[Mlir-commits] [mlir] [MLIR] Add the convergent attribute to the barrier and shuffle ops (PR #97807)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir-gpu

Author: Finlay (FMarno)

<details>
<summary>Changes</summary>

When lowering from the gpu dialect to the llvm dialect for spirv, the barrier op and shuffle ops need a convergent attribute for correctness.

---
Full diff: https://github.com/llvm/llvm-project/pull/97807.diff


2 Files Affected:

- (modified) mlir/lib/Conversion/GPUToLLVMSPV/GPUToLLVMSPV.cpp (+8-5) 
- (modified) mlir/test/Conversion/GPUToLLVMSPV/gpu-to-llvm-spv.mlir (+9-9) 


``````````diff
diff --git a/mlir/lib/Conversion/GPUToLLVMSPV/GPUToLLVMSPV.cpp b/mlir/lib/Conversion/GPUToLLVMSPV/GPUToLLVMSPV.cpp
index 30812a330ef18..ebeb8f803d71d 100644
--- a/mlir/lib/Conversion/GPUToLLVMSPV/GPUToLLVMSPV.cpp
+++ b/mlir/lib/Conversion/GPUToLLVMSPV/GPUToLLVMSPV.cpp
@@ -43,7 +43,8 @@ namespace mlir {
 static LLVM::LLVMFuncOp lookupOrCreateSPIRVFn(Operation *symbolTable,
                                               StringRef name,
                                               ArrayRef<Type> paramTypes,
-                                              Type resultType) {
+                                              Type resultType,
+                                              bool isConvergent = false) {
   auto func = dyn_cast_or_null<LLVM::LLVMFuncOp>(
       SymbolTable::lookupSymbolIn(symbolTable, name));
   if (!func) {
@@ -52,6 +53,7 @@ static LLVM::LLVMFuncOp lookupOrCreateSPIRVFn(Operation *symbolTable,
         symbolTable->getLoc(), name,
         LLVM::LLVMFunctionType::get(resultType, paramTypes));
     func.setCConv(LLVM::cconv::CConv::SPIR_FUNC);
+    func.setConvergent(isConvergent);
   }
   return func;
 }
@@ -89,8 +91,8 @@ struct GPUBarrierConversion final : ConvertOpToLLVMPattern<gpu::BarrierOp> {
     assert(moduleOp && "Expecting module");
     Type flagTy = rewriter.getI32Type();
     Type voidTy = rewriter.getType<LLVM::LLVMVoidType>();
-    LLVM::LLVMFuncOp func =
-        lookupOrCreateSPIRVFn(moduleOp, funcName, flagTy, voidTy);
+    LLVM::LLVMFuncOp func = lookupOrCreateSPIRVFn(
+        moduleOp, funcName, flagTy, voidTy, /*isConvergent=*/true);
 
     // Value used by SPIR-V backend to represent `CLK_LOCAL_MEM_FENCE`.
     // See `llvm/lib/Target/SPIRV/SPIRVBuiltins.td`.
@@ -266,8 +268,9 @@ struct GPUShuffleConversion final : ConvertOpToLLVMPattern<gpu::ShuffleOp> {
     Type valueType = adaptor.getValue().getType();
     Type offsetType = adaptor.getOffset().getType();
     Type resultType = valueType;
-    LLVM::LLVMFuncOp func = lookupOrCreateSPIRVFn(
-        moduleOp, funcName, {valueType, offsetType}, resultType);
+    LLVM::LLVMFuncOp func =
+        lookupOrCreateSPIRVFn(moduleOp, funcName, {valueType, offsetType},
+                              resultType, /*isConvergent=*/true);
 
     Location loc = op->getLoc();
     std::array<Value, 2> args{adaptor.getValue(), adaptor.getOffset()};
diff --git a/mlir/test/Conversion/GPUToLLVMSPV/gpu-to-llvm-spv.mlir b/mlir/test/Conversion/GPUToLLVMSPV/gpu-to-llvm-spv.mlir
index 654041b8e9aac..1b0f89a9a573e 100644
--- a/mlir/test/Conversion/GPUToLLVMSPV/gpu-to-llvm-spv.mlir
+++ b/mlir/test/Conversion/GPUToLLVMSPV/gpu-to-llvm-spv.mlir
@@ -104,7 +104,7 @@ gpu.module @builtins {
 // -----
 
 gpu.module @barriers {
-  // CHECK:       llvm.func spir_funccc @_Z7barrierj(i32)
+  // CHECK:       llvm.func spir_funccc @_Z7barrierj(i32) attributes {convergent}
 
   // CHECK-LABEL: gpu_barrier
   func.func @gpu_barrier() {
@@ -120,10 +120,10 @@ gpu.module @barriers {
 // Check `gpu.shuffle` conversion with default subgroup size.
 
 gpu.module @shuffles {
-  // CHECK:       llvm.func spir_funccc @_Z22sub_group_shuffle_downdj(f64, i32) -> f64
-  // CHECK:       llvm.func spir_funccc @_Z20sub_group_shuffle_upfj(f32, i32) -> f32
-  // CHECK:       llvm.func spir_funccc @_Z21sub_group_shuffle_xorlj(i64, i32) -> i64
-  // CHECK:       llvm.func spir_funccc @_Z17sub_group_shuffleij(i32, i32) -> i32
+  // CHECK:       llvm.func spir_funccc @_Z22sub_group_shuffle_downdj(f64, i32) -> f64 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z20sub_group_shuffle_upfj(f32, i32) -> f32 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z21sub_group_shuffle_xorlj(i64, i32) -> i64 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z17sub_group_shuffleij(i32, i32) -> i32 attributes {convergent}
 
   // CHECK-LABEL: gpu_shuffles
   // CHECK-SAME:              (%[[VAL_0:.*]]: i32, %[[VAL_1:.*]]: i32, %[[VAL_2:.*]]: i64, %[[VAL_3:.*]]: i32, %[[VAL_4:.*]]: f32, %[[VAL_5:.*]]: i32, %[[VAL_6:.*]]: f64, %[[VAL_7:.*]]: i32)
@@ -155,10 +155,10 @@ gpu.module @shuffles {
 gpu.module @shuffles attributes {
   spirv.target_env = #spirv.target_env<#spirv.vce<v1.4, [Kernel, Addresses, GroupNonUniformShuffle, Int64], []>, #spirv.resource_limits<subgroup_size = 16>>
 } {
-  // CHECK:       llvm.func spir_funccc @_Z22sub_group_shuffle_downdj(f64, i32) -> f64
-  // CHECK:       llvm.func spir_funccc @_Z20sub_group_shuffle_upfj(f32, i32) -> f32
-  // CHECK:       llvm.func spir_funccc @_Z21sub_group_shuffle_xorlj(i64, i32) -> i64
-  // CHECK:       llvm.func spir_funccc @_Z17sub_group_shuffleij(i32, i32) -> i32
+  // CHECK:       llvm.func spir_funccc @_Z22sub_group_shuffle_downdj(f64, i32) -> f64 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z20sub_group_shuffle_upfj(f32, i32) -> f32 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z21sub_group_shuffle_xorlj(i64, i32) -> i64 attributes {convergent}
+  // CHECK:       llvm.func spir_funccc @_Z17sub_group_shuffleij(i32, i32) -> i32 attributes {convergent}
 
   // CHECK-LABEL: gpu_shuffles
   // CHECK-SAME:              (%[[VAL_0:.*]]: i32, %[[VAL_1:.*]]: i32, %[[VAL_2:.*]]: i64, %[[VAL_3:.*]]: i32, %[[VAL_4:.*]]: f32, %[[VAL_5:.*]]: i32, %[[VAL_6:.*]]: f64, %[[VAL_7:.*]]: i32)

``````````

</details>


https://github.com/llvm/llvm-project/pull/97807