llvm · rampitec · Sep 16, 2025 · Sep 16, 2025
diff --git a/clang/include/clang/Basic/BuiltinsAMDGPU.def b/clang/include/clang/Basic/BuiltinsAMDGPU.def
@@ -696,6 +696,7 @@ TARGET_BUILTIN(__builtin_amdgcn_cvt_sr_f16_f32, "V2hV2hfUiIb", "nc", "f32-to-f16
 //===----------------------------------------------------------------------===//
 // GFX1250+ only builtins.
 //===----------------------------------------------------------------------===//
+TARGET_BUILTIN(__builtin_amdgcn_s_cluster_barrier, "v", "n", "gfx1250-insts")
 
 TARGET_BUILTIN(__builtin_amdgcn_flat_prefetch, "vvC*0Ii", "nc", "vmem-pref-insts")
 TARGET_BUILTIN(__builtin_amdgcn_global_prefetch, "vvC*1Ii", "nc", "vmem-pref-insts")

diff --git a/clang/test/CodeGenOpenCL/builtins-amdgcn-gfx1250.cl b/clang/test/CodeGenOpenCL/builtins-amdgcn-gfx1250.cl
@@ -1478,6 +1478,16 @@ void test_prefetch(generic void *fptr, global void *gptr) {
   __builtin_amdgcn_global_prefetch(gptr, 8);
 }
 
+// CHECK-LABEL: @test_s_cluster_barrier(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    call void @llvm.amdgcn.s.cluster.barrier()
+// CHECK-NEXT:    ret void
+//
+void test_s_cluster_barrier()
+{
+  __builtin_amdgcn_s_cluster_barrier();
+}
+
 // CHECK-LABEL: @test_global_add_f32(
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    [[RETVAL:%.*]] = alloca float, align 4, addrspace(5)

diff --git a/llvm/include/llvm/IR/IntrinsicsAMDGPU.td b/llvm/include/llvm/IR/IntrinsicsAMDGPU.td
@@ -3691,6 +3691,10 @@ def int_amdgcn_ashr_pk_u8_i32 : ClangBuiltin<"__builtin_amdgcn_ashr_pk_u8_i32">,
 // gfx1250 intrinsics
 // ===----------------------------------------------------------------------===//
 
+// Vanilla cluster sync-barrier
+def int_amdgcn_s_cluster_barrier : ClangBuiltin<"__builtin_amdgcn_s_cluster_barrier">,
+  Intrinsic<[], [], [IntrNoMem, IntrHasSideEffects, IntrConvergent, IntrWillReturn, IntrNoCallback, IntrNoFree]>;
+
 // Async waits decrement ASYNCcnt and tensor waits decrement TENSORcnt which is
 // modeled as InaccessibleMem.
 class AMDGPUWaitAsyncIntrinsic :

diff --git a/llvm/lib/Target/AMDGPU/AMDGPULowerIntrinsics.cpp b/llvm/lib/Target/AMDGPU/AMDGPULowerIntrinsics.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/IntrinsicsAMDGPU.h"
 #include "llvm/InitializePasses.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 #define DEBUG_TYPE "amdgpu-lower-intrinsics"
 
@@ -49,7 +50,6 @@ class AMDGPULowerIntrinsicsLegacy : public ModulePass {
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<TargetPassConfig>();
-    AU.setPreservesCFG();
   }
 };
 
@@ -73,6 +73,7 @@ bool AMDGPULowerIntrinsicsImpl::run() {
     case Intrinsic::amdgcn_s_barrier_signal:
     case Intrinsic::amdgcn_s_barrier_signal_isfirst:
     case Intrinsic::amdgcn_s_barrier_wait:
+    case Intrinsic::amdgcn_s_cluster_barrier:
       forEachCall(F, [&](IntrinsicInst *II) { Changed |= visitBarrier(*II); });
       break;
     }
@@ -81,13 +82,14 @@ bool AMDGPULowerIntrinsicsImpl::run() {
   return Changed;
 }
 
-// Optimize barriers and lower s_barrier to a sequence of split barrier
-// intrinsics.
+// Optimize barriers and lower s_(cluster_)barrier to a sequence of split
+// barrier intrinsics.
 bool AMDGPULowerIntrinsicsImpl::visitBarrier(IntrinsicInst &I) {
   assert(I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier ||
          I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_signal ||
          I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_signal_isfirst ||
-         I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_wait);
+         I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_wait ||
+         I.getIntrinsicID() == Intrinsic::amdgcn_s_cluster_barrier);
 
   const GCNSubtarget &ST = TM.getSubtarget<GCNSubtarget>(*I.getFunction());
   bool IsSingleWaveWG = false;
@@ -99,7 +101,59 @@ bool AMDGPULowerIntrinsicsImpl::visitBarrier(IntrinsicInst &I) {
 
   IRBuilder<> B(&I);
 
-  if (IsSingleWaveWG) {
+  // Lower the s_cluster_barrier intrinsic first. There is no corresponding
+  // hardware instruction in any subtarget.
+  if (I.getIntrinsicID() == Intrinsic::amdgcn_s_cluster_barrier) {
+    // The default cluster barrier expects one signal per workgroup. So we need
+    // a workgroup barrier first.
+    if (IsSingleWaveWG) {
+      B.CreateIntrinsic(B.getVoidTy(), Intrinsic::amdgcn_wave_barrier, {});
+    } else {
+      Value *BarrierID_32 = B.getInt32(AMDGPU::Barrier::WORKGROUP);
+      Value *BarrierID_16 = B.getInt16(AMDGPU::Barrier::WORKGROUP);
+      Value *IsFirst = B.CreateIntrinsic(
+          B.getInt1Ty(), Intrinsic::amdgcn_s_barrier_signal_isfirst,
+          {BarrierID_32});
+      B.CreateIntrinsic(B.getVoidTy(), Intrinsic::amdgcn_s_barrier_wait,
+                        {BarrierID_16});
+
+      Instruction *ThenTerm =
+          SplitBlockAndInsertIfThen(IsFirst, I.getIterator(), false);
+      B.SetInsertPoint(ThenTerm);
+    }
+
+    // Now we can signal the cluster barrier from a single wave and wait for the
+    // barrier in all waves.
+    Value *BarrierID_32 = B.getInt32(AMDGPU::Barrier::CLUSTER);
+    Value *BarrierID_16 = B.getInt16(AMDGPU::Barrier::CLUSTER);
+    B.CreateIntrinsic(B.getVoidTy(), Intrinsic::amdgcn_s_barrier_signal,
+                      {BarrierID_32});
+
+    B.SetInsertPoint(&I);
+    B.CreateIntrinsic(B.getVoidTy(), Intrinsic::amdgcn_s_barrier_wait,
+                      {BarrierID_16});
+
+    I.eraseFromParent();
+    return true;
+  }
+
+  bool IsWorkgroupScope = false;
+
+  if (I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_wait ||
+      I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_signal ||
+      I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_signal_isfirst) {
+    int BarrierID = cast<ConstantInt>(I.getArgOperand(0))->getSExtValue();
+    if (BarrierID == AMDGPU::Barrier::TRAP ||
+        BarrierID == AMDGPU::Barrier::WORKGROUP ||
+        (BarrierID >= AMDGPU::Barrier::NAMED_BARRIER_FIRST &&
+         BarrierID <= AMDGPU::Barrier::NAMED_BARRIER_LAST))
+      IsWorkgroupScope = true;
+  } else {
+    assert(I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier);
+    IsWorkgroupScope = true;
+  }
+
+  if (IsWorkgroupScope && IsSingleWaveWG) {
     // Down-grade waits, remove split signals.
     if (I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier ||
         I.getIntrinsicID() == Intrinsic::amdgcn_s_barrier_wait) {
@@ -134,9 +188,7 @@ PreservedAnalyses AMDGPULowerIntrinsicsPass::run(Module &M,
   AMDGPULowerIntrinsicsImpl Impl(M, TM);
   if (!Impl.run())
     return PreservedAnalyses::all();
-  PreservedAnalyses PA;
-  PA.preserveSet<CFGAnalyses>();
-  return PA;
+  return PreservedAnalyses::none();
 }
 
 bool AMDGPULowerIntrinsicsLegacy::runOnModule(Module &M) {

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUMemoryUtils.cpp b/llvm/lib/Target/AMDGPU/AMDGPUMemoryUtils.cpp
@@ -360,6 +360,7 @@ bool isReallyAClobber(const Value *Ptr, MemoryDef *Def, AAResults *AA) {
   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
     switch (II->getIntrinsicID()) {
     case Intrinsic::amdgcn_s_barrier:
+    case Intrinsic::amdgcn_s_cluster_barrier:
     case Intrinsic::amdgcn_s_barrier_signal:
     case Intrinsic::amdgcn_s_barrier_signal_var:
     case Intrinsic::amdgcn_s_barrier_signal_isfirst:

diff --git a/llvm/lib/Target/AMDGPU/SIDefines.h b/llvm/lib/Target/AMDGPU/SIDefines.h
@@ -1108,7 +1108,14 @@ enum Register_Flag : uint8_t {
 namespace AMDGPU {
 namespace Barrier {
 
-enum Type { TRAP = -2, WORKGROUP = -1 };
+enum Type {
+  CLUSTER_TRAP = -4,
+  CLUSTER = -3,
+  TRAP = -2,
+  WORKGROUP = -1,
+  NAMED_BARRIER_FIRST = 1,
+  NAMED_BARRIER_LAST = 16,
+};
 
 enum {
   BARRIER_SCOPE_WORKGROUP = 0,

diff --git a/llvm/test/CodeGen/AMDGPU/lower-intrinsics-cluster-barrier.ll b/llvm/test/CodeGen/AMDGPU/lower-intrinsics-cluster-barrier.ll
@@ -0,0 +1,107 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=amdgpu-lower-intrinsics -S -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1250 -codegen-opt-level=0 | FileCheck --check-prefixes=CHECK,NOOPT %s
+; RUN: opt < %s -passes=amdgpu-lower-intrinsics -S -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1250 -codegen-opt-level=1 -mattr=+wavefrontsize32 | FileCheck --check-prefixes=CHECK,OPT-WAVE32 %s
+; RUN: opt < %s -passes=amdgpu-lower-intrinsics -S -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1250 -codegen-opt-level=1 -mattr=+wavefrontsize64 | FileCheck --check-prefixes=CHECK,OPT-WAVE64 %s
+
+declare void @foo(i1)
+
+; Verify that the explicit use of a split cluster barrier isn't optimized away.
+define amdgpu_kernel void @split_barriers() "amdgpu-flat-work-group-size"="32,32" {
+; CHECK-LABEL: define amdgpu_kernel void @split_barriers(
+; CHECK-SAME: ) #[[ATTR1:[0-9]+]] {
+; CHECK-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; CHECK-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; CHECK-NEXT:    [[ISFIRST:%.*]] = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -3)
+; CHECK-NEXT:    call void @foo(i1 [[ISFIRST]])
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+  call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+  %isfirst = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -3)
+  call void @foo(i1 %isfirst)
+  ret void
+}
+
+define amdgpu_kernel void @s_cluster_barrier() {
+; CHECK-LABEL: define amdgpu_kernel void @s_cluster_barrier(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[TMP1:%.*]] = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -1)
+; CHECK-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -1)
+; CHECK-NEXT:    br i1 [[TMP1]], label %[[BB2:.*]], label %[[BB3:.*]]
+; CHECK:       [[BB2]]:
+; CHECK-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; CHECK-NEXT:    br label %[[BB3]]
+; CHECK:       [[BB3]]:
+; CHECK-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.amdgcn.s.cluster.barrier()
+  ret void
+}
+
+define amdgpu_kernel void @s_cluster_barrier_wg32() "amdgpu-flat-work-group-size"="32,32" {
+; NOOPT-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg32(
+; NOOPT-SAME: ) #[[ATTR1]] {
+; NOOPT-NEXT:    [[TMP1:%.*]] = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -1)
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -1)
+; NOOPT-NEXT:    br i1 [[TMP1]], label %[[BB2:.*]], label %[[BB3:.*]]
+; NOOPT:       [[BB2]]:
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; NOOPT-NEXT:    br label %[[BB3]]
+; NOOPT:       [[BB3]]:
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; NOOPT-NEXT:    ret void
+;
+; OPT-WAVE32-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg32(
+; OPT-WAVE32-SAME: ) #[[ATTR1]] {
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.wave.barrier()
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; OPT-WAVE32-NEXT:    ret void
+;
+; OPT-WAVE64-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg32(
+; OPT-WAVE64-SAME: ) #[[ATTR1]] {
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.wave.barrier()
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; OPT-WAVE64-NEXT:    ret void
+;
+  call void @llvm.amdgcn.s.cluster.barrier()
+  ret void
+}
+
+define amdgpu_kernel void @s_cluster_barrier_wg64() "amdgpu-flat-work-group-size"="64,64" {
+; NOOPT-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg64(
+; NOOPT-SAME: ) #[[ATTR2:[0-9]+]] {
+; NOOPT-NEXT:    [[TMP1:%.*]] = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -1)
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -1)
+; NOOPT-NEXT:    br i1 [[TMP1]], label %[[BB2:.*]], label %[[BB3:.*]]
+; NOOPT:       [[BB2]]:
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; NOOPT-NEXT:    br label %[[BB3]]
+; NOOPT:       [[BB3]]:
+; NOOPT-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; NOOPT-NEXT:    ret void
+;
+; OPT-WAVE32-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg64(
+; OPT-WAVE32-SAME: ) #[[ATTR2:[0-9]+]] {
+; OPT-WAVE32-NEXT:    [[TMP1:%.*]] = call i1 @llvm.amdgcn.s.barrier.signal.isfirst(i32 -1)
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -1)
+; OPT-WAVE32-NEXT:    br i1 [[TMP1]], label %[[BB2:.*]], label %[[BB3:.*]]
+; OPT-WAVE32:       [[BB2]]:
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; OPT-WAVE32-NEXT:    br label %[[BB3]]
+; OPT-WAVE32:       [[BB3]]:
+; OPT-WAVE32-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; OPT-WAVE32-NEXT:    ret void
+;
+; OPT-WAVE64-LABEL: define amdgpu_kernel void @s_cluster_barrier_wg64(
+; OPT-WAVE64-SAME: ) #[[ATTR2:[0-9]+]] {
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.wave.barrier()
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.s.barrier.signal(i32 -3)
+; OPT-WAVE64-NEXT:    call void @llvm.amdgcn.s.barrier.wait(i16 -3)
+; OPT-WAVE64-NEXT:    ret void
+;
+  call void @llvm.amdgcn.s.cluster.barrier()
+  ret void
+}