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[mlir][vector] shape_cast(constant) -> constant fold for non-splats #145539

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Merged
merged 1 commit into from
Jul 31, 2025
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[mlir][vector] shape_cast(constant) -> constant fold for non-splats #145539

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9 changes: 4 additions & 5 deletions mlir/lib/Dialect/Vector/IR/VectorOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5916,14 +5916,13 @@ OpFoldResult ShapeCastOp::fold(FoldAdaptor adaptor) {
}

// shape_cast(constant) -> constant
if (auto splatAttr =
llvm::dyn_cast_if_present<SplatElementsAttr>(adaptor.getSource()))
return splatAttr.reshape(getType());
if (auto denseAttr =
dyn_cast_if_present<DenseElementsAttr>(adaptor.getSource()))
return denseAttr.reshape(getType());

// shape_cast(poison) -> poison
if (llvm::dyn_cast_if_present<ub::PoisonAttr>(adaptor.getSource())) {
if (llvm::dyn_cast_if_present<ub::PoisonAttr>(adaptor.getSource()))
return ub::PoisonAttr::get(getContext());
}

return {};
}
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34 changes: 32 additions & 2 deletions mlir/test/Dialect/Vector/canonicalize.mlir
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Expand Up @@ -1330,11 +1330,11 @@ func.func @fold_consecutive_broadcasts(%a : i32) -> vector<4x16xi32> {

// -----

// CHECK-LABEL: shape_cast_constant
// CHECK-LABEL: shape_cast_splat_constant
// CHECK-DAG: %[[CST1:.*]] = arith.constant dense<1> : vector<3x4x2xi32>
// CHECK-DAG: %[[CST0:.*]] = arith.constant dense<2.000000e+00> : vector<20x2xf32>
// CHECK: return %[[CST0]], %[[CST1]] : vector<20x2xf32>, vector<3x4x2xi32>
func.func @shape_cast_constant() -> (vector<20x2xf32>, vector<3x4x2xi32>) {
func.func @shape_cast_splat_constant() -> (vector<20x2xf32>, vector<3x4x2xi32>) {
%cst = arith.constant dense<2.000000e+00> : vector<5x4x2xf32>
%cst_1 = arith.constant dense<1> : vector<12x2xi32>
%0 = vector.shape_cast %cst : vector<5x4x2xf32> to vector<20x2xf32>
Expand All @@ -1344,6 +1344,36 @@ func.func @shape_cast_constant() -> (vector<20x2xf32>, vector<3x4x2xi32>) {

// -----

// Test of shape_cast's fold method:
// shape_cast(constant) -> constant.
//
// CHECK-LABEL: @shape_cast_dense_int_constant
// CHECK: %[[CST:.*]] = arith.constant
// CHECK-SAME{LITERAL}: dense<[[2, 3, 5], [7, 11, 13]]>
// CHECK: return %[[CST]] : vector<2x3xi8>
func.func @shape_cast_dense_int_constant() -> vector<2x3xi8> {
%cst = arith.constant dense<[2, 3, 5, 7, 11, 13]> : vector<6xi8>
%0 = vector.shape_cast %cst : vector<6xi8> to vector<2x3xi8>
return %0 : vector<2x3xi8>
}

// -----

// Test of shape_cast fold's method:
// (shape_cast(const_x), const_x) -> (const_x_folded, const_x)
//
// CHECK-LABEL: @shape_cast_dense_float_constant
// CHECK-DAG: %[[CST0:.*]] = {{.*}}1.000000e+00, 2.000000e+00{{.*}} vector<1x2xf32>
// CHECK-DAG: %[[CST1:.*]] = {{.*}}1.000000e+00, 2.000000e+00{{.*}} vector<2xf32>
// CHECK: return %[[CST1]], %[[CST0]] : vector<2xf32>, vector<1x2xf32>
func.func @shape_cast_dense_float_constant() -> (vector<2xf32>, vector<1x2xf32>){
%cst = arith.constant dense<[[1.0, 2.0]]> : vector<1x2xf32>
%0 = vector.shape_cast %cst : vector<1x2xf32> to vector<2xf32>
return %0, %cst : vector<2xf32>, vector<1x2xf32>
}

// -----

// CHECK-LABEL: shape_cast_poison
// CHECK-DAG: %[[CST1:.*]] = ub.poison : vector<3x4x2xi32>
// CHECK-DAG: %[[CST0:.*]] = ub.poison : vector<20x2xf32>
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