[mlir][AMDGPU] Define atomic compare-and-swap for raw buffers

This commit adds the buffer cmpswap intrinsic to the ROCDL dialect and
its corresponding AMDGPU dialect wrappers.

Reviewed By: nirvedhmeshram

Differential Revision: https://reviews.llvm.org/D148722

mlir/include/mlir/Dialect/AMDGPU/AMDGPU.td

@@ -136,6 +136,48 @@ def AMDGPU_RawBufferStoreOp :
   let hasVerifier = 1;
 }
 
+// Raw buffer atomic compare-and-swap
+def AMDGPU_RawBufferAtomicCmpswapOp :
+    AMDGPU_Op<"raw_buffer_atomic_cmpswap", [
+      AttrSizedOperandSegments,
+      AllTypesMatch<["src", "cmp", "value"]>,
+      AllElementTypesMatch<["value", "memref"]>]>,
+    Arguments<(ins AnyTypeOf<[I32, I64, F32, F64]>:$src,
+                   AnyType:$cmp,
+                   Arg<AnyMemRef, "buffer to operate on", [MemRead, MemWrite]>:$memref,
+                   Variadic<I32>:$indices,
+                   DefaultValuedAttr<BoolAttr, "true">:$boundsCheck,
+                   OptionalAttr<I32Attr>:$indexOffset,
+                   Optional<I32>:$sgprOffset)>,
+    Results<(outs AnyType:$value)> {
+
+  let summary = "Raw Buffer Atomic compare-and-swap";
+  let description = [{
+    The `amdgpu.raw_buffer_atomic_cmpswap` op is a wrapper around the
+    buffer-based atomic compare-and-swap min available on AMD GPUs.
+
+    The index into the buffer is computed as for `memref.store` with the addition
+    of `indexOffset` (which is used to aid in emitting vectorized code) and,
+    if present `sgprOffset` (which is added after bounds checks and includes
+    any non-zero offset on the memref type).
+
+    All indexing components are given in terms of the memref's element size, not
+    the byte lengths required by the intrinsic.
+
+    Out of bounds atomic operations are ignored in hardware.
+
+    See `amdgpu.raw_buffer_load` for a description of how the underlying
+    instruction is constructed.
+  }];
+  let assemblyFormat = [{
+    attr-dict $src `,` $cmp `->` $memref `[` $indices `]`
+      (`sgprOffset` $sgprOffset^)? `:`
+      type($value) `->` type($memref) `,` type($indices)
+  }];
+  let hasCanonicalizer = 1;
+  let hasVerifier = 1;
+}
+
 // Raw buffer atomic floating point add
 def AMDGPU_RawBufferAtomicFaddOp :
     AMDGPU_Op<"raw_buffer_atomic_fadd", [AllElementTypesMatch<["value", "memref"]>,

mlir/include/mlir/Dialect/LLVMIR/ROCDLOps.td

@@ -252,6 +252,25 @@ def ROCDL_RawBufferStoreOp :
   let hasCustomAssemblyFormat = 1;
 }
 
+def ROCDL_RawBufferAtomicCmpSwap :
+  ROCDL_Op<"raw.buffer.atomic.cmpswap", [AllTypesMatch<["res", "src", "cmp"]>]>,
+  Results<(outs LLVM_Type:$res)>,
+  Arguments<(ins LLVM_Type:$src,
+                 LLVM_Type:$cmp,
+                 LLVM_Type:$rsrc,
+                 I32:$offset,
+                 I32:$soffset,
+                 I32:$aux)>{
+  string llvmBuilder = [{
+      $res = createIntrinsicCall(builder,
+          llvm::Intrinsic::amdgcn_raw_buffer_atomic_cmpswap, {$src, $cmp, $rsrc,
+            $offset, $soffset, $aux}, {$_resultType});
+  }];
+  let assemblyFormat = [{
+    attr-dict `(` operands `)` `:` type($res) `,` type($rsrc)
+  }];
+}
+
 //===---------------------------------------------------------------------===//
 // MI-100 and MI-200 buffer atomic floating point add intrinsic
 

mlir/lib/Conversion/AMDGPUToROCDL/AMDGPUToROCDL.cpp

@@ -62,6 +62,14 @@ struct RawBufferOpLowering : public ConvertOpToLLVMPattern<GpuOp> {
     else
       wantedDataType = gpuOp.getODSResults(0)[0].getType();
 
+    Value atomicCmpData = Value();
+    // Operand index 1 of a load is the indices, trying to read them can crash.
+    if (storeData) {
+      Value maybeCmpData = adaptor.getODSOperands(1)[0];
+      if (maybeCmpData != memref)
+        atomicCmpData = maybeCmpData;
+    }
+
     Type llvmWantedDataType = this->typeConverter->convertType(wantedDataType);
 
     Type i32 = rewriter.getI32Type();
@@ -73,8 +81,16 @@ struct RawBufferOpLowering : public ConvertOpToLLVMPattern<GpuOp> {
     // If we want to load a vector<NxT> with total size <= 32
     // bits, use a scalar load and bitcast it. Similarly, if bitsize(T) < 32
     // and the total load size is >= 32, use a vector load of N / (bitsize(T) /
-    // 32) x i32 and bitcast.
+    // 32) x i32 and bitcast. Also, the CAS intrinsic requires integer operands,
+    // so bitcast any floats to integers.
     Type llvmBufferValType = llvmWantedDataType;
+    if (atomicCmpData) {
+      if (wantedDataType.isa<VectorType>())
+        return gpuOp.emitOpError("vector compare-and-swap does not exist");
+      if (auto floatType = wantedDataType.dyn_cast<FloatType>())
+        llvmBufferValType = this->getTypeConverter()->convertType(
+            rewriter.getIntegerType(floatType.getWidth()));
+    }
     if (auto dataVector = wantedDataType.dyn_cast<VectorType>()) {
       uint32_t elemBits = dataVector.getElementTypeBitWidth();
       uint32_t totalBits = elemBits * dataVector.getNumElements();
@@ -109,6 +125,16 @@ struct RawBufferOpLowering : public ConvertOpToLLVMPattern<GpuOp> {
       }
     }
 
+    if (atomicCmpData) {
+      if (llvmBufferValType != llvmWantedDataType) {
+        Value castForCmp = rewriter.create<LLVM::BitcastOp>(
+            loc, llvmBufferValType, atomicCmpData);
+        args.push_back(castForCmp);
+      } else {
+        args.push_back(atomicCmpData);
+      }
+    }
+
     // Construct buffer descriptor from memref, attributes
     int64_t offset = 0;
     SmallVector<int64_t, 5> strides;
@@ -529,6 +555,8 @@ void mlir::populateAMDGPUToROCDLConversionPatterns(LLVMTypeConverter &converter,
       RawBufferOpLowering<RawBufferAtomicFmaxOp, ROCDL::RawBufferAtomicFMaxOp>,
       RawBufferOpLowering<RawBufferAtomicSmaxOp, ROCDL::RawBufferAtomicSMaxOp>,
       RawBufferOpLowering<RawBufferAtomicUminOp, ROCDL::RawBufferAtomicUMinOp>,
+      RawBufferOpLowering<RawBufferAtomicCmpswapOp,
+                          ROCDL::RawBufferAtomicCmpSwap>,
       MFMAOpLowering>(converter, chipset);
 }
 

mlir/lib/Dialect/AMDGPU/IR/AMDGPUDialect.cpp

@@ -90,6 +90,10 @@ LogicalResult RawBufferAtomicUminOp::verify() {
   return verifyRawBufferOp(*this);
 }
 
+LogicalResult RawBufferAtomicCmpswapOp::verify() {
+  return verifyRawBufferOp(*this);
+}
+
 static std::optional<uint32_t> getConstantUint32(Value v) {
   APInt cst;
   if (!v.getType().isInteger(32))
@@ -136,12 +140,11 @@ static bool staticallyOutOfBounds(OpType op) {
 }
 
 namespace {
-struct RemoveStaticallyOobBufferLoads final
-    : public OpRewritePattern<RawBufferLoadOp> {
-  using OpRewritePattern<RawBufferLoadOp>::OpRewritePattern;
+template <typename OpType>
+struct RemoveStaticallyOobBufferLoads final : public OpRewritePattern<OpType> {
+  using OpRewritePattern<OpType>::OpRewritePattern;
 
-  LogicalResult matchAndRewrite(RawBufferLoadOp op,
-                                PatternRewriter &rw) const override {
+  LogicalResult matchAndRewrite(OpType op, PatternRewriter &rw) const override {
     if (!staticallyOutOfBounds(op))
       return failure();
     Type loadType = op.getResult().getType();
@@ -167,7 +170,7 @@ struct RemoveStaticallyOobBufferWrites final : public OpRewritePattern<OpType> {
 
 void RawBufferLoadOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                                   MLIRContext *context) {
-  results.add<RemoveStaticallyOobBufferLoads>(context);
+  results.add<RemoveStaticallyOobBufferLoads<RawBufferLoadOp>>(context);
 }
 
 void RawBufferStoreOp::getCanonicalizationPatterns(RewritePatternSet &results,
@@ -195,6 +198,12 @@ void RawBufferAtomicUminOp::getCanonicalizationPatterns(
   results.add<RemoveStaticallyOobBufferWrites<RawBufferAtomicUminOp>>(context);
 }
 
+void RawBufferAtomicCmpswapOp::getCanonicalizationPatterns(
+    RewritePatternSet &results, MLIRContext *context) {
+  results.add<RemoveStaticallyOobBufferLoads<RawBufferAtomicCmpswapOp>>(
+      context);
+}
+
 //===----------------------------------------------------------------------===//
 // MFMAOp
 //===----------------------------------------------------------------------===//

mlir/test/Conversion/AMDGPUToROCDL/amdgpu-to-rocdl.mlir

@@ -197,6 +197,35 @@ func.func @gpu_gcn_raw_buffer_atomic_umin_i32(%value: i32, %buf: memref<64xi32>,
   func.return
 }
 
+// CHECK-LABEL: func @amdgpu_raw_buffer_atomic_cmpswap_f32
+// CHECK-SAME: (%[[src:.*]]: f32, %[[cmp:.*]]: f32, {{.*}})
+func.func @amdgpu_raw_buffer_atomic_cmpswap_f32(%src : f32, %cmp : f32, %buf : memref<64xf32>, %idx: i32) -> f32 {
+  // CHECK: %[[srcCast:.*]] = llvm.bitcast %[[src]] : f32 to i32
+  // CHECK: %[[cmpCast:.*]] = llvm.bitcast %[[cmp]] : f32 to i32
+  // CHECK: %[[numRecords:.*]] = llvm.mlir.constant(256 : i32)
+  // CHECK: llvm.insertelement{{.*}}%[[numRecords]]
+  // CHECK: %[[word3:.*]] = llvm.mlir.constant(159744 : i32)
+  // CHECK: %[[resource:.*]] = llvm.insertelement{{.*}}%[[word3]]
+  // CHECK: %[[dst:.*]] = rocdl.raw.buffer.atomic.cmpswap(%[[srcCast]], %[[cmpCast]], %[[resource]], %{{.*}}, %{{.*}}, %{{.*}}) : i32, vector<4xi32>
+  // CHECK: %[[dstCast:.*]] = llvm.bitcast %[[dst]] : i32 to f32
+  // CHECK: return %[[dstCast]]
+  %dst = amdgpu.raw_buffer_atomic_cmpswap {boundsCheck = true} %src, %cmp -> %buf[%idx] : f32 -> memref<64xf32>, i32
+  func.return %dst : f32
+}
+
+// CHECK-LABEL: func @amdgpu_raw_buffer_atomic_cmpswap_i64
+// CHECK-SAME: (%[[src:.*]]: i64, %[[cmp:.*]]: i64, {{.*}})
+func.func @amdgpu_raw_buffer_atomic_cmpswap_i64(%src : i64, %cmp : i64, %buf : memref<64xi64>, %idx: i32) -> i64 {
+  // CHECK: %[[numRecords:.*]] = llvm.mlir.constant(512 : i32)
+  // CHECK: llvm.insertelement{{.*}}%[[numRecords]]
+  // CHECK: %[[word3:.*]] = llvm.mlir.constant(159744 : i32)
+  // CHECK: %[[resource:.*]] = llvm.insertelement{{.*}}%[[word3]]
+  // CHECK: %[[dst:.*]] = rocdl.raw.buffer.atomic.cmpswap(%[[src]], %[[cmp]], %[[resource]], %{{.*}}, %{{.*}}, %{{.*}}) : i64, vector<4xi32>
+  // CHECK: return %[[dst]]
+  %dst = amdgpu.raw_buffer_atomic_cmpswap {boundsCheck = true} %src, %cmp -> %buf[%idx] : i64 -> memref<64xi64>, i32
+  func.return %dst : i64
+}
+
 // CHECK-LABEL: func @lds_barrier
 func.func @lds_barrier() {
   // CHECK: llvm.inline_asm has_side_effects asm_dialect = att "s_waitcnt lgkmcnt(0)\0As_barrier"

mlir/test/Dialect/AMDGPU/ops.mlir

@@ -74,6 +74,13 @@ func.func @raw_buffer_atomic_fadd_f32_to_rank_4(%value : f32, %dst : memref<128x
   func.return
 }
 
+// CHECK-LABEL: func @raw_buffer_atomic_cmpswap_f32
+func.func @raw_buffer_atomic_cmpswap_f32(%src : f32, %cmp : f32, %dst : memref<128x64x32x16xf32>, %offset : i32, %idx0 : i32, %idx1 : i32, %idx2 : i32, %idx3 : i32) {
+  // CHECK: amdgpu.raw_buffer_atomic_cmpswap {indexOffset = 1 : i32} %{{.*}}, %{{.*}} -> %{{.*}}[%{{.*}}, %{{.*}}, %{{.*}}] sgprOffset %{{.*}} : f32 -> memref<128x64x32x16xf32>, i32, i32, i32, i32
+  amdgpu.raw_buffer_atomic_cmpswap {boundsCheck = true, indexOffset = 1 : i32} %src, %cmp -> %dst[%idx0, %idx1, %idx2, %idx3] sgprOffset %offset : f32 -> memref<128x64x32x16xf32>, i32, i32, i32, i32
+  func.return
+}
+
 // CHECK-LABEL: func @lds_barrier
 func.func @lds_barrier() {
   // CHECK: amdgpu.lds_barrier

mlir/test/Dialect/LLVMIR/rocdl.mlir

@@ -262,9 +262,11 @@ llvm.func @rocdl.raw.buffer.i32(%rsrc : vector<4xi32>,
   // CHECK-LABEL: rocdl.raw.buffer.i32
   // CHECK: rocdl.raw.buffer.atomic.smax %{{.*}} %{{.*}} %{{.*}} %{{.*}} %{{.*}} : i32
   // CHECK: rocdl.raw.buffer.atomic.umin %{{.*}} %{{.*}} %{{.*}} %{{.*}} %{{.*}} : i32
+  // CHECK: %{{.*}} = rocdl.raw.buffer.atomic.cmpswap(%{{.*}}, %{{.*}}, %{{.*}}, %{{.*}}, %{{.*}}, %{{.*}}) : i32, vector<4xi32>
 
   rocdl.raw.buffer.atomic.smax %vdata1, %rsrc, %offset, %soffset, %aux : i32
   rocdl.raw.buffer.atomic.umin %vdata1, %rsrc, %offset, %soffset, %aux : i32
+  %val = rocdl.raw.buffer.atomic.cmpswap(%vdata1, %vdata1, %rsrc, %offset, %soffset, %aux) : i32, vector<4xi32>
   llvm.return
 }
 

mlir/test/Target/LLVMIR/rocdl.mlir

@@ -294,6 +294,18 @@ llvm.func @rocdl.raw.buffer.atomic.i32(%rsrc : vector<4xi32>,
   llvm.return
 }
 
+llvm.func @rocdl.raw.buffer.atomic.cmpswap(%rsrc : vector<4xi32>,
+                        %offset : i32, %soffset : i32,
+                        %src : i32, %cmp : i32) -> i32 {
+  %aux = llvm.mlir.constant(0 : i32) : i32
+  // CHECK-LABEL: rocdl.raw.buffer.atomic.cmpswap
+  // CHECK: [[val:%.+]] = call i32 @llvm.amdgcn.raw.buffer.atomic.cmpswap.i32(i32 %{{.*}}, i32 %{{.*}}, <4 x i32> %{{.*}}, i32 %{{.*}}, i32 %{{.*}}, i32 {{.*}}
+  // CHECK: ret i32 [[val]]
+
+  %val = rocdl.raw.buffer.atomic.cmpswap(%src, %cmp, %rsrc, %offset, %soffset, %aux) : i32, vector<4xi32>
+  llvm.return %val : i32
+}
+
 // CHECK-DAG: attributes #[[$KERNEL_ATTRS]] = { "amdgpu-flat-work-group-size"="1,256" "amdgpu-implicitarg-num-bytes"="56" }
 // CHECK-DAG: attributes #[[$KERNEL_WORKGROUP_ATTRS]] = { "amdgpu-flat-work-group-size"="1,1024"
 // CHECK-DAG: attributes #[[$KNOWN_BLOCK_SIZE_ATTRS]] = { "amdgpu-flat-work-group-size"="128,128"