[llvm-branch-commits] [clang] [CIR] Wire AMDGPU into the call-convention lowering pass (PR #220197)

via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Tue Sep 1 02:06:51 PDT 2026


https://github.com/skc7 created https://github.com/llvm/llvm-project/pull/220197

**Summary:** 
- Route the amdgpu triple to a new `CallConvTarget::AMDGPU` and drive the LLVM ABI library's AMDGPU classifier from CallConvLowering.

**Changes:**
- The X86-only classifier helpers are generalized to any target and thread the calling convention.
- Adds an `abi-lowering/amdgpu-scalars.cir` test for the supported cases.
- Opts `amdgcn-buffer-rsrc-type.hip` out of call-conv-lowering (TODO) until the bridge supports its direct-in-registers aggregate return.

Assisted by: Claude Opus 4.8

>From c1302daffefcefc3cc7874a63093bdcd1811c981 Mon Sep 17 00:00:00 2001
From: skc7 <Krishna.Sankisa at amd.com>
Date: Tue, 1 Sep 2026 14:31:15 +0530
Subject: [PATCH] [CIR] Wire AMDGPU into the call-convention lowering pass

---
 clang/include/clang/CIR/Dialect/Passes.h      |   2 +-
 clang/include/clang/CIR/Dialect/Passes.td     |   4 +-
 .../Transforms/CallConvLoweringPass.cpp       | 140 +++++++++++-------
 clang/lib/CIR/Lowering/CIRPasses.cpp          |   6 +-
 .../CodeGenHIP/amdgcn-buffer-rsrc-type.hip    |   8 +-
 .../abi-lowering/amdgpu-scalars.cir           | 105 +++++++++++++
 .../x86_64-lang-addrspace-nyi.cir             |   2 +-
 7 files changed, 204 insertions(+), 63 deletions(-)
 create mode 100644 clang/test/CIR/Transforms/abi-lowering/amdgpu-scalars.cir

diff --git a/clang/include/clang/CIR/Dialect/Passes.h b/clang/include/clang/CIR/Dialect/Passes.h
index 674f2180c27ab..796efff8e4d7c 100644
--- a/clang/include/clang/CIR/Dialect/Passes.h
+++ b/clang/include/clang/CIR/Dialect/Passes.h
@@ -20,7 +20,7 @@ namespace cir {
 /// The ABI target whose calling-convention rules drive CallConvLowering.
 /// None is the unset state used when the pass runs in classification-attr
 /// mode instead of selecting a target.
-enum class CallConvTarget { None, Test, X86_64 };
+enum class CallConvTarget { None, Test, X86_64, AMDGPU };
 } // namespace cir
 
 namespace clang {
diff --git a/clang/include/clang/CIR/Dialect/Passes.td b/clang/include/clang/CIR/Dialect/Passes.td
index b983cfe59112a..fd2ae1003d35c 100644
--- a/clang/include/clang/CIR/Dialect/Passes.td
+++ b/clang/include/clang/CIR/Dialect/Passes.td
@@ -246,7 +246,9 @@ def CallConvLowering : Pass<"cir-call-conv-lowering", "mlir::ModuleOp"> {
              clEnumValN(cir::CallConvTarget::Test, "test",
                         "MLIR test ABI target"),
              clEnumValN(cir::CallConvTarget::X86_64, "x86_64",
-                        "x86_64 System V")
+                        "x86_64 System V"),
+             clEnumValN(cir::CallConvTarget::AMDGPU, "amdgpu",
+                        "AMDGPU")
            )}]>,
     Option<"classificationAttr", "classification-attr", "std::string",
            /*default=*/"\"\"",
diff --git a/clang/lib/CIR/Dialect/Transforms/CallConvLoweringPass.cpp b/clang/lib/CIR/Dialect/Transforms/CallConvLoweringPass.cpp
index 11c2a66dba7b5..c1c69947d55c5 100644
--- a/clang/lib/CIR/Dialect/Transforms/CallConvLoweringPass.cpp
+++ b/clang/lib/CIR/Dialect/Transforms/CallConvLoweringPass.cpp
@@ -80,7 +80,7 @@ namespace {
 // bit-field access unit, a record holding an empty-for-ABI member that
 // occupies bytes or a zero-sized one off its own alignment, a union no member
 // of which spans its declared size, and a union with an empty-record member
-// are reported NYI by classifyX86_64Function so an unsupported signature
+// are reported NYI by classifyAbiSignature so an unsupported signature
 // fails the pass instead of being misclassified.
 //===----------------------------------------------------------------------===//
 
@@ -142,7 +142,7 @@ static bool reachesNamedBitFieldUnit(mlir::Type ty) {
 /// whose members are all themselves supported, or an array of a supported
 /// element type.  Also a `_Complex`, or a fixed-width vector, of a supported
 /// element type.  Everything else is reported NYI at the reject() choke point
-/// in classifyX86_64Function.
+/// in classifyAbiSignature.
 static bool isSupportedType(mlir::Type ty, const DataLayout &dl) {
   // A pointer is only handled in the default address space (null) or an
   // already-lowered target address space.  A LangAddressSpaceAttr must be
@@ -314,7 +314,7 @@ static mlir::Type abiTypeToCIR(const llvm::abi::Type *ty, MLIRContext *ctx) {
       .Default([](const llvm::abi::Type *) -> mlir::Type { return nullptr; });
 }
 
-/// Map a CIR type to an llvm::abi::Type.  classifyX86_64Function pre-filters
+/// Map a CIR type to an llvm::abi::Type.  classifyAbiSignature pre-filters
 /// the signature, so only the scalar and struct/array types handled here can
 /// reach this function.
 static const llvm::abi::Type *mapCIRType(mlir::Type type,
@@ -442,7 +442,7 @@ static const llvm::abi::Type *mapCIRType(mlir::Type type,
       })
       .Default([](mlir::Type) -> const llvm::abi::Type * {
         llvm_unreachable(
-            "mapCIRType: type not pre-filtered by classifyX86_64Function");
+            "mapCIRType: type not pre-filtered by classifyAbiSignature");
       });
 }
 
@@ -535,20 +535,31 @@ static llvm::abi::RequiredArgs requiredArgs(cir::FuncType fnTy) {
   return llvm::abi::RequiredArgs(fnTy.getNumInputs());
 }
 
-/// Classify an x86_64 SysV signature (return type + argument types) using the
-/// LLVM ABI library.  Shared by the cir.func path, the variadic-call path and
-/// the indirect-call path (the latter classifies from the callee function
+/// Map a cir.func calling convention to the llvm::CallingConv the ABI
+/// classifier keys on.  Only the AMDGPU kernel convention changes
+/// classification today; every other convention is classified as C.
+static llvm::CallingConv::ID abiCallingConv(cir::CallingConv cc) {
+  if (cc == cir::CallingConv::AMDGPUKernel)
+    return llvm::CallingConv::AMDGPU_KERNEL;
+  return llvm::CallingConv::C;
+}
+
+/// Classify a signature (return type + argument types) for \p targetInfo using
+/// the LLVM ABI library.  Shared by the cir.func path, the variadic-call path
+/// and the indirect-call path (the latter classifies from the callee function
 /// pointer's pointee FuncType).  \p required marks where the declared
 /// parameters in \p inputs end.  The classifier treats every argument past that
-/// point as passed through an ellipsis.  Returns std::nullopt and emits an NYI
-/// error via \p emitError if the signature uses a type the bridge does not
-/// handle yet.
-static std::optional<FunctionClassification> classifyX86_64Signature(
-    mlir::Type retCIR, mlir::TypeRange inputs, llvm::abi::RequiredArgs required,
-    MLIRContext *ctx, const DataLayout &dl,
-    mlir::abi::ABITypeMapper &typeMapper,
-    const llvm::abi::TargetInfo &targetInfo, ModuleOp modOp,
-    llvm::function_ref<mlir::InFlightDiagnostic()> emitError) {
+/// point as passed through an ellipsis.  \p callConv selects the ABI convention
+/// (e.g. AMDGPU_KERNEL), which some targets classify differently.  Returns
+/// std::nullopt and emits an NYI error via \p emitError if the signature uses a
+/// type the bridge does not handle yet.
+static std::optional<FunctionClassification>
+classifyAbiSignature(mlir::Type retCIR, mlir::TypeRange inputs,
+                     llvm::abi::RequiredArgs required, MLIRContext *ctx,
+                     const DataLayout &dl, mlir::abi::ABITypeMapper &typeMapper,
+                     const llvm::abi::TargetInfo &targetInfo,
+                     llvm::CallingConv::ID callConv, ModuleOp modOp,
+                     llvm::function_ref<mlir::InFlightDiagnostic()> emitError) {
   assert(retCIR && "signature return type must be non-null");
   assert((!required.allowsOptionalArgs() ||
           required.getNumRequiredArgs() <= inputs.size()) &&
@@ -558,9 +569,8 @@ static std::optional<FunctionClassification> classifyX86_64Signature(
   auto reject = [&](mlir::Type t) -> bool {
     if (isSupportedType(t, dl))
       return false;
-    emitError()
-        << "x86_64 calling-convention lowering not yet implemented for type "
-        << t;
+    emitError() << "calling-convention lowering not yet implemented for type "
+                << t;
     return true;
   };
   if (!voidRet && reject(retCIR))
@@ -576,15 +586,15 @@ static std::optional<FunctionClassification> classifyX86_64Signature(
   for (mlir::Type a : inputs)
     argAbi.push_back(mapCIRType(a, typeMapper, dl, modOp));
 
-  std::unique_ptr<llvm::abi::FunctionInfo> fi = llvm::abi::FunctionInfo::create(
-      llvm::CallingConv::C, retAbi, argAbi, required);
+  std::unique_ptr<llvm::abi::FunctionInfo> fi =
+      llvm::abi::FunctionInfo::create(callConv, retAbi, argAbi, required);
   targetInfo.computeInfo(*fi);
 
   // convertABIArgInfo returns nullopt when the classifier picks a coercion this
   // bridge cannot represent.
   auto nyiCoercion = [&](mlir::Type t) {
-    emitError() << "x86_64 calling-convention lowering not yet "
-                   "implemented for the ABI coercion of type "
+    emitError() << "calling-convention lowering not yet implemented for the "
+                   "ABI coercion of type "
                 << t;
   };
 
@@ -636,19 +646,19 @@ static llvm::abi::X86AVXABILevel funcAvxLevel(cir::FuncOp func,
   return avx ? std::max(base, llvm::abi::X86AVXABILevel::AVX) : base;
 }
 
-/// Classify a cir.func for x86_64 SysV using the LLVM ABI library.  Returns
+/// Classify a cir.func for \p targetInfo using the LLVM ABI library.  Returns
 /// std::nullopt and emits an NYI error if the signature uses a type the bridge
 /// does not handle yet.
 static std::optional<FunctionClassification>
-classifyX86_64Function(cir::FuncOp func, const DataLayout &dl,
-                       mlir::abi::ABITypeMapper &typeMapper,
-                       const llvm::abi::TargetInfo &targetInfo,
-                       ModuleOp modOp) {
+classifyAbiFunction(cir::FuncOp func, const DataLayout &dl,
+                    mlir::abi::ABITypeMapper &typeMapper,
+                    const llvm::abi::TargetInfo &targetInfo, ModuleOp modOp) {
   cir::FuncType fnTy = func.getFunctionType();
-  return classifyX86_64Signature(fnTy.getReturnType(), fnTy.getInputs(),
-                                 requiredArgs(fnTy), func->getContext(), dl,
-                                 typeMapper, targetInfo, modOp,
-                                 [&]() { return func.emitOpError(); });
+  return classifyAbiSignature(fnTy.getReturnType(), fnTy.getInputs(),
+                              requiredArgs(fnTy), func->getContext(), dl,
+                              typeMapper, targetInfo,
+                              abiCallingConv(func.getCallingConv()), modOp,
+                              [&]() { return func.emitOpError(); });
 }
 
 /// Classify a call that passes arguments through an ellipsis.  The callee's
@@ -658,17 +668,19 @@ classifyX86_64Function(cir::FuncOp func, const DataLayout &dl,
 /// small struct is passed in registers early in the list and in memory once
 /// the integer registers are gone.  Classifying from the call's operands
 /// rather than the callee's signature is what makes that accounting right.
-static std::optional<FunctionClassification> classifyX86_64VariadicCall(
-    cir::CIRCallOpInterface call, cir::FuncType calleeTy, const DataLayout &dl,
-    mlir::abi::ABITypeMapper &typeMapper,
-    const llvm::abi::TargetInfo &targetInfo, ModuleOp modOp) {
+static std::optional<FunctionClassification>
+classifyAbiVariadicCall(cir::CIRCallOpInterface call, cir::FuncType calleeTy,
+                        const DataLayout &dl,
+                        mlir::abi::ABITypeMapper &typeMapper,
+                        const llvm::abi::TargetInfo &targetInfo,
+                        llvm::CallingConv::ID callConv, ModuleOp modOp) {
   assert(calleeTy.isVarArg() &&
          "only a variadic callee can take more operands than it declares");
   Operation *op = call.getOperation();
-  return classifyX86_64Signature(
+  return classifyAbiSignature(
       calleeTy.getReturnType(), call.getArgOperands().getTypes(),
       requiredArgs(calleeTy), op->getContext(), dl, typeMapper, targetInfo,
-      modOp, [&]() { return op->emitOpError(); });
+      callConv, modOp, [&]() { return op->emitOpError(); });
 }
 
 #ifndef NDEBUG
@@ -810,10 +822,18 @@ void CallConvLoweringPass::runOnOperation() {
   static constexpr unsigned numAvxLevels =
       static_cast<unsigned>(llvm::abi::X86AVXABILevel::Last) + 1;
   bool isX86 = target == cir::CallConvTarget::X86_64;
-  std::optional<mlir::abi::ABITypeMapper> x86TypeMapper;
+  bool isAMDGPU = target == cir::CallConvTarget::AMDGPU;
+  // The x86_64 and AMDGPU drivers classify with the LLVM ABI library and share
+  // the type mapper; the test and classification-attr drivers do neither.
+  bool useAbiClassifier = isX86 || isAMDGPU;
+  std::optional<mlir::abi::ABITypeMapper> abiTypeMapper;
   std::array<std::unique_ptr<llvm::abi::TargetInfo>, numAvxLevels> x86Targets;
-  if (isX86)
-    x86TypeMapper.emplace(dl);
+  std::unique_ptr<llvm::abi::TargetInfo> amdgpuTarget;
+  if (useAbiClassifier)
+    abiTypeMapper.emplace(dl);
+  if (isAMDGPU)
+    amdgpuTarget =
+        llvm::abi::createAMDGPUTargetInfo(abiTypeMapper->getTypeBuilder());
   auto x86TargetFor =
       [&](llvm::abi::X86AVXABILevel level) -> const llvm::abi::TargetInfo & {
     assert(static_cast<unsigned>(level) < numAvxLevels &&
@@ -822,7 +842,7 @@ void CallConvLoweringPass::runOnOperation() {
         x86Targets[static_cast<unsigned>(level)];
     if (!slot)
       slot = llvm::abi::createX86_64TargetInfo(
-          x86TypeMapper->getTypeBuilder(), level,
+          abiTypeMapper->getTypeBuilder(), level,
           /*Has64BitPointers=*/true, x86AbiCompat);
     return *slot;
   };
@@ -832,6 +852,13 @@ void CallConvLoweringPass::runOnOperation() {
       return baseAvxLevel;
     return funcAvxLevel(func, baseAvxLevel);
   };
+  // The classifier to use for a function/call reached from \p func.  AMDGPU has
+  // a single classifier; x86_64 picks the one matching func's AVX level.
+  auto targetInfoFor = [&](cir::FuncOp func) -> const llvm::abi::TargetInfo & {
+    if (isAMDGPU)
+      return *amdgpuTarget;
+    return x86TargetFor(avxLevelFor(func));
+  };
 
   // Classify every cir.func up front.  No IR mutation happens here, so
   // later walks can consult any function's classification regardless of
@@ -840,9 +867,9 @@ void CallConvLoweringPass::runOnOperation() {
   bool anyFailed = false;
   moduleOp.walk([&](cir::FuncOp f) {
     std::optional<FunctionClassification> fc;
-    if (isX86)
-      fc = classifyX86_64Function(f, dl, *x86TypeMapper,
-                                  x86TargetFor(avxLevelFor(f)), moduleOp);
+    if (useAbiClassifier)
+      fc = classifyAbiFunction(f, dl, *abiTypeMapper, targetInfoFor(f),
+                               moduleOp);
     else
       fc = classifyFunction(f, dl, target, classificationAttr);
     if (!fc) {
@@ -879,11 +906,12 @@ void CallConvLoweringPass::runOnOperation() {
       return;
     callers[callee].push_back(op);
 
-    // Only the x86_64 driver classifies per call site.  Under the other
+    // Only the ABI-library drivers classify per call site.  Under the other
     // drivers the classification comes from a fixed per-function source, so
     // such a call stays short a classification and rewriteCallSite reports it.
     cir::FuncType calleeTy = callee.getFunctionType();
-    if (!isX86 || call.getNumArgOperands() <= calleeTy.getNumInputs())
+    if (!useAbiClassifier ||
+        call.getNumArgOperands() <= calleeTy.getNumInputs())
       return;
     // A callee declared without a prototype also takes more operands than it
     // declares, and the verifier allows it.  Those extra arguments are named
@@ -900,9 +928,9 @@ void CallConvLoweringPass::runOnOperation() {
     // Classic instead arranges every call site from the caller and reports a
     // caller whose level disagrees with its callee in checkFunctionCallABI,
     // which has no equivalent here yet.
-    std::optional<FunctionClassification> fc =
-        classifyX86_64VariadicCall(call, calleeTy, dl, *x86TypeMapper,
-                                   x86TargetFor(avxLevelFor(callee)), moduleOp);
+    std::optional<FunctionClassification> fc = classifyAbiVariadicCall(
+        call, calleeTy, dl, *abiTypeMapper, targetInfoFor(callee),
+        abiCallingConv(callee.getCallingConv()), moduleOp);
     if (!fc) {
       anyFailed = true;
       return;
@@ -995,13 +1023,13 @@ void CallConvLoweringPass::runOnOperation() {
         [&](mlir::TypeRange argTypes) -> std::optional<FunctionClassification> {
       // A callee resolved at run time carries no features of its own, so the
       // level comes from the function containing the call, which is the
-      // declaration classic arranges every call site from.
-      if (isX86)
-        return classifyX86_64Signature(
+      // declaration classic arranges every call site from.  An indirect callee
+      // is an ordinary function pointer, so it uses the C convention.
+      if (useAbiClassifier)
+        return classifyAbiSignature(
             funcTy.getReturnType(), argTypes, requiredArgs(funcTy), ctx, dl,
-            *x86TypeMapper,
-            x86TargetFor(avxLevelFor(c->getParentOfType<cir::FuncOp>())),
-            moduleOp, [&]() { return c->emitOpError(); });
+            *abiTypeMapper, targetInfoFor(c->getParentOfType<cir::FuncOp>()),
+            llvm::CallingConv::C, moduleOp, [&]() { return c->emitOpError(); });
       return withReturnVoidness(
           mlir::abi::test::classify(argTypes, funcTy.getReturnType(), dl),
           funcTy.getReturnType());
diff --git a/clang/lib/CIR/Lowering/CIRPasses.cpp b/clang/lib/CIR/Lowering/CIRPasses.cpp
index 64d82dd4e7301..6b86ab69fd614 100644
--- a/clang/lib/CIR/Lowering/CIRPasses.cpp
+++ b/clang/lib/CIR/Lowering/CIRPasses.cpp
@@ -26,6 +26,8 @@ namespace cir {
 static CallConvTarget getCallConvTarget(const llvm::Triple &triple) {
   if (triple.getArch() == llvm::Triple::x86_64)
     return CallConvTarget::X86_64;
+  if (triple.isAMDGPU())
+    return CallConvTarget::AMDGPU;
   return CallConvTarget::None;
 }
 
@@ -115,8 +117,8 @@ runCIRToCIRPasses(mlir::ModuleOp theModule, mlir::MLIRContext &mlirContext,
   if (enableCallConvLowering) {
     // CallConvLowering rewrites signatures and call sites using the classifier,
     // so it must run after CXXABILowering has lowered C++ ABI types to plain
-    // records the classifier can handle.  Only the x86_64 System V classifier
-    // is implemented; other targets are left unchanged.
+    // records the classifier can handle.  Only the x86_64 System V and AMDGPU
+    // classifiers are implemented; other targets are left unchanged.
     const clang::TargetInfo &targetInfo = astContext.getTargetInfo();
     CallConvTarget target = getCallConvTarget(targetInfo.getTriple());
     if (target != CallConvTarget::None)
diff --git a/clang/test/CIR/CodeGenHIP/amdgcn-buffer-rsrc-type.hip b/clang/test/CIR/CodeGenHIP/amdgcn-buffer-rsrc-type.hip
index e03fa4db5c20d..0045a731c579f 100644
--- a/clang/test/CIR/CodeGenHIP/amdgcn-buffer-rsrc-type.hip
+++ b/clang/test/CIR/CodeGenHIP/amdgcn-buffer-rsrc-type.hip
@@ -1,12 +1,16 @@
 #include "../CodeGenCUDA/Inputs/cuda.h"
 
 // REQUIRES: amdgpu-registered-target
+
+// TODO(cir): drop -fno-clangir-call-conv-lowering once CallConvLowering
+// supports the AMDGPU direct-in-registers aggregate return of a buffer
+// resource struct.
 // RUN: %clang_cc1 -triple amdgpu11.00-amd-amdhsa -x hip -std=c++11 -fclangir \
-// RUN: -fcuda-is-device -emit-cir %s -o %t.cir
+// RUN: -fcuda-is-device -fno-clangir-call-conv-lowering -emit-cir %s -o %t.cir
 // RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
 
 // RUN: %clang_cc1 -triple amdgpu11.00-amd-amdhsa -x hip -std=c++11 -fclangir \
-// RUN: -fcuda-is-device -emit-llvm %s -o %t-cir.ll
+// RUN: -fcuda-is-device -fno-clangir-call-conv-lowering -emit-llvm %s -o %t-cir.ll
 // RUN: FileCheck --check-prefix=LLVM --input-file=%t-cir.ll %s
 
 // RUN: %clang_cc1 -triple amdgpu11.00-amd-amdhsa -x hip -std=c++11 \
diff --git a/clang/test/CIR/Transforms/abi-lowering/amdgpu-scalars.cir b/clang/test/CIR/Transforms/abi-lowering/amdgpu-scalars.cir
new file mode 100644
index 0000000000000..5b9049e119757
--- /dev/null
+++ b/clang/test/CIR/Transforms/abi-lowering/amdgpu-scalars.cir
@@ -0,0 +1,105 @@
+// RUN: cir-opt %s -cir-call-conv-lowering=target=amdgpu | FileCheck %s
+
+!s8i = !cir.int<s, 8>
+!s16i = !cir.int<s, 16>
+!u16i = !cir.int<u, 16>
+!s32i = !cir.int<s, 32>
+!s64i = !cir.int<s, 64>
+
+!rec_E0 = !cir.struct<"E0" {}>
+!rec_Pair16 = !cir.struct<"Pair16" {data !s16i, data !s16i}>
+
+module attributes {
+  dlti.dl_spec = #dlti.dl_spec<
+    #dlti.dl_entry<i1, dense<8>: vector<2xi64>>,
+    #dlti.dl_entry<i8, dense<8>: vector<2xi64>>,
+    #dlti.dl_entry<i16, dense<16>: vector<2xi64>>,
+    #dlti.dl_entry<i32, dense<32>: vector<2xi64>>,
+    #dlti.dl_entry<i64, dense<64>: vector<2xi64>>>
+} {
+
+  // Register-sized integers are Direct: signature and call sites unchanged.
+  cir.func @passthrough(%arg0: !s32i, %arg1: !s64i) -> !s32i {
+    cir.return %arg0 : !s32i
+  }
+
+  // CHECK: cir.func{{.*}} @passthrough(%arg0: !s32i, %arg1: !s64i) -> !s32i
+  // CHECK-NEXT: cir.return %arg0 : !s32i
+
+  // Floating-point scalars are Direct.
+  cir.func @floats(%arg0: !cir.float, %arg1: !cir.double) -> !cir.double {
+    cir.return %arg1 : !cir.double
+  }
+
+  // CHECK: cir.func{{.*}} @floats(%arg0: !cir.float, %arg1: !cir.double) -> !cir.double
+
+  // Pointers are Direct.
+  cir.func @take_ptr(%arg0: !cir.ptr<!s32i>) -> !cir.ptr<!s32i> {
+    cir.return %arg0 : !cir.ptr<!s32i>
+  }
+
+  // CHECK: cir.func{{.*}} @take_ptr(%arg0: !cir.ptr<!s32i>) -> !cir.ptr<!s32i>
+
+  // Signed sub-register integer is sign-extended.
+  cir.func @take_s8(%arg0: !s8i) {
+    cir.return
+  }
+
+  // CHECK: cir.func{{.*}} @take_s8(%arg0: !s8i {llvm.signext})
+
+  // Unsigned sub-register integer is zero-extended.
+  cir.func @take_u16(%arg0: !u16i) {
+    cir.return
+  }
+
+  // CHECK: cir.func{{.*}} @take_u16(%arg0: !u16i {llvm.zeroext})
+
+  // bool is zero-extended.
+  cir.func @take_bool(%arg0: !cir.bool) {
+    cir.return
+  }
+
+  // CHECK: cir.func{{.*}} @take_bool(%arg0: !cir.bool {llvm.zeroext})
+
+  // Call site picks up the same extension attribute on the operand.
+  cir.func @call_s8(%arg0: !s8i) {
+    cir.call @take_s8(%arg0) : (!s8i) -> ()
+    cir.return
+  }
+
+  // CHECK: cir.call @take_s8(%arg0) : (!s8i {llvm.signext}) -> ()
+
+  // A sub-register integer return is also extended, not just arguments.
+  cir.func @ret_s8() -> !s8i {
+    %0 = cir.const #cir.int<0> : !s8i
+    cir.return %0 : !s8i
+  }
+
+  // CHECK: cir.func{{.*}} @ret_s8() -> (!s8i {llvm.signext})
+
+  // A zero-field record classifies as Ignore: the empty argument is dropped
+  // and the real argument shifts down to the first slot.
+  cir.func @take_empty(%arg0: !rec_E0, %arg1: !s32i) -> !s32i {
+    cir.return %arg1 : !s32i
+  }
+
+  // CHECK: cir.func{{.*}} @take_empty(%arg0: !s32i) -> !s32i
+  // CHECK-NEXT: cir.return %arg0 : !s32i
+
+  // A small aggregate (<= 32 bits) is packed into a single i32 register.
+  cir.func @takes_small(%arg0: !rec_Pair16) {
+    %0 = cir.alloca "p" align(4) : !cir.ptr<!rec_Pair16>
+    cir.store %arg0, %0 : !rec_Pair16, !cir.ptr<!rec_Pair16>
+    cir.return
+  }
+
+  // CHECK: cir.func{{.*}} @takes_small(%{{.*}}: !u32i)
+
+  // A kernel scalar argument stays Direct: the AMDGPU_KERNEL convention is
+  // routed to the kernel classifier and the signature is unchanged.
+  cir.func @kernel_scalar(%arg0: !s32i) cc(amdgpu_kernel) {
+    cir.return
+  }
+
+  // CHECK: cir.func{{.*}} @kernel_scalar(%arg0: !s32i){{.*}}cc(amdgpu_kernel)
+}
diff --git a/clang/test/CIR/Transforms/abi-lowering/x86_64-lang-addrspace-nyi.cir b/clang/test/CIR/Transforms/abi-lowering/x86_64-lang-addrspace-nyi.cir
index a8350b421757d..285df67e53c83 100644
--- a/clang/test/CIR/Transforms/abi-lowering/x86_64-lang-addrspace-nyi.cir
+++ b/clang/test/CIR/Transforms/abi-lowering/x86_64-lang-addrspace-nyi.cir
@@ -15,4 +15,4 @@ module attributes {
 
 }
 
-// CHECK: op x86_64 calling-convention lowering not yet implemented for type
+// CHECK: op calling-convention lowering not yet implemented for type



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