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[mlir][tensor] Fix tensor::PackOp fold() handling of padding value #87296

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Apr 2, 2024
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16 changes: 11 additions & 5 deletions mlir/lib/Dialect/Tensor/IR/TensorOps.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1068,10 +1068,13 @@ void EmptyOp::getCanonicalizationPatterns(RewritePatternSet &results,

/// Try to remove a tensor operation if it would only reshape a constant.
/// Removes the op and replaces the constant with a new constant of the result
/// shape.
static OpFoldResult reshapeConstantSource(DenseElementsAttr source,
TensorType result) {
if (source && source.isSplat() && result.hasStaticShape())
/// shape. When an optional cst attribute is passed, it is reshaped only if the
/// splat value matches the value in the attribute.
static OpFoldResult
reshapeConstantSource(DenseElementsAttr source, TensorType result,
std::optional<Attribute> cst = std::nullopt) {
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Please update the documentation for this.

if (source && source.isSplat() && result.hasStaticShape() &&
(!cst.has_value() || source.getSplatValue<Attribute>() == cst.value()))
return source.resizeSplat(result);

return {};
Expand Down Expand Up @@ -4143,9 +4146,12 @@ bool PackOp::isLikePad() {
}

OpFoldResult PackOp::fold(FoldAdaptor adaptor) {
std::optional<Attribute> paddingValue;
if (auto pad = adaptor.getPaddingValue())
paddingValue = pad;
if (OpFoldResult reshapedSource = reshapeConstantSource(
llvm::dyn_cast_if_present<DenseElementsAttr>(adaptor.getSource()),
getResult().getType()))
getDestType(), paddingValue))
return reshapedSource;
return {};
}
Expand Down
33 changes: 33 additions & 0 deletions mlir/test/Dialect/Tensor/canonicalize.mlir
Original file line number Diff line number Diff line change
Expand Up @@ -830,6 +830,39 @@ func.func @fold_pack_constant_splat(%dest : tensor<8x16x8x32xf32>) -> tensor<8x1

// -----

// CHECK-LABEL: func @fold_padding_value_pack_constant_splat
// CHECK-NOT: tensor.pack
// CHECK: arith.constant dense<1.000000e-01> : tensor<8x16x8x32xf32>
func.func @fold_padding_value_pack_constant_splat(%dest : tensor<8x16x8x32xf32>) -> tensor<8x16x8x32xf32> {
%pad = arith.constant 1.000000e-01 : f32
%cst = arith.constant dense<1.000000e-01> : tensor<63x127xf32>
%0 = tensor.pack %cst
padding_value(%pad : f32)
outer_dims_perm = [1, 0] inner_dims_pos = [0, 1]
inner_tiles = [8, 32] into %dest : tensor<63x127xf32> -> tensor<8x16x8x32xf32>
return %0 : tensor<8x16x8x32xf32>
}


// -----

// CHECK-LABEL: func @nofold_padding_value_pack_constant_splat
// CHECK: arith.constant dense<1.000000e-01> : tensor<63x127xf32>
// CHECK: tensor.pack
func.func @nofold_padding_value_pack_constant_splat(%dest : tensor<8x16x8x32xf32>) -> tensor<8x16x8x32xf32> {
%pad = arith.constant 0.0 : f32
%cst = arith.constant dense<1.000000e-01> : tensor<63x127xf32>
%0 = tensor.pack %cst
padding_value(%pad : f32)
outer_dims_perm = [1, 0]
inner_dims_pos = [0, 1]
inner_tiles = [8, 32]
into %dest : tensor<63x127xf32> -> tensor<8x16x8x32xf32>
return %0 : tensor<8x16x8x32xf32>
}

// -----

func.func @fold_padding_value_pack(%arg0: tensor<1200x500000xf32>) -> tensor<31250x1200x16x1xf32> {
%cst = arith.constant 0.000000e+00 : f32
%0 = tensor.empty() : tensor<31250x1200x16x1xf32>
Expand Down