Folding extract_strided_metadata input into reinterpret_cast on constant layout #134845
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@llvm/pr-subscribers-mlir-memref @llvm/pr-subscribers-mlir Author: None (ivangarcia44) ChangesWe can always fold the input of a extract_strided_metadata operator to the input of a reinterpret_cast operator, because they point to the same memory. Note that the reinterpret_cast does not use the layout of its input memref, only its base memory pointer which is the same as the base pointer returned by the extract_strided_metadata operator and the base pointer of the extract_strided_metadata memref input. This folding is only profitable when the reinterpret_cast layout is constant, because the extract_strided_metadata gets eliminated by dead code elimination. For non-constant folding we don’t get the extract_strided_metadata node eliminated and one of the LLVM tests regress in performance because the folding gets in the way of another optimization. For this reason, the folding is only done on constant layout. Operations like expand_shape, collapse_shape, and subview are lowered to a pair of extract_strided_metadata and reinterpret_cast like this: %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index %reinterpret_cast = memref.reinterpret_cast %base_buffer to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<f32> to memref<OD1x...xODNxBaseType > In many cases the input of the extract_strided_metadata input can be passed directly into the input of the reinterpret_cast operation like this (see how %base_buffer is replaced by %input_memref in the reinterpret_cast above and the input type is updated): %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index When dealing with static dimensions, the extract_strided_metatdata will become deadcode and we end up only with a reinterpret_cast: %reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType > Note that reinterpret_cast only reads the base memory pointer from the input memref (%input_memref above), which is equivalent to the %base_buffer returned by the extract_strided_metadata operation. Hence it is legal always to use the extract_strided_metadata input memref directly in the reinterpret_cast. Note that since this is a pointer, this operation is legal even when the base pointer values are modified between the operation pair. Full diff: https://github.com/llvm/llvm-project/pull/134845.diff 4 Files Affected:
diff --git a/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td b/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
index 3edc2433c85ea..990a282771502 100644
--- a/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
+++ b/mlir/include/mlir/Dialect/MemRef/IR/MemRefOps.td
@@ -1440,6 +1440,9 @@ def MemRef_ReinterpretCastOp
SmallVector<OpFoldResult> getConstifiedMixedStrides();
/// Similar to `getConstifiedMixedSizes` but for the offset.
OpFoldResult getConstifiedMixedOffset();
+ /// Returns true if the reinterpret cast operation's offset, stride, and
+ /// size are all constant.
+ bool isLayoutConstant();
}];
let hasFolder = 1;
diff --git a/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp b/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
index 123666848f83a..629d0d8d425b1 100644
--- a/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
+++ b/mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
@@ -1124,7 +1124,7 @@ struct DimOfMemRefReshape : public OpRewritePattern<DimOp> {
}
} // else dim.getIndex is a block argument to reshape->getBlock and
// dominates reshape
- } // Check condition 2
+ } // Check condition 2
else if (dim->getBlock() != reshape->getBlock() &&
!dim.getIndex().getParentRegion()->isProperAncestor(
reshape->getParentRegion())) {
@@ -1948,6 +1948,27 @@ OpFoldResult ReinterpretCastOp::fold(FoldAdaptor /*operands*/) {
if (auto prev = src.getDefiningOp<CastOp>())
return prev.getSource();
+ // reinterpret_cast(extract_strided_metadata(x)) -> reinterpret_cast(x).
+ //
+ // We can always fold the input of a extract_strided_metadata operator
+ // to the input of a reinterpret_cast operator, because they point to
+ // the same memory. Note that the reinterpret_cast does not use the
+ // layout of its input memref, only its base memory pointer which is
+ // the same as the base pointer returned by the extract_strided_metadata
+ // operator and the base pointer of the extract_strided_metadata memref
+ // input. This folding is only profitable when the reinterpret_cast
+ // layout is constant, because the extract_strided_metadata gets
+ // eliminated by dead code elimination. For non-constant folding we don’t
+ // get the extract_strided_metadata node eliminated and one of the LLVM
+ // tests regress in performance because the folding gets in the way of
+ // another optimization. For this reason the folding is only done on
+ // constant layout.
+ if (auto prev = src.getDefiningOp<ExtractStridedMetadataOp>()) {
+ if (isLayoutConstant()) {
+ return prev.getSource();
+ }
+ }
+
// reinterpret_cast(subview(x)) -> reinterpret_cast(x) if subview offsets
// are 0.
if (auto prev = src.getDefiningOp<SubViewOp>())
@@ -1973,6 +1994,22 @@ OpFoldResult ReinterpretCastOp::fold(FoldAdaptor /*operands*/) {
return nullptr;
}
+bool ReinterpretCastOp::isLayoutConstant() {
+ if (llvm::all_of(
+ getOffsets(),
+ [](OpFoldResult val) { return isConstantIntValue(val, 0); }) &&
+ llvm::all_of(
+ getStrides(),
+ [](OpFoldResult val) { return isConstantIntValue(val, 0); }) &&
+ llvm::all_of(getSizes(), [](OpFoldResult val) {
+ return isConstantIntValue(val, 0);
+ })) {
+ return true;
+ } else {
+ return false;
+ }
+}
+
SmallVector<OpFoldResult> ReinterpretCastOp::getConstifiedMixedSizes() {
SmallVector<OpFoldResult> values = getMixedSizes();
constifyIndexValues(values, getType(), getContext(), getConstantSizes,
diff --git a/mlir/test/Conversion/MemRefToLLVM/expand-then-convert-to-llvm.mlir b/mlir/test/Conversion/MemRefToLLVM/expand-then-convert-to-llvm.mlir
index fe91d26d5a251..f1cb9c9f165be 100644
--- a/mlir/test/Conversion/MemRefToLLVM/expand-then-convert-to-llvm.mlir
+++ b/mlir/test/Conversion/MemRefToLLVM/expand-then-convert-to-llvm.mlir
@@ -195,10 +195,10 @@ func.func @subview_const_stride(%0 : memref<64x4xf32, strided<[4, 1], offset: 0>
func.func @subview_const_stride_and_offset(%0 : memref<64x8xf32, strided<[8, 1], offset: 0>>) -> memref<62x3xf32, strided<[8, 1], offset: 2>> {
// The last "insertvalue" that populates the memref descriptor from the function arguments.
// CHECK: %[[MEMREF:.*]] = builtin.unrealized_conversion_cast %[[MEM]]
+ // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[BASE:.*]] = llvm.extractvalue %[[MEMREF]][0] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[BASE_ALIGNED:.*]] = llvm.extractvalue %[[MEMREF]][1] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
- // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[BASE_ALIGNED]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[CST_OFF:.*]] = llvm.mlir.constant(2 : index) : i64
@@ -265,11 +265,11 @@ func.func @subview_mixed_static_dynamic(%0 : memref<64x4xf32, strided<[4, 1], of
// CHECK: %[[MEM:.*]]: memref<{{.*}}>,
func.func @subview_leading_operands(%0 : memref<5x3xf32>, %1: memref<5x?xf32>) -> memref<3x3xf32, strided<[3, 1], offset: 6>> {
// CHECK: %[[MEMREF:.*]] = builtin.unrealized_conversion_cast %[[MEM]]
+ // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// Alloc ptr
// CHECK: %[[BASE:.*]] = llvm.extractvalue %[[MEMREF]][0] : !llvm.struct<(ptr, ptr, i64
// Aligned ptr
// CHECK: %[[BASE_ALIGNED:.*]] = llvm.extractvalue %[[MEMREF]][1] : !llvm.struct<(ptr, ptr, i64
- // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[BASE_ALIGNED]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// Offset
@@ -331,9 +331,9 @@ func.func @subview_leading_operands_dynamic(%0 : memref<5x?xf32>) -> memref<3x?x
// CHECK: %[[MEM:.*]]: memref
func.func @subview_rank_reducing_leading_operands(%0 : memref<5x3xf32>) -> memref<3xf32, strided<[1], offset: 3>> {
// CHECK: %[[MEMREF:.*]] = builtin.unrealized_conversion_cast %[[MEM]]
+ // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// CHECK: %[[BASE:.*]] = llvm.extractvalue %[[MEMREF]][0] : !llvm.struct<(ptr, ptr, i64
// CHECK: %[[BASE_ALIGNED:.*]] = llvm.extractvalue %[[MEMREF]][1] : !llvm.struct<(ptr, ptr, i64
- // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// Alloc ptr
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// Aligned ptr
@@ -356,9 +356,9 @@ func.func @subview_rank_reducing_leading_operands(%0 : memref<5x3xf32>) -> memre
// CHECK-SAME: (%[[MEM:.*]]: memref<7xf32>)
func.func @subview_negative_stride(%arg0 : memref<7xf32>) -> memref<7xf32, strided<[-1], offset: 6>> {
// CHECK: %[[MEMREF:.*]] = builtin.unrealized_conversion_cast %[[MEM]]
+ // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// CHECK: %[[BASE:.*]] = llvm.extractvalue %[[MEMREF]][0] : !llvm.struct<(ptr, ptr, i64
// CHECK: %[[BASE_ALIGNED:.*]] = llvm.extractvalue %[[MEMREF]][1] : !llvm.struct<(ptr, ptr, i64
- // CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[BASE_ALIGNED]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<1 x i64>, array<1 x i64>)>
// CHECK: %[[CST_OFF0:.*]] = llvm.mlir.constant(6 : index) : i64
@@ -384,12 +384,12 @@ func.func @collapse_shape_static(%arg0: memref<1x3x4x1x5xf32>) -> memref<3x4x5xf
// CHECK-LABEL: func @collapse_shape_static
// CHECK-SAME: %[[ARG:.*]]: memref<1x3x4x1x5xf32>) -> memref<3x4x5xf32> {
// CHECK: %[[MEM:.*]] = builtin.unrealized_conversion_cast %[[ARG]] : memref<1x3x4x1x5xf32> to !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
+// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
// CHECK: %[[BASE_BUFFER:.*]] = llvm.extractvalue %[[MEM]][0] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
// CHECK: %[[ALIGNED_BUFFER:.*]] = llvm.extractvalue %[[MEM]][1] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
-// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
-// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE_BUFFER]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[ALIGNED_BUFFER]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
+// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
// CHECK: %[[DESC2:.*]] = llvm.insertvalue %[[C0]], %[[DESC1]][2] : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
// CHECK: %[[C3:.*]] = llvm.mlir.constant(3 : index) : i64
// CHECK: %[[DESC3:.*]] = llvm.insertvalue %[[C3]], %[[DESC2]][3, 0] : !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
@@ -458,12 +458,12 @@ func.func @expand_shape_static(%arg0: memref<3x4x5xf32>) -> memref<1x3x4x1x5xf32
// CHECK-LABEL: func @expand_shape_static
// CHECK-SAME: %[[ARG:.*]]: memref<3x4x5xf32>) -> memref<1x3x4x1x5xf32> {
// CHECK: %[[MEM:.*]] = builtin.unrealized_conversion_cast %[[ARG]] : memref<3x4x5xf32> to !llvm.struct<(ptr, ptr, i64, array<3 x i64>, array<3 x i64>)>
+// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
// CHECK: %[[BASE_BUFFER:.*]] = llvm.extractvalue %[[MEM]][0] : !llvm.struct<(ptr, ptr, i64,
// CHECK: %[[ALIGNED_BUFFER:.*]] = llvm.extractvalue %[[MEM]][1] : !llvm.struct<(ptr, ptr, i64,
-// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
-// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE_BUFFER]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[ALIGNED_BUFFER]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
+// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
// CHECK: %[[DESC2:.*]] = llvm.insertvalue %[[C0]], %[[DESC1]][2] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
// CHECK: %[[C1:.*]] = llvm.mlir.constant(1 : index) : i64
// CHECK: %[[DESC3:.*]] = llvm.insertvalue %[[C1]], %[[DESC2]][3, 0] : !llvm.struct<(ptr, ptr, i64, array<5 x i64>, array<5 x i64>)>
@@ -494,9 +494,9 @@ func.func @collapse_shape_fold_zero_dim(%arg0 : memref<1x1xf32>) -> memref<f32>
// CHECK-LABEL: func.func @collapse_shape_fold_zero_dim(
// CHECK-SAME: %[[ARG:.*]]: memref<1x1xf32>) -> memref<f32> {
// CHECK: %[[MEM:.*]] = builtin.unrealized_conversion_cast %[[ARG]] : memref<1x1xf32> to !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
+// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64)>
// CHECK: %[[BASE_BUFFER:.*]] = llvm.extractvalue %[[MEM]][0] : !llvm.struct<(ptr, ptr, i64,
// CHECK: %[[ALIGNED_BUFFER:.*]] = llvm.extractvalue %[[MEM]][1] : !llvm.struct<(ptr, ptr, i64,
-// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE_BUFFER]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[ALIGNED_BUFFER]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64)>
// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
@@ -515,12 +515,12 @@ func.func @expand_shape_zero_dim(%arg0 : memref<f32>) -> memref<1x1xf32> {
// CHECK-LABEL: func.func @expand_shape_zero_dim(
// CHECK-SAME: %[[ARG:.*]]: memref<f32>) -> memref<1x1xf32> {
// CHECK: %[[MEM:.*]] = builtin.unrealized_conversion_cast %[[ARG]] : memref<f32> to !llvm.struct<(ptr, ptr, i64)>
+// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[BASE_BUFFER:.*]] = llvm.extractvalue %[[MEM]][0] : !llvm.struct<(ptr, ptr, i64)>
// CHECK: %[[ALIGNED_BUFFER:.*]] = llvm.extractvalue %[[MEM]][1] : !llvm.struct<(ptr, ptr, i64)>
-// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
-// CHECK: %[[DESC:.*]] = llvm.mlir.poison : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC0:.*]] = llvm.insertvalue %[[BASE_BUFFER]], %[[DESC]][0] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[DESC1:.*]] = llvm.insertvalue %[[ALIGNED_BUFFER]], %[[DESC0]][1] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
+// CHECK: %[[C0:.*]] = llvm.mlir.constant(0 : index) : i64
// CHECK: %[[DESC2:.*]] = llvm.insertvalue %[[C0]], %[[DESC1]][2] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
// CHECK: %[[C1:.*]] = llvm.mlir.constant(1 : index) : i64
// CHECK: %[[DESC3:.*]] = llvm.insertvalue %[[C1]], %[[DESC2]][3, 0] : !llvm.struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)>
diff --git a/mlir/test/Dialect/MemRef/expand-strided-metadata.mlir b/mlir/test/Dialect/MemRef/expand-strided-metadata.mlir
index 1e6b0111fa4c7..da74c73ccd7a5 100644
--- a/mlir/test/Dialect/MemRef/expand-strided-metadata.mlir
+++ b/mlir/test/Dialect/MemRef/expand-strided-metadata.mlir
@@ -975,11 +975,7 @@ func.func @simplify_collapse(%arg : memref<?x?x4x?x6x7xi32>)
//
// CHECK-LABEL: func @simplify_collapse_with_dim_of_size1(
// CHECK-SAME: %[[ARG:.*]]: memref<3x1xf32, strided<[2, 1]>>,
-//
-// CHECK: %[[BASE:.*]], %[[OFFSET:.*]], %[[SIZES:.*]]:2, %[[STRIDES:.*]]:2 = memref.extract_strided_metadata %[[ARG]] : memref<3x1xf32, strided<[2, 1]>>
-//
-//
-// CHECK: %[[COLLAPSE_VIEW:.*]] = memref.reinterpret_cast %[[BASE]] to offset: [0], sizes: [3], strides: [2]
+// CHECK: %[[COLLAPSE_VIEW:.*]] = memref.reinterpret_cast %[[ARG]] to offset: [0], sizes: [3], strides: [2]
func.func @simplify_collapse_with_dim_of_size1(%arg0: memref<3x1xf32, strided<[2,1]>>, %arg1: memref<3xf32>) {
%collapse_shape = memref.collapse_shape %arg0 [[0, 1]] :
|
joker-eph
reviewed
Apr 8, 2025
matthias-springer
approved these changes
Apr 9, 2025
|
@ivangarcia44 Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR. Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues. How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
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…4845) We can always fold the input of a extract_strided_metadata operator to the input of a reinterpret_cast operator, because they point to the same memory. Note that the reinterpret_cast does not use the layout of its input memref, only its base memory pointer which is the same as the base pointer returned by the extract_strided_metadata operator and the base pointer of the extract_strided_metadata memref input. Operations like expand_shape, collapse_shape, and subview are lowered to a pair of extract_strided_metadata and reinterpret_cast like this: %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index %reinterpret_cast = memref.reinterpret_cast %base_buffer to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<f32> to memref<OD1x...xODNxBaseType > In many cases the input of the extract_strided_metadata input can be passed directly into the input of the reinterpret_cast operation like this (see how %base_buffer is replaced by %input_memref in the reinterpret_cast above and the input type is updated): %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index %reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType > When dealing with static dimensions, the extract_strided_metatdata will become deadcode and we end up only with a reinterpret_cast: %reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType > Note that reinterpret_cast only reads the base memory pointer from the input memref (%input_memref above), which is equivalent to the %base_buffer returned by the extract_strided_metadata operation. Hence it is legal always to use the extract_strided_metadata input memref directly in the reinterpret_cast. Note that since this is a pointer, this operation is legal even when the base pointer values are modified between the operation pair. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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…4845) We can always fold the input of a extract_strided_metadata operator to the input of a reinterpret_cast operator, because they point to the same memory. Note that the reinterpret_cast does not use the layout of its input memref, only its base memory pointer which is the same as the base pointer returned by the extract_strided_metadata operator and the base pointer of the extract_strided_metadata memref input. Operations like expand_shape, collapse_shape, and subview are lowered to a pair of extract_strided_metadata and reinterpret_cast like this: %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index %reinterpret_cast = memref.reinterpret_cast %base_buffer to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<f32> to memref<OD1x...xODNxBaseType > In many cases the input of the extract_strided_metadata input can be passed directly into the input of the reinterpret_cast operation like this (see how %base_buffer is replaced by %input_memref in the reinterpret_cast above and the input type is updated): %base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref<f32>, index, index, index, index, index %reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType > When dealing with static dimensions, the extract_strided_metatdata will become deadcode and we end up only with a reinterpret_cast: %reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType > Note that reinterpret_cast only reads the base memory pointer from the input memref (%input_memref above), which is equivalent to the %base_buffer returned by the extract_strided_metadata operation. Hence it is legal always to use the extract_strided_metadata input memref directly in the reinterpret_cast. Note that since this is a pointer, this operation is legal even when the base pointer values are modified between the operation pair. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (#135244) While working on #134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (llvm#135244) While working on llvm#134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (llvm#135244) While working on llvm#134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (llvm#135244) While working on llvm#134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (llvm#135244) While working on llvm#134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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… behavior in relation to their input memref underlying memory and view (llvm#135244) While working on llvm#134845 I was trying to understand the difference of how the reinterpret_cast and subview operators see the input memref, but it was not clear to me. I did a couple of experiments in which I learned that the subview takes into account the view of the input memref to create the view of the output memref, while the reinterpret_cast just uses the underlying memory of the input memref. I thought it would help future readers to see these two experiements as examples in the documentation to quickly figure out the difference between these two operators. @matthias-springer @joker-eph @sahas3 @Hanumanth04 @dixinzhou @rafaelubalmw --------- Co-authored-by: Ivan Garcia <[email protected]>
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We can always fold the input of a extract_strided_metadata operator to the input of a reinterpret_cast operator, because they point to the same memory. Note that the reinterpret_cast does not use the layout of its input memref, only its base memory pointer which is the same as the base pointer returned by the extract_strided_metadata operator and the base pointer of the extract_strided_metadata memref input.
Operations like expand_shape, collapse_shape, and subview are lowered to a pair of extract_strided_metadata and reinterpret_cast like this:
%base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref, index, index, index, index, index
%reinterpret_cast = memref.reinterpret_cast %base_buffer to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref to memref<OD1x...xODNxBaseType >
In many cases the input of the extract_strided_metadata input can be passed directly into the input of the reinterpret_cast operation like this (see how %base_buffer is replaced by %input_memref in the reinterpret_cast above and the input type is updated):
%base_buffer, %offset, %sizes:2, %strides:2 = memref.extract_strided_metadata %input_memref : memref<ID1x...xIDNxBaseType> -> memref, index, index, index, index, index
%reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType >
When dealing with static dimensions, the extract_strided_metatdata will become deadcode and we end up only with a reinterpret_cast:
%reinterpret_cast = memref.reinterpret_cast %input_memref to offset: [%o1], sizes: [%d1,...,%dN], strides: [%s1,...,%N] : memref<ID1x...xIDNxBaseType> to memref<OD1x...xODNxBaseType >
Note that reinterpret_cast only reads the base memory pointer from the input memref (%input_memref above), which is equivalent to the %base_buffer returned by the extract_strided_metadata operation. Hence it is legal always to use the extract_strided_metadata input memref directly in the reinterpret_cast. Note that since this is a pointer, this operation is legal even when the base pointer values are modified between the operation pair.
@matthias-springer
@joker-eph
@sahas3
@Hanumanth04
@dixinzhou
@rafaelubalmw