[Mlir-commits] [mlir] [mlir][vector] Decouple unrolling gather and gather to llvm lowering (PR #132206)
Kunwar Grover
llvmlistbot at llvm.org
Thu Mar 20 06:35:33 PDT 2025
https://github.com/Groverkss created https://github.com/llvm/llvm-project/pull/132206
This patch decouples unrolling vector.gather and lowering vector.gather to llvm.masked.gather.
This is consistent with how vector.load, vector.store, vector.maskedload, vector.maskedstore lower to LLVM.
Some interesting test changes from this patch:
- 2D vector.gather lowering to llvm tests are deleted. This is consistent with other memory load/store ops.
- There are still tests for 2D vector.gather, but the constant mask for these test is modified. This is because with the updated lowering, one of the unrolled vector.gather disappears because it is masked off (also demonstrating why this is a better lowering path)
Overall, this makes vector.gather take the same consistent path for lowering to LLVM as other load/store ops.
>From bba9af20afac5e39c5cdb08c0685d4723450b926 Mon Sep 17 00:00:00 2001
From: Kunwar Grover <groverkss at gmail.com>
Date: Thu, 20 Mar 2025 13:27:56 +0000
Subject: [PATCH] [mlir][vector] Decouple unrolling gather and gather to llvm
lowering
---
.../Vector/Transforms/LoweringPatterns.h | 8 +++-
.../VectorToLLVM/ConvertVectorToLLVM.cpp | 45 ++++++------------
.../VectorToLLVM/ConvertVectorToLLVMPass.cpp | 1 +
.../Vector/Transforms/LowerVectorGather.cpp | 18 +++++---
.../vector-to-llvm-interface.mlir | 46 -------------------
.../VectorToLLVM/vector-to-llvm.mlir | 4 +-
.../Dialect/Vector/TestVectorTransforms.cpp | 1 +
7 files changed, 36 insertions(+), 87 deletions(-)
diff --git a/mlir/include/mlir/Dialect/Vector/Transforms/LoweringPatterns.h b/mlir/include/mlir/Dialect/Vector/Transforms/LoweringPatterns.h
index 601a65333d026..77d8b82b2bad0 100644
--- a/mlir/include/mlir/Dialect/Vector/Transforms/LoweringPatterns.h
+++ b/mlir/include/mlir/Dialect/Vector/Transforms/LoweringPatterns.h
@@ -244,13 +244,17 @@ void populateVectorStepLoweringPatterns(RewritePatternSet &patterns,
/// [FlattenGather]
/// Flattens 2 or more dimensional `vector.gather` ops by unrolling the
/// outermost dimension.
+void populateVectorGatherLoweringPatterns(RewritePatternSet &patterns,
+ PatternBenefit benefit = 1);
+
+/// Populate the pattern set with the following patterns:
///
/// [Gather1DToConditionalLoads]
/// Turns 1-d `vector.gather` into a scalarized sequence of `vector.loads` or
/// `tensor.extract`s. To avoid out-of-bounds memory accesses, these
/// loads/extracts are made conditional using `scf.if` ops.
-void populateVectorGatherLoweringPatterns(RewritePatternSet &patterns,
- PatternBenefit benefit = 1);
+void populateVectorGatherToConditionalLoadPatterns(RewritePatternSet &patterns,
+ PatternBenefit benefit = 1);
/// Populates instances of `MaskOpRewritePattern` to lower masked operations
/// with `vector.mask`. Patterns should rewrite the `vector.mask` operation and
diff --git a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
index 94efec61a466c..148c2ae26be35 100644
--- a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
+++ b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
@@ -269,6 +269,10 @@ class VectorGatherOpConversion
if (failed(isMemRefTypeSupported(memRefType, *this->getTypeConverter())))
return failure();
+ VectorType vType = gather.getVectorType();
+ if (vType.getRank() > 1)
+ return failure();
+
auto loc = gather->getLoc();
// Resolve alignment.
@@ -276,42 +280,21 @@ class VectorGatherOpConversion
if (failed(getMemRefAlignment(*getTypeConverter(), memRefType, align)))
return failure();
+ // Resolve address.
Value ptr = getStridedElementPtr(loc, memRefType, adaptor.getBase(),
adaptor.getIndices(), rewriter);
Value base = adaptor.getBase();
- auto llvmNDVectorTy = adaptor.getIndexVec().getType();
// Handle the simple case of 1-D vector.
- if (!isa<LLVM::LLVMArrayType>(llvmNDVectorTy)) {
- auto vType = gather.getVectorType();
- // Resolve address.
- Value ptrs =
- getIndexedPtrs(rewriter, loc, *this->getTypeConverter(), memRefType,
- base, ptr, adaptor.getIndexVec(), vType);
- // Replace with the gather intrinsic.
- rewriter.replaceOpWithNewOp<LLVM::masked_gather>(
- gather, typeConverter->convertType(vType), ptrs, adaptor.getMask(),
- adaptor.getPassThru(), rewriter.getI32IntegerAttr(align));
- return success();
- }
-
- const LLVMTypeConverter &typeConverter = *this->getTypeConverter();
- auto callback = [align, memRefType, base, ptr, loc, &rewriter,
- &typeConverter](Type llvm1DVectorTy,
- ValueRange vectorOperands) {
- // Resolve address.
- Value ptrs = getIndexedPtrs(
- rewriter, loc, typeConverter, memRefType, base, ptr,
- /*index=*/vectorOperands[0], cast<VectorType>(llvm1DVectorTy));
- // Create the gather intrinsic.
- return rewriter.create<LLVM::masked_gather>(
- loc, llvm1DVectorTy, ptrs, /*mask=*/vectorOperands[1],
- /*passThru=*/vectorOperands[2], rewriter.getI32IntegerAttr(align));
- };
- SmallVector<Value> vectorOperands = {
- adaptor.getIndexVec(), adaptor.getMask(), adaptor.getPassThru()};
- return LLVM::detail::handleMultidimensionalVectors(
- gather, vectorOperands, *getTypeConverter(), callback, rewriter);
+ // Resolve address.
+ Value ptrs =
+ getIndexedPtrs(rewriter, loc, *this->getTypeConverter(), memRefType,
+ base, ptr, adaptor.getIndexVec(), vType);
+ // Replace with the gather intrinsic.
+ rewriter.replaceOpWithNewOp<LLVM::masked_gather>(
+ gather, typeConverter->convertType(vType), ptrs, adaptor.getMask(),
+ adaptor.getPassThru(), rewriter.getI32IntegerAttr(align));
+ return success();
}
};
diff --git a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVMPass.cpp b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVMPass.cpp
index eb1555df5d574..7082b92c95d1d 100644
--- a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVMPass.cpp
+++ b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVMPass.cpp
@@ -81,6 +81,7 @@ void ConvertVectorToLLVMPass::runOnOperation() {
populateVectorInsertExtractStridedSliceTransforms(patterns);
populateVectorStepLoweringPatterns(patterns);
populateVectorRankReducingFMAPattern(patterns);
+ populateVectorGatherLoweringPatterns(patterns);
(void)applyPatternsGreedily(getOperation(), std::move(patterns));
}
diff --git a/mlir/lib/Dialect/Vector/Transforms/LowerVectorGather.cpp b/mlir/lib/Dialect/Vector/Transforms/LowerVectorGather.cpp
index 3b38505becd18..eff8ee0e9de7a 100644
--- a/mlir/lib/Dialect/Vector/Transforms/LowerVectorGather.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/LowerVectorGather.cpp
@@ -38,7 +38,7 @@ using namespace mlir;
using namespace mlir::vector;
namespace {
-/// Flattens 2 or more dimensional `vector.gather` ops by unrolling the
+/// Unrolls 2 or more dimensional `vector.gather` ops by unrolling the
/// outermost dimension. For example:
/// ```
/// %g = vector.gather %base[%c0][%v], %mask, %pass_thru :
@@ -56,14 +56,14 @@ namespace {
/// When applied exhaustively, this will produce a sequence of 1-d gather ops.
///
/// Supports vector types with a fixed leading dimension.
-struct FlattenGather : OpRewritePattern<vector::GatherOp> {
+struct UnrollGather : OpRewritePattern<vector::GatherOp> {
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(vector::GatherOp op,
PatternRewriter &rewriter) const override {
VectorType resultTy = op.getType();
if (resultTy.getRank() < 2)
- return rewriter.notifyMatchFailure(op, "already flat");
+ return rewriter.notifyMatchFailure(op, "already 1-D");
// Unrolling doesn't take vscale into account. Pattern is disabled for
// vectors with leading scalable dim(s).
@@ -107,7 +107,8 @@ struct FlattenGather : OpRewritePattern<vector::GatherOp> {
/// ```mlir
/// %subview = memref.subview %M (...)
/// : memref<100x3xf32> to memref<100xf32, strided<[3]>>
-/// %gather = vector.gather %subview[%idxs] (...) : memref<100xf32, strided<[3]>>
+/// %gather = vector.gather %subview[%idxs] (...) : memref<100xf32,
+/// strided<[3]>>
/// ```
/// ==>
/// ```mlir
@@ -269,6 +270,11 @@ struct Gather1DToConditionalLoads : OpRewritePattern<vector::GatherOp> {
void mlir::vector::populateVectorGatherLoweringPatterns(
RewritePatternSet &patterns, PatternBenefit benefit) {
- patterns.add<FlattenGather, RemoveStrideFromGatherSource,
- Gather1DToConditionalLoads>(patterns.getContext(), benefit);
+ patterns.add<UnrollGather>(patterns.getContext(), benefit);
+}
+
+void mlir::vector::populateVectorGatherToConditionalLoadPatterns(
+ RewritePatternSet &patterns, PatternBenefit benefit) {
+ patterns.add<RemoveStrideFromGatherSource, Gather1DToConditionalLoads>(
+ patterns.getContext(), benefit);
}
diff --git a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
index c3f06dd4d5dd1..44b4a25a051f1 100644
--- a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
+++ b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
@@ -2074,52 +2074,6 @@ func.func @gather_index_scalable(%arg0: memref<?xindex>, %arg1: vector<[3]xindex
// -----
-func.func @gather_2d_from_1d(%arg0: memref<?xf32>, %arg1: vector<2x3xi32>, %arg2: vector<2x3xi1>, %arg3: vector<2x3xf32>) -> vector<2x3xf32> {
- %0 = arith.constant 0: index
- %1 = vector.gather %arg0[%0][%arg1], %arg2, %arg3 : memref<?xf32>, vector<2x3xi32>, vector<2x3xi1>, vector<2x3xf32> into vector<2x3xf32>
- return %1 : vector<2x3xf32>
-}
-
-// CHECK-LABEL: func @gather_2d_from_1d
-// CHECK: %[[B:.*]] = llvm.getelementptr %{{.*}} : (!llvm.ptr, i64) -> !llvm.ptr, f32
-// CHECK: %[[I0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<3xi32>>
-// CHECK: %[[M0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<3xi1>>
-// CHECK: %[[S0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<3xf32>>
-// CHECK: %[[P0:.*]] = llvm.getelementptr %[[B]][%[[I0]]] : (!llvm.ptr, vector<3xi32>) -> !llvm.vec<3 x ptr>, f32
-// CHECK: %[[G0:.*]] = llvm.intr.masked.gather %[[P0]], %[[M0]], %[[S0]] {alignment = 4 : i32} : (!llvm.vec<3 x ptr>, vector<3xi1>, vector<3xf32>) -> vector<3xf32>
-// CHECK: %{{.*}} = llvm.insertvalue %[[G0]], %{{.*}}[0] : !llvm.array<2 x vector<3xf32>>
-// CHECK: %[[I1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<3xi32>>
-// CHECK: %[[M1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<3xi1>>
-// CHECK: %[[S1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<3xf32>>
-// CHECK: %[[P1:.*]] = llvm.getelementptr %[[B]][%[[I1]]] : (!llvm.ptr, vector<3xi32>) -> !llvm.vec<3 x ptr>, f32
-// CHECK: %[[G1:.*]] = llvm.intr.masked.gather %[[P1]], %[[M1]], %[[S1]] {alignment = 4 : i32} : (!llvm.vec<3 x ptr>, vector<3xi1>, vector<3xf32>) -> vector<3xf32>
-// CHECK: %{{.*}} = llvm.insertvalue %[[G1]], %{{.*}}[1] : !llvm.array<2 x vector<3xf32>>
-
-// -----
-
-func.func @gather_2d_from_1d_scalable(%arg0: memref<?xf32>, %arg1: vector<2x[3]xi32>, %arg2: vector<2x[3]xi1>, %arg3: vector<2x[3]xf32>) -> vector<2x[3]xf32> {
- %0 = arith.constant 0: index
- %1 = vector.gather %arg0[%0][%arg1], %arg2, %arg3 : memref<?xf32>, vector<2x[3]xi32>, vector<2x[3]xi1>, vector<2x[3]xf32> into vector<2x[3]xf32>
- return %1 : vector<2x[3]xf32>
-}
-
-// CHECK-LABEL: func @gather_2d_from_1d_scalable
-// CHECK: %[[B:.*]] = llvm.getelementptr %{{.*}} : (!llvm.ptr, i64) -> !llvm.ptr, f32
-// CHECK: %[[I0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<[3]xi32>>
-// CHECK: %[[M0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<[3]xi1>>
-// CHECK: %[[S0:.*]] = llvm.extractvalue %{{.*}}[0] : !llvm.array<2 x vector<[3]xf32>>
-// CHECK: %[[P0:.*]] = llvm.getelementptr %[[B]][%[[I0]]] : (!llvm.ptr, vector<[3]xi32>) -> !llvm.vec<? x 3 x ptr>, f32
-// CHECK: %[[G0:.*]] = llvm.intr.masked.gather %[[P0]], %[[M0]], %[[S0]] {alignment = 4 : i32} : (!llvm.vec<? x 3 x ptr>, vector<[3]xi1>, vector<[3]xf32>) -> vector<[3]xf32>
-// CHECK: %{{.*}} = llvm.insertvalue %[[G0]], %{{.*}}[0] : !llvm.array<2 x vector<[3]xf32>>
-// CHECK: %[[I1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<[3]xi32>>
-// CHECK: %[[M1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<[3]xi1>>
-// CHECK: %[[S1:.*]] = llvm.extractvalue %{{.*}}[1] : !llvm.array<2 x vector<[3]xf32>>
-// CHECK: %[[P1:.*]] = llvm.getelementptr %[[B]][%[[I1]]] : (!llvm.ptr, vector<[3]xi32>) -> !llvm.vec<? x 3 x ptr>, f32
-// CHECK: %[[G1:.*]] = llvm.intr.masked.gather %[[P1]], %[[M1]], %[[S1]] {alignment = 4 : i32} : (!llvm.vec<? x 3 x ptr>, vector<[3]xi1>, vector<[3]xf32>) -> vector<[3]xf32>
-// CHECK: %{{.*}} = llvm.insertvalue %[[G1]], %{{.*}}[1] : !llvm.array<2 x vector<[3]xf32>>
-
-// -----
-
func.func @gather_1d_from_2d(%arg0: memref<4x4xf32>, %arg1: vector<4xi32>, %arg2: vector<4xi1>, %arg3: vector<4xf32>) -> vector<4xf32> {
%0 = arith.constant 3 : index
diff --git a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir
index 1ab28b9df2d19..4a36294b355e7 100644
--- a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir
+++ b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir
@@ -1663,7 +1663,7 @@ func.func @flat_transpose(%arg0: vector<16xf32>) -> vector<16xf32> {
func.func @gather_with_mask(%arg0: memref<?xf32>, %arg1: vector<2x3xi32>, %arg2: vector<2x3xf32>) -> vector<2x3xf32> {
%0 = arith.constant 0: index
- %1 = vector.constant_mask [1, 2] : vector<2x3xi1>
+ %1 = vector.constant_mask [2, 2] : vector<2x3xi1>
%2 = vector.gather %arg0[%0][%arg1], %1, %arg2 : memref<?xf32>, vector<2x3xi32>, vector<2x3xi1>, vector<2x3xf32> into vector<2x3xf32>
return %2 : vector<2x3xf32>
}
@@ -1679,7 +1679,7 @@ func.func @gather_with_mask_scalable(%arg0: memref<?xf32>, %arg1: vector<2x[3]xi
// vector.constant_mask only supports 'none set' or 'all set' scalable
// dimensions, hence [1, 3] rather than [1, 2] as in the example for fixed
// width vectors above.
- %1 = vector.constant_mask [1, 3] : vector<2x[3]xi1>
+ %1 = vector.constant_mask [2, 3] : vector<2x[3]xi1>
%2 = vector.gather %arg0[%0][%arg1], %1, %arg2 : memref<?xf32>, vector<2x[3]xi32>, vector<2x[3]xi1>, vector<2x[3]xf32> into vector<2x[3]xf32>
return %2 : vector<2x[3]xf32>
}
diff --git a/mlir/test/lib/Dialect/Vector/TestVectorTransforms.cpp b/mlir/test/lib/Dialect/Vector/TestVectorTransforms.cpp
index 74838bc0ca2fb..2cf1dde9bd1b8 100644
--- a/mlir/test/lib/Dialect/Vector/TestVectorTransforms.cpp
+++ b/mlir/test/lib/Dialect/Vector/TestVectorTransforms.cpp
@@ -782,6 +782,7 @@ struct TestVectorGatherLowering
void runOnOperation() override {
RewritePatternSet patterns(&getContext());
populateVectorGatherLoweringPatterns(patterns);
+ populateVectorGatherToConditionalLoadPatterns(patterns);
(void)applyPatternsGreedily(getOperation(), std::move(patterns));
}
};
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