[llvm-branch-commits] [clang] [Clang][AMDGPU] Add ``amdgcn_av("none")`` attribute for atomic expressions (PR #199622)

via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Tue May 26 00:52:59 PDT 2026


llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Sameer Sahasrabuddhe (ssahasra)

<details>
<summary>Changes</summary>

Add a statement attribute that suppresses MakeAvailable/MakeVisible cache operations on AMDGPU atomic instructions while preserving memory ordering (waits).

The attribute takes a string argument specifying the mode. Currently "none" is the only supported mode. The resulting atomic or fence instruction carries !mmra !{!"amdgcn-av", !"none"} metadata.

Assisted-By: Claude Opus 4.6

---

Patch is 28.20 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/199622.diff


13 Files Affected:

- (modified) clang/include/clang/Basic/Attr.td (+6) 
- (modified) clang/include/clang/Basic/AttrDocs.td (+23) 
- (modified) clang/include/clang/Basic/DiagnosticGroups.td (+2) 
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+4) 
- (modified) clang/lib/CodeGen/CGAtomic.cpp (+8-1) 
- (modified) clang/lib/CodeGen/CGBuiltin.cpp (+42-26) 
- (modified) clang/lib/CodeGen/CGStmt.cpp (+5) 
- (modified) clang/lib/CodeGen/CodeGenFunction.h (+4) 
- (modified) clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp (+1) 
- (modified) clang/lib/CodeGen/Targets/AMDGPU.cpp (+6) 
- (modified) clang/lib/Sema/SemaStmtAttr.cpp (+57) 
- (added) clang/test/CodeGen/AMDGPU/amdgcn-av-non-atomic.cpp (+43) 
- (added) clang/test/CodeGen/AMDGPU/amdgcn-av-none-attr.cpp (+131) 


``````````diff
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 70b5773f95b08..b11b3ed51efc4 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -2520,6 +2520,12 @@ def AMDGPUMaxNumWorkGroups : InheritableAttr {
   let Subjects = SubjectList<[Function], ErrorDiag, "kernel functions">;
 }
 
+def AMDGCNAV : StmtAttr, TargetSpecificAttr<TargetAMDGPU> {
+  let Spellings = [Clang<"amdgcn_av">];
+  let Args = [StringArgument<"Mode">];
+  let Documentation = [AMDGCNAVDocs];
+}
+
 def BPFPreserveAccessIndex : InheritableAttr,
                              TargetSpecificAttr<TargetBPF>  {
   let Spellings = [Clang<"preserve_access_index">];
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 87b9053be7cb6..f2835bffd4bc5 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -3543,6 +3543,29 @@ An error will be given if:
   }];
 }
 
+def AMDGCNAVDocs : Documentation {
+  let Category = DocCatAMDGPUAttributes;
+  let Content = [{
+This attribute controls MakeAvailable and MakeVisible cache operations on
+AMDGPU synchronization operations. It takes a string argument specifying the
+mode.
+
+When placed on a statement containing a C/C++ atomic builtin call, the
+resulting atomic or fence instruction will carry ``!mmra !{!"amdgcn-av",
+!"<mode>"}`` metadata.
+
+The supported modes are:
+
+- ``"none"``: Skip cache writeback (on release) and cache invalidation (on
+  acquire), while preserving memory ordering (waits).
+
+.. code-block:: c++
+
+  [[clang::amdgcn_av("none")]] __atomic_thread_fence(__ATOMIC_SEQ_CST);
+  [[clang::amdgcn_av("none")]] __atomic_fetch_add(ptr, 1, __ATOMIC_ACQ_REL);
+  }];
+}
+
 def DocCatCallingConvs : DocumentationCategory<"Calling Conventions"> {
   let Content = [{
 Clang supports several different calling conventions, depending on the target
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 8031f99419bdc..51787935e1280 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -1968,3 +1968,5 @@ def ExperimentalOption : DiagGroup<"experimental-option">;
 
 // Warnings about unguarded usages of AMDGPU target specific constructs
 def UnguardedBuiltinUsageAMDGPU : DiagGroup<"amdgpu-unguarded-builtin-usage">;
+
+def AMDGCNAVNonAtomic : DiagGroup<"amdgcn-av-non-atomic">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index dbe6cb2c3a41c..c91b5774d0272 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -14232,6 +14232,10 @@ def note_amdgcn_unguarded_builtin_silence
 
 def err_amdgcn_coop_atomic_invalid_as : Error<"cooperative atomic requires a global or generic pointer">;
 
+def warn_amdgcn_av_requires_atomic : Warning<
+  "%0 attribute only applies to atomic operations">,
+  InGroup<AMDGCNAVNonAtomic>;
+
 def err_amdgcn_dmask_has_too_many_bits_set
     : Error<"dmask argument cannot have more bits set than there are elements "
             "in return type">;
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index 270965b109943..92ee116ca8dc0 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -632,6 +632,7 @@ static void EmitAtomicOp(CodeGenFunction &CGF, AtomicExpr *E, Address Dest,
     llvm::LoadInst *Load = CGF.Builder.CreateLoad(Ptr);
     Load->setAtomic(Order, Scope);
     Load->setVolatile(E->isVolatile());
+    CGF.getTargetHooks().setTargetAtomicMetadata(CGF, *Load, E);
     CGF.maybeAttachRangeForLoad(Load, E->getValueType(), E->getExprLoc());
     auto *I = CGF.Builder.CreateStore(Load, Dest);
     CGF.addInstToCurrentSourceAtom(I, Load);
@@ -649,6 +650,7 @@ static void EmitAtomicOp(CodeGenFunction &CGF, AtomicExpr *E, Address Dest,
     llvm::StoreInst *Store = CGF.Builder.CreateStore(LoadVal1, Ptr);
     Store->setAtomic(Order, Scope);
     Store->setVolatile(E->isVolatile());
+    CGF.getTargetHooks().setTargetAtomicMetadata(CGF, *Store, E);
     CGF.addInstToCurrentSourceAtom(Store, LoadVal1);
     return;
   }
@@ -795,6 +797,7 @@ static void EmitAtomicOp(CodeGenFunction &CGF, AtomicExpr *E, Address Dest,
         CGF.Builder.CreateStore(CGF.Builder.getInt8(0), Ptr);
     Store->setAtomic(Order, Scope);
     Store->setVolatile(E->isVolatile());
+    CGF.getTargetHooks().setTargetAtomicMetadata(CGF, *Store, E);
     CGF.addInstToCurrentSourceAtom(Store, nullptr);
     return;
   }
@@ -1586,6 +1589,7 @@ llvm::Value *AtomicInfo::EmitAtomicLoadOp(llvm::AtomicOrdering AO,
     Addr = castToAtomicIntPointer(Addr);
   llvm::LoadInst *Load = CGF.Builder.CreateLoad(Addr, "atomic-load");
   Load->setAtomic(AO);
+  CGF.getTargetHooks().setTargetAtomicMetadata(CGF, *Load);
 
   // Other decoration.
   if (IsVolatile)
@@ -1753,6 +1757,7 @@ std::pair<llvm::Value *, llvm::Value *> AtomicInfo::EmitAtomicCompareExchangeOp(
   // Other decoration.
   Inst->setVolatile(LVal.isVolatileQualified());
   Inst->setWeak(IsWeak);
+  CGF.getTargetHooks().setTargetAtomicMetadata(CGF, *Inst);
 
   // Okay, turn that back into the original value type.
   auto *PreviousVal = CGF.Builder.CreateExtractValue(Inst, /*Idxs=*/0);
@@ -2108,8 +2113,10 @@ void CodeGenFunction::EmitAtomicStore(RValue rvalue, LValue dest,
     else if (AO == llvm::AtomicOrdering::AcquireRelease)
       AO = llvm::AtomicOrdering::Release;
     // Initializations don't need to be atomic.
-    if (!isInit)
+    if (!isInit) {
       store->setAtomic(AO);
+      getTargetHooks().setTargetAtomicMetadata(*this, *store);
+    }
 
     // Other decoration.
     if (IsVolatile)
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index b1d727cb5e0ad..4e36d4fe1dc32 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -5367,24 +5367,28 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     Value *Order = EmitScalarExpr(E->getArg(0));
     if (isa<llvm::ConstantInt>(Order)) {
       int ord = cast<llvm::ConstantInt>(Order)->getZExtValue();
+      llvm::FenceInst *Fence = nullptr;
       switch (ord) {
       case 0:  // memory_order_relaxed
       default: // invalid order
         break;
       case 1:  // memory_order_consume
       case 2:  // memory_order_acquire
-        Builder.CreateFence(llvm::AtomicOrdering::Acquire, SSID);
+        Fence = Builder.CreateFence(llvm::AtomicOrdering::Acquire, SSID);
         break;
       case 3:  // memory_order_release
-        Builder.CreateFence(llvm::AtomicOrdering::Release, SSID);
+        Fence = Builder.CreateFence(llvm::AtomicOrdering::Release, SSID);
         break;
       case 4:  // memory_order_acq_rel
-        Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease, SSID);
+        Fence = Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease, SSID);
         break;
       case 5:  // memory_order_seq_cst
-        Builder.CreateFence(llvm::AtomicOrdering::SequentiallyConsistent, SSID);
+        Fence = Builder.CreateFence(
+            llvm::AtomicOrdering::SequentiallyConsistent, SSID);
         break;
       }
+      if (Fence)
+        getTargetHooks().setTargetAtomicMetadata(*this, *Fence);
       return RValue::get(nullptr);
     }
 
@@ -5399,23 +5403,29 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     llvm::SwitchInst *SI = Builder.CreateSwitch(Order, ContBB);
 
     Builder.SetInsertPoint(AcquireBB);
-    Builder.CreateFence(llvm::AtomicOrdering::Acquire, SSID);
+    getTargetHooks().setTargetAtomicMetadata(
+        *this, *Builder.CreateFence(llvm::AtomicOrdering::Acquire, SSID));
     Builder.CreateBr(ContBB);
     SI->addCase(Builder.getInt32(1), AcquireBB);
     SI->addCase(Builder.getInt32(2), AcquireBB);
 
     Builder.SetInsertPoint(ReleaseBB);
-    Builder.CreateFence(llvm::AtomicOrdering::Release, SSID);
+    getTargetHooks().setTargetAtomicMetadata(
+        *this, *Builder.CreateFence(llvm::AtomicOrdering::Release, SSID));
     Builder.CreateBr(ContBB);
     SI->addCase(Builder.getInt32(3), ReleaseBB);
 
     Builder.SetInsertPoint(AcqRelBB);
-    Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease, SSID);
+    getTargetHooks().setTargetAtomicMetadata(
+        *this,
+        *Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease, SSID));
     Builder.CreateBr(ContBB);
     SI->addCase(Builder.getInt32(4), AcqRelBB);
 
     Builder.SetInsertPoint(SeqCstBB);
-    Builder.CreateFence(llvm::AtomicOrdering::SequentiallyConsistent, SSID);
+    getTargetHooks().setTargetAtomicMetadata(
+        *this, *Builder.CreateFence(
+                   llvm::AtomicOrdering::SequentiallyConsistent, SSID));
     Builder.CreateBr(ContBB);
     SI->addCase(Builder.getInt32(5), SeqCstBB);
 
@@ -5433,40 +5443,43 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
       SyncScope SS = ScopeModel->isValid(Scp->getZExtValue())
                          ? ScopeModel->map(Scp->getZExtValue())
                          : ScopeModel->map(ScopeModel->getFallBackValue());
+      llvm::FenceInst *Fence = nullptr;
       switch (Ord->getZExtValue()) {
       case 0:  // memory_order_relaxed
       default: // invalid order
         break;
       case 1: // memory_order_consume
       case 2: // memory_order_acquire
-        Builder.CreateFence(
+        Fence = Builder.CreateFence(
             llvm::AtomicOrdering::Acquire,
             getTargetHooks().getLLVMSyncScopeID(getLangOpts(), SS,
                                                 llvm::AtomicOrdering::Acquire,
                                                 getLLVMContext()));
         break;
       case 3: // memory_order_release
-        Builder.CreateFence(
+        Fence = Builder.CreateFence(
             llvm::AtomicOrdering::Release,
             getTargetHooks().getLLVMSyncScopeID(getLangOpts(), SS,
                                                 llvm::AtomicOrdering::Release,
                                                 getLLVMContext()));
         break;
       case 4: // memory_order_acq_rel
-        Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease,
-                            getTargetHooks().getLLVMSyncScopeID(
-                                getLangOpts(), SS,
-                                llvm::AtomicOrdering::AcquireRelease,
-                                getLLVMContext()));
+        Fence = Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease,
+                                    getTargetHooks().getLLVMSyncScopeID(
+                                        getLangOpts(), SS,
+                                        llvm::AtomicOrdering::AcquireRelease,
+                                        getLLVMContext()));
         break;
       case 5: // memory_order_seq_cst
-        Builder.CreateFence(llvm::AtomicOrdering::SequentiallyConsistent,
-                            getTargetHooks().getLLVMSyncScopeID(
-                                getLangOpts(), SS,
-                                llvm::AtomicOrdering::SequentiallyConsistent,
-                                getLLVMContext()));
+        Fence = Builder.CreateFence(
+            llvm::AtomicOrdering::SequentiallyConsistent,
+            getTargetHooks().getLLVMSyncScopeID(
+                getLangOpts(), SS, llvm::AtomicOrdering::SequentiallyConsistent,
+                getLLVMContext()));
         break;
       }
+      if (Fence)
+        getTargetHooks().setTargetAtomicMetadata(*this, *Fence);
       return RValue::get(nullptr);
     }
 
@@ -5525,9 +5538,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
         SyncScope SS = ScopeModel->isValid(Scp->getZExtValue())
                            ? ScopeModel->map(Scp->getZExtValue())
                            : ScopeModel->map(ScopeModel->getFallBackValue());
-        Builder.CreateFence(Ordering,
-                            getTargetHooks().getLLVMSyncScopeID(
-                                getLangOpts(), SS, Ordering, getLLVMContext()));
+        llvm::FenceInst *Fence = Builder.CreateFence(
+            Ordering, getTargetHooks().getLLVMSyncScopeID(
+                          getLangOpts(), SS, Ordering, getLLVMContext()));
+        getTargetHooks().setTargetAtomicMetadata(*this, *Fence);
         Builder.CreateBr(ContBB);
       } else {
         llvm::DenseMap<unsigned, llvm::BasicBlock *> BBs;
@@ -5541,9 +5555,11 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
           SI->addCase(Builder.getInt32(Scp), B);
 
           Builder.SetInsertPoint(B);
-          Builder.CreateFence(Ordering, getTargetHooks().getLLVMSyncScopeID(
-                                            getLangOpts(), ScopeModel->map(Scp),
-                                            Ordering, getLLVMContext()));
+          llvm::FenceInst *Fence = Builder.CreateFence(
+              Ordering, getTargetHooks().getLLVMSyncScopeID(
+                            getLangOpts(), ScopeModel->map(Scp), Ordering,
+                            getLLVMContext()));
+          getTargetHooks().setTargetAtomicMetadata(*this, *Fence);
           Builder.CreateBr(ContBB);
         }
       }
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index b70667d04d1f6..e150f5da61f2e 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -778,6 +778,7 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
   bool noinline = false;
   bool alwaysinline = false;
   bool noconvergent = false;
+  StringRef amdgcnAVMode;
   HLSLControlFlowHintAttr::Spelling flattenOrBranch =
       HLSLControlFlowHintAttr::SpellingNotCalculated;
   const CallExpr *musttail = nullptr;
@@ -815,6 +816,9 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
     case attr::Atomic:
       AA = cast<AtomicAttr>(A);
       break;
+    case attr::AMDGCNAV:
+      amdgcnAVMode = cast<AMDGCNAVAttr>(A)->getMode();
+      break;
     case attr::HLSLControlFlowHint: {
       flattenOrBranch = cast<HLSLControlFlowHintAttr>(A)->getSemanticSpelling();
     } break;
@@ -824,6 +828,7 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
   SaveAndRestore save_noinline(InNoInlineAttributedStmt, noinline);
   SaveAndRestore save_alwaysinline(InAlwaysInlineAttributedStmt, alwaysinline);
   SaveAndRestore save_noconvergent(InNoConvergentAttributedStmt, noconvergent);
+  SaveAndRestore save_amdgcnav(AMDGCNAVMode, amdgcnAVMode);
   SaveAndRestore save_musttail(MustTailCall, musttail);
   SaveAndRestore save_flattenOrBranch(HLSLControlFlowAttr, flattenOrBranch);
   CGAtomicOptionsRAII AORAII(CGM, AA);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 3ce0ef1235561..fc31ec6aa8a19 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -622,6 +622,10 @@ class CodeGenFunction : public CodeGenTypeCache {
   /// True if the current statement has noconvergent attribute.
   bool InNoConvergentAttributedStmt = false;
 
+  /// The mode string from the amdgcn_av attribute on the current statement,
+  /// or empty if the attribute is not present.
+  StringRef AMDGCNAVMode;
+
   /// HLSL Branch attribute.
   HLSLControlFlowHintAttr::Spelling HLSLControlFlowAttr =
       HLSLControlFlowHintAttr::SpellingNotCalculated;
diff --git a/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp b/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
index a88dbb71b3ddf..3816dd638fe14 100644
--- a/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
+++ b/clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp
@@ -1875,6 +1875,7 @@ Value *CodeGenFunction::EmitAMDGPUBuiltinExpr(unsigned BuiltinID,
     FenceInst *Fence = Builder.CreateFence(AO, SSID);
     if (E->getNumArgs() > 2)
       AddAMDGPUFenceAddressSpaceMMRA(Fence, E);
+    getTargetHooks().setTargetAtomicMetadata(*this, *Fence);
     return Fence;
   }
   case AMDGPU::BI__builtin_amdgcn_atomic_inc32:
diff --git a/clang/lib/CodeGen/Targets/AMDGPU.cpp b/clang/lib/CodeGen/Targets/AMDGPU.cpp
index 0d36f166328c7..4a9ae3ab8f7f9 100644
--- a/clang/lib/CodeGen/Targets/AMDGPU.cpp
+++ b/clang/lib/CodeGen/Targets/AMDGPU.cpp
@@ -10,6 +10,7 @@
 #include "TargetInfo.h"
 #include "clang/AST/DeclCXX.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/IR/MemoryModelRelaxationAnnotations.h"
 #include "llvm/Support/AMDGPUAddrSpace.h"
 
 using namespace clang;
@@ -633,6 +634,11 @@ void AMDGPUTargetCodeGenInfo::setTargetAtomicMetadata(
     AtomicInst.setMetadata(llvm::LLVMContext::MD_noalias_addrspace, ASRange);
   }
 
+  if (!CGF.AMDGCNAVMode.empty()) {
+    llvm::MMRAMetadata::appendTag(AtomicInst,
+                                  {{"amdgcn-av", CGF.AMDGCNAVMode}});
+  }
+
   if (!RMW)
     return;
 
diff --git a/clang/lib/Sema/SemaStmtAttr.cpp b/clang/lib/Sema/SemaStmtAttr.cpp
index 58d5332565d10..b13b1d2256a92 100644
--- a/clang/lib/Sema/SemaStmtAttr.cpp
+++ b/clang/lib/Sema/SemaStmtAttr.cpp
@@ -351,6 +351,61 @@ static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A,
   return ::new (S.Context) MustTailAttr(S.Context, A);
 }
 
+/// Return true if St is an atomic operation or fence builtin call.
+static bool isAtomicOp(const Stmt *St) {
+  const Expr *E = dyn_cast<Expr>(St);
+  if (!E)
+    return false;
+
+  E = E->IgnoreParenCasts();
+
+  if (isa<AtomicExpr>(E))
+    return true;
+
+  const CallExpr *CE = dyn_cast<CallExpr>(E);
+  if (!CE)
+    return false;
+
+  unsigned BuiltinID = CE->getBuiltinCallee();
+  switch (BuiltinID) {
+  case Builtin::BI__atomic_thread_fence:
+  case Builtin::BI__atomic_signal_fence:
+  case Builtin::BI__c11_atomic_thread_fence:
+  case Builtin::BI__c11_atomic_signal_fence:
+  case Builtin::BI__scoped_atomic_thread_fence:
+    return true;
+  default:
+    break;
+  }
+
+  // Check for target-specific fence builtins.
+  if (const FunctionDecl *FD = CE->getDirectCallee()) {
+    if (FD->getName() == "__builtin_amdgcn_fence")
+      return true;
+  }
+
+  return false;
+}
+
+static Attr *handleAMDGCNAVAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+                                SourceRange Range) {
+  StringRef Mode;
+  if (!S.checkStringLiteralArgumentAttr(A, 0, Mode))
+    return nullptr;
+
+  if (Mode != "none") {
+    S.Diag(A.getLoc(), diag::warn_attribute_type_not_supported) << A << Mode;
+    return nullptr;
+  }
+
+  if (!isAtomicOp(St)) {
+    S.Diag(A.getLoc(), diag::warn_amdgcn_av_requires_atomic) << A;
+    return nullptr;
+  }
+
+  return ::new (S.Context) AMDGCNAVAttr(S.Context, A, Mode);
+}
+
 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A,
                           SourceRange Range) {
 
@@ -730,6 +785,8 @@ static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
     return handleNoInlineAttr(S, St, A, Range);
   case ParsedAttr::AT_MustTail:
     return handleMustTailAttr(S, St, A, Range);
+  case ParsedAttr::AT_AMDGCNAV:
+    return handleAMDGCNAVAttr(S, St, A, Range);
   case ParsedAttr::AT_Likely:
     return handleLikely(S, St, A, Range);
   case ParsedAttr::AT_Unlikely:
diff --git a/clang/test/CodeGen/AMDGPU/amdgcn-av-non-atomic.cpp b/clang/test/CodeGen/AMDGPU/amdgcn-av-non-atomic.cpp
new file mode 100644
index 0000000000000..1f193a865be97
--- /dev/null
+++ b/clang/test/CodeGen/AMDGPU/amdgcn-av-non-atomic.cpp
@@ -0,0 +1,43 @@
+// REQUIRES: amdgpu-registered-target
+// RUN: %clang_cc1 %s -emit-llvm -O0 -verify -o - \
+// RUN:   -triple=amdgcn-amd-amdhsa | FileCheck %s
+
+// Test that [[clang::amdgcn_av("none")]] on non-atomic statements emits a
+// warning and does NOT produce !mmra metadata.
+
+// CHECK-LABEL: define {{.*}} @_Z16test_plain_storePii(
+// CHECK-NOT: !mmra
+// CHECK: ret void
+void test_plain_store(int *p, int val) {
+  [[clang::amdgcn_av("none")]] *p = val; // expected-warning {{'clang::amdgcn_av' attribute only applies to atomic operations}}
+}
+
+// CHECK-LABEL: define {{.*}} @_Z15test_plain_callv(
+// CHECK-NOT: !mmra
+// CHECK: ret void
+extern void foo();
+void test_plain_call() {
+  [[clang::amdgcn_av("none")]] foo(); // expected-warning {{'clang::amdgcn_av' attribute only applies to atomic operations}}
+}
+
+// CHECK-LABEL: define {{.*}} @_Z18test_for_with_atomPi(
+// CHECK-NOT: !mmra
+// C...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/199622


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