTy() && !TI.hasFeature("zve32f")) ||
         (EltType->isDoubleTy() && !TI.hasFeature("zve64d")) ||
-        (EltType->isIntegerTy(64) && !TI.hasFeature("zve64x")) ||
-        EltType->isIntegerTy(128)) {
+        EltType->isIntegerTy(128))
       EltType =
           llvm::Type::getIntNTy(getVMContext(), EltType->getScalarSizeInBits());
-    }
+
+    // Check registers needed <= 8.
+    if ((EltType->getScalarSizeInBits() * NumElts / ABIVLen) > 8)
+      return getNaturalAlignIndirect(Ty, /*ByVal=*/false);
 
     // Generic vector
     // The number of elements needs to be at least 1.
@@ -485,6 +633,12 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
     }
   }
 
+  if (IsFixed && Ty->isStructureOrClassType()) {
+    llvm::Type *VLSType = nullptr;
+    if (detectVLSCCEligibleStruct(Ty, ABIVLen, VLSType))
+      return ABIArgInfo::getDirect(VLSType);
+  }
+
   uint64_t NeededAlign = getContext().getTypeAlign(Ty);
   // Determine the number of GPRs needed to pass the current argument
   // according to the ABI. 2*XLen-aligned varargs are passed in "aligned"
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
index 3cb1fa0407d8a8..78e1ed37727894 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
@@ -67,3 +67,111 @@ void __attribute__((riscv_vls_cc(1024))) test_vls_least_element(__attribute__((v
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @test_vls_least_element_c23(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(1024)]] void test_vls_least_element_c23(__attribute__((vector_size(8))) int arg) {}
+
+
+struct st_i32x4{
+    __attribute__((vector_size(16))) int i32;
+};
+
+struct st_i32x4_arr1{
+    __attribute__((vector_size(16))) int i32[1];
+};
+
+struct st_i32x4_arr4{
+    __attribute__((vector_size(16))) int i32[4];
+};
+
+struct st_i32x4_arr8{
+    __attribute__((vector_size(16))) int i32[8];
+};
+
+
+struct st_i32x4x2{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+};
+
+struct st_i32x8x2{
+    __attribute__((vector_size(32))) int i32_1;
+    __attribute__((vector_size(32))) int i32_2;
+};
+
+struct st_i32x64x2{
+    __attribute__((vector_size(256))) int i32_1;
+    __attribute__((vector_size(256))) int i32_2;
+};
+
+struct st_i32x4x8{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+    __attribute__((vector_size(16))) int i32_3;
+    __attribute__((vector_size(16))) int i32_4;
+    __attribute__((vector_size(16))) int i32_5;
+    __attribute__((vector_size(16))) int i32_6;
+    __attribute__((vector_size(16))) int i32_7;
+    __attribute__((vector_size(16))) int i32_8;
+};
+
+struct st_i32x4x9{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+    __attribute__((vector_size(16))) int i32_3;
+    __attribute__((vector_size(16))) int i32_4;
+    __attribute__((vector_size(16))) int i32_5;
+    __attribute__((vector_size(16))) int i32_6;
+    __attribute__((vector_size(16))) int i32_7;
+    __attribute__((vector_size(16))) int i32_8;
+    __attribute__((vector_size(16))) int i32_9;
+};
+
+typedef int __attribute__((vector_size(256))) int32x64_t;
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_too_large(ptr noundef %0)
+void __attribute__((riscv_vls_cc)) test_too_large(int32x64_t arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_too_large_256(<vscale x 16 x i32> noundef %arg.coerce)
+void __attribute__((riscv_vls_cc(256))) test_too_large_256(int32x64_t arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4(<vscale x 2 x i32> %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4(struct st_i32x4 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_256(<vscale x 1 x i32> %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4_256(struct st_i32x4 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr1(<vscale x 2 x i32> %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4_arr1(struct st_i32x4_arr1 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr1_256(<vscale x 1 x i32> %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr1_256(struct st_i32x4_arr1 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr4(<vscale x 8 x i32> %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4_arr4(struct st_i32x4_arr4 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr4_256(<vscale x 4 x i32> %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr4_256(struct st_i32x4_arr4 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr8(<vscale x 16 x i32> %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4_arr8(struct st_i32x4_arr8 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4_arr8_256(<vscale x 8 x i32> %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr8_256(struct st_i32x4_arr8 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x2(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4x2(struct st_i32x4x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x2_256(target("riscv.vector.tuple", <vscale x 4 x i8>, 2) %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4x2_256(struct st_i32x4x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x8x2(target("riscv.vector.tuple", <vscale x 16 x i8>, 2) %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x8x2(struct st_i32x8x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x8x2_256(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x8x2_256(struct st_i32x8x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x64x2(ptr noundef %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x64x2(struct st_i32x64x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x64x2_256(ptr noundef %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x64x2_256(struct st_i32x64x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x8(target("riscv.vector.tuple", <vscale x 8 x i8>, 8) %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4x8(struct st_i32x4x8 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x8_256(target("riscv.vector.tuple", <vscale x 4 x i8>, 8) %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4x8_256(struct st_i32x4x8 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x9(ptr noundef %arg)
+void __attribute__((riscv_vls_cc)) test_st_i32x4x9(struct st_i32x4x9 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @test_st_i32x4x9_256(ptr noundef %arg)
+void __attribute__((riscv_vls_cc(256))) test_st_i32x4x9_256(struct st_i32x4x9 arg) {}
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
index 4265e129c2fdb8..6281b640c4df06 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
@@ -50,3 +50,111 @@ void test_vls_no_cc(__attribute__((vector_size(16))) int arg) {}
 
 // CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_vls_least_elementDv2_i(<vscale x 1 x i32> noundef %arg.coerce)
 [[riscv::vls_cc(1024)]] void test_vls_least_element(__attribute__((vector_size(8))) int arg) {}
+
+
+struct st_i32x4{
+    __attribute__((vector_size(16))) int i32;
+};
+
+struct st_i32x4_arr1{
+    __attribute__((vector_size(16))) int i32[1];
+};
+
+struct st_i32x4_arr4{
+    __attribute__((vector_size(16))) int i32[4];
+};
+
+struct st_i32x4_arr8{
+    __attribute__((vector_size(16))) int i32[8];
+};
+
+
+struct st_i32x4x2{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+};
+
+struct st_i32x8x2{
+    __attribute__((vector_size(32))) int i32_1;
+    __attribute__((vector_size(32))) int i32_2;
+};
+
+struct st_i32x64x2{
+    __attribute__((vector_size(256))) int i32_1;
+    __attribute__((vector_size(256))) int i32_2;
+};
+
+struct st_i32x4x8{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+    __attribute__((vector_size(16))) int i32_3;
+    __attribute__((vector_size(16))) int i32_4;
+    __attribute__((vector_size(16))) int i32_5;
+    __attribute__((vector_size(16))) int i32_6;
+    __attribute__((vector_size(16))) int i32_7;
+    __attribute__((vector_size(16))) int i32_8;
+};
+
+struct st_i32x4x9{
+    __attribute__((vector_size(16))) int i32_1;
+    __attribute__((vector_size(16))) int i32_2;
+    __attribute__((vector_size(16))) int i32_3;
+    __attribute__((vector_size(16))) int i32_4;
+    __attribute__((vector_size(16))) int i32_5;
+    __attribute__((vector_size(16))) int i32_6;
+    __attribute__((vector_size(16))) int i32_7;
+    __attribute__((vector_size(16))) int i32_8;
+    __attribute__((vector_size(16))) int i32_9;
+};
+
+typedef int __attribute__((vector_size(256))) int32x64_t;
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z14test_too_largeDv64_i(ptr noundef %0)
+[[riscv::vls_cc]] void test_too_large(int32x64_t arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z18test_too_large_256Dv64_i(<vscale x 16 x i32> noundef %arg.coerce)
+[[riscv::vls_cc(256)]] void test_too_large_256(int32x64_t arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z13test_st_i32x48st_i32x4(<vscale x 2 x i32> %arg)
+[[riscv::vls_cc]] void test_st_i32x4(struct st_i32x4 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z17test_st_i32x4_2568st_i32x4(<vscale x 1 x i32> %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4_256(struct st_i32x4 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z18test_st_i32x4_arr113st_i32x4_arr1(<vscale x 2 x i32> %arg)
+[[riscv::vls_cc]] void test_st_i32x4_arr1(struct st_i32x4_arr1 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_st_i32x4_arr1_25613st_i32x4_arr1(<vscale x 1 x i32> %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4_arr1_256(struct st_i32x4_arr1 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z18test_st_i32x4_arr413st_i32x4_arr4(<vscale x 8 x i32> %arg)
+[[riscv::vls_cc]] void test_st_i32x4_arr4(struct st_i32x4_arr4 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_st_i32x4_arr4_25613st_i32x4_arr4(<vscale x 4 x i32> %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4_arr4_256(struct st_i32x4_arr4 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z18test_st_i32x4_arr813st_i32x4_arr8(<vscale x 16 x i32> %arg)
+[[riscv::vls_cc]] void test_st_i32x4_arr8(struct st_i32x4_arr8 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z22test_st_i32x4_arr8_25613st_i32x4_arr8(<vscale x 8 x i32> %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4_arr8_256(struct st_i32x4_arr8 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z15test_st_i32x4x210st_i32x4x2(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
+[[riscv::vls_cc]] void test_st_i32x4x2(struct st_i32x4x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z19test_st_i32x4x2_25610st_i32x4x2(target("riscv.vector.tuple", <vscale x 4 x i8>, 2) %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4x2_256(struct st_i32x4x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z15test_st_i32x8x210st_i32x8x2(target("riscv.vector.tuple", <vscale x 16 x i8>, 2) %arg)
+[[riscv::vls_cc]] void test_st_i32x8x2(struct st_i32x8x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z19test_st_i32x8x2_25610st_i32x8x2(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x8x2_256(struct st_i32x8x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z16test_st_i32x64x211st_i32x64x2(ptr noundef %arg)
+[[riscv::vls_cc]] void test_st_i32x64x2(struct st_i32x64x2 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z20test_st_i32x64x2_25611st_i32x64x2(ptr noundef %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x64x2_256(struct st_i32x64x2 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z15test_st_i32x4x810st_i32x4x8(target("riscv.vector.tuple", <vscale x 8 x i8>, 8) %arg)
+[[riscv::vls_cc]] void test_st_i32x4x8(struct st_i32x4x8 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z19test_st_i32x4x8_25610st_i32x4x8(target("riscv.vector.tuple", <vscale x 4 x i8>, 8) %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4x8_256(struct st_i32x4x8 arg) {}
+
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z15test_st_i32x4x910st_i32x4x9(ptr noundef %arg)
+[[riscv::vls_cc]] void test_st_i32x4x9(struct st_i32x4x9 arg) {}
+// CHECK-LLVM: define dso_local riscv_vls_cc void @_Z19test_st_i32x4x9_25610st_i32x4x9(ptr noundef %arg)
+[[riscv::vls_cc(256)]] void test_st_i32x4x9_256(struct st_i32x4x9 arg) {}



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