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[mlir][Vector] Teach how to materialize UB constant to Vector #125596

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Merged
merged 2 commits into from
Feb 4, 2025
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[mlir][Vector] Teach how to materialize UB constant to Vector #125596

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[mlir][Vector] Teach Vector to materialize UB constant
dcaballe Feb 3, 2025
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dcaballe Feb 4, 2025
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19 changes: 3 additions & 16 deletions mlir/lib/Dialect/Vector/IR/VectorOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -437,6 +437,9 @@ void VectorDialect::initialize() {
Operation *VectorDialect::materializeConstant(OpBuilder &builder,
Attribute value, Type type,
Location loc) {
if (isa<ub::PoisonAttrInterface>(value))
return value.getDialect().materializeConstant(builder, value, type, loc);

return arith::ConstantOp::materialize(builder, value, type, loc);
}

Expand Down Expand Up @@ -2273,20 +2276,6 @@ LogicalResult foldExtractFromFromElements(ExtractOp extractOp,
return success();
}

/// Fold an insert or extract operation into an poison value when a poison index
/// is found at any dimension of the static position.
template <typename OpTy>
LogicalResult
canonicalizePoisonIndexInsertExtractOp(OpTy op, PatternRewriter &rewriter) {
if (auto poisonAttr = foldPoisonIndexInsertExtractOp(
op.getContext(), op.getStaticPosition(), OpTy::kPoisonIndex)) {
rewriter.replaceOpWithNewOp<ub::PoisonOp>(op, op.getType(), poisonAttr);
return success();
}

return failure();
}

} // namespace

void ExtractOp::getCanonicalizationPatterns(RewritePatternSet &results,
Expand All @@ -2295,7 +2284,6 @@ void ExtractOp::getCanonicalizationPatterns(RewritePatternSet &results,
ExtractOpFromBroadcast, ExtractOpFromCreateMask>(context);
results.add(foldExtractFromShapeCastToShapeCast);
results.add(foldExtractFromFromElements);
results.add(canonicalizePoisonIndexInsertExtractOp<ExtractOp>);
}

static void populateFromInt64AttrArray(ArrayAttr arrayAttr,
Expand Down Expand Up @@ -3068,7 +3056,6 @@ void InsertOp::getCanonicalizationPatterns(RewritePatternSet &results,
MLIRContext *context) {
results.add<InsertToBroadcast, BroadcastFolder, InsertSplatToSplat,
InsertOpConstantFolder>(context);
results.add(canonicalizePoisonIndexInsertExtractOp<InsertOp>);
}

OpFoldResult vector::InsertOp::fold(FoldAdaptor adaptor) {
Expand Down
18 changes: 14 additions & 4 deletions mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir
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Expand Up @@ -1250,13 +1250,13 @@ func.func @extract_scalar_from_vec_1d_f32(%arg0: vector<16xf32>) -> f32 {

// -----

func.func @extract_poison_idx(%arg0: vector<16xf32>) -> f32 {
func.func @extract_scalar_from_vec_1d_f32_poison_idx(%arg0: vector<16xf32>) -> f32 {
%0 = vector.extract %arg0[-1]: f32 from vector<16xf32>
return %0 : f32
}
// CHECK-LABEL: @extract_poison_idx
// CHECK: %[[IDX:.*]] = llvm.mlir.constant(-1 : i64) : i64
// CHECK: llvm.extractelement {{.*}}[%[[IDX]] : i64] : vector<16xf32>
// CHECK-LABEL: @extract_scalar_from_vec_1d_f32_poison_idx
// CHECK: %[[UB:.*]] = ub.poison : f32
// CHECK: return %[[UB]] : f32
Comment on lines +1258 to +1259
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Could you use this opportunity and rename:

  • @extract_poison_idx, as
  • @extract_scalar_from_vec_1d_f32_poison_idx

This way we would maintain consistent naming.

Also, is there a test with poison idx when extracting form something rank > 1?


// -----

Expand Down Expand Up @@ -1335,6 +1335,16 @@ func.func @extract_vec_2d_from_vec_3d_f32(%arg0: vector<4x3x16xf32>) -> vector<3

// -----

func.func @extract_vec_2d_from_vec_3d_f32_poison_idx(%arg0: vector<4x3x16xf32>) -> vector<3x16xf32> {
%0 = vector.extract %arg0[-1]: vector<3x16xf32> from vector<4x3x16xf32>
return %0 : vector<3x16xf32>
}
// CHECK-LABEL: @extract_vec_2d_from_vec_3d_f32_poison_idx
// CHECK: %[[UB:.*]] = ub.poison : vector<3x16xf32>
// CHECK: return %[[UB]] : vector<3x16xf32>

// -----

func.func @extract_vec_2d_from_vec_3d_f32_scalable(%arg0: vector<4x3x[16]xf32>) -> vector<3x[16]xf32> {
%0 = vector.extract %arg0[0]: vector<3x[16]xf32> from vector<4x3x[16]xf32>
return %0 : vector<3x[16]xf32>
Expand Down