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[mlir][Vector] Move vector.mask canonicalization to folder #140324

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Merged
merged 2 commits into from
May 22, 2025
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[mlir][Vector] Move vector.mask canonicalization to folder #140324

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[mlir][Vector] Move `vector.mask` canonicalization to folders
dcaballe May 17, 2025
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dcaballe May 21, 2025
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1 change: 0 additions & 1 deletion mlir/include/mlir/Dialect/Vector/IR/VectorOps.td
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Original file line number Diff line number Diff line change
Expand Up @@ -2559,7 +2559,6 @@ def Vector_MaskOp : Vector_Op<"mask", [
Location loc);
}];

let hasCanonicalizer = 1;
let hasFolder = 1;
let hasCustomAssemblyFormat = 1;
let hasVerifier = 1;
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66 changes: 31 additions & 35 deletions mlir/lib/Dialect/Vector/IR/VectorOps.cpp
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Expand Up @@ -6646,13 +6646,40 @@ LogicalResult MaskOp::verify() {
return success();
}

/// Folds vector.mask ops with an all-true mask.
/// Folds empty `vector.mask` with no passthru operand and with or without
/// return values. For example:
///
/// %0 = vector.mask %mask { vector.yield %a : vector<8xf32> } :
/// vector<8xi1> -> vector<8xf32>
/// %1 = user_op %0 : vector<8xf32>
///
/// becomes:
///
/// %0 = user_op %a : vector<8xf32>
///
static LogicalResult foldEmptyMaskOp(MaskOp maskOp, MaskOp::FoldAdaptor adaptor,
SmallVectorImpl<OpFoldResult> &results) {
if (!maskOp.isEmpty() || maskOp.hasPassthru())
return failure();

Block *block = maskOp.getMaskBlock();
auto terminator = cast<vector::YieldOp>(block->front());
if (terminator.getNumOperands() == 0) {
// `vector.mask` has no results, just remove the `vector.mask`.
return success();
}

// `vector.mask` has results, propagate the results.
llvm::append_range(results, terminator.getOperands());
return success();
}

LogicalResult MaskOp::fold(FoldAdaptor adaptor,
SmallVectorImpl<OpFoldResult> &results) {
MaskFormat maskFormat = getMaskFormat(getMask());
if (isEmpty())
return failure();
if (succeeded(foldEmptyMaskOp(*this, adaptor, results)))
return success();

MaskFormat maskFormat = getMaskFormat(getMask());
if (maskFormat != MaskFormat::AllTrue)
return failure();

Expand All @@ -6665,37 +6692,6 @@ LogicalResult MaskOp::fold(FoldAdaptor adaptor,
return success();
}

// Elides empty vector.mask operations with or without return values. Propagates
// the yielded values by the vector.yield terminator, if any, or erases the op,
// otherwise.
class ElideEmptyMaskOp : public OpRewritePattern<MaskOp> {
using OpRewritePattern::OpRewritePattern;

LogicalResult matchAndRewrite(MaskOp maskOp,
PatternRewriter &rewriter) const override {
auto maskingOp = cast<MaskingOpInterface>(maskOp.getOperation());
if (maskingOp.getMaskableOp())
return failure();

if (!maskOp.isEmpty())
return failure();

Block *block = maskOp.getMaskBlock();
auto terminator = cast<vector::YieldOp>(block->front());
if (terminator.getNumOperands() == 0)
rewriter.eraseOp(maskOp);
else
rewriter.replaceOp(maskOp, terminator.getOperands());

return success();
}
};

void MaskOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results.add<ElideEmptyMaskOp>(context);
}

// MaskingOpInterface definitions.

/// Returns the operation masked by this 'vector.mask'.
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6 changes: 4 additions & 2 deletions mlir/test/Conversion/GPUCommon/lower-vector.mlir
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@@ -1,10 +1,12 @@
// RUN: mlir-opt %s --gpu-to-llvm | FileCheck %s

module {
// CHECK-LABEL: func @func
// CHECK-SAME: %[[IN:.*]]: vector<11xf32>
func.func @func(%arg: vector<11xf32>) -> vector<11xf32> {
%cst_41 = arith.constant dense<true> : vector<11xi1>
// CHECK: vector.mask
// CHECK-SAME: vector.yield %arg0
// CHECK-NOT: vector.mask
// CHECK: return %[[IN]] : vector<11xf32>
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Not sure what the intent of this test is but I'm updating it accordingly

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This is a regression test originally added in 6904998 . It’s a great example of why "regression" on its own isn’t a helpful test description 😅

That commit fixed a bug in ConvertVectorToLLVM.cpp - it’s unclear why the test landed under the "GPUCommon" subdirectory. Unfortunately, with no comments and uninformative function/variable names, it’s hard to tell what specific edge case this was meant to cover - which makes changes like this unnecessarily tricky to review.

From the context of the original commit, it seems the intent was to test the lowering of empty vector.mask. If so, I think this would be better placed in: mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir

WDYT? Would you mind moving it there instead?

Also - if I’ve understood the original intent correctly, your update here makes sense 🙂

%127 = vector.mask %cst_41 { vector.yield %arg : vector<11xf32> } : vector<11xi1> -> vector<11xf32>
return %127 : vector<11xf32>
}
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