[Matrix] Optimize shuffle extracts with ShapeInfo #142276
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When a shuffle extracts a vector that we have as part of the ShapeInfo for a Matrix (i.e. one column of a column-major matrix, or one row of a row-major matrix), replace the shuffle with that vector during lowering.
jroelofs
commented
May 31, 2025
| %inv = call <9 x double> @llvm.matrix.column.major.load(ptr %in, i64 3, i1 1, i32 3, i32 3) | ||
| %row = shufflevector <9 x double> %inv, <9 x double> poison, <3 x i32> <i32 0, i32 3, i32 6> | ||
| ret <3 x double> %row | ||
| } |
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TODO: needs quite a few more tests.
|
Leaving this as a draft for now. It doesn't seem to help much, I think possibly because instcombine can already do this. |
You can test this locally with the following command:git-clang-format --diff HEAD~1 HEAD --extensions cpp -- llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cppView the diff from clang-format here.diff --git a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
index 93d56a9a7..8ecbb88a3 100644
--- a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
@@ -1354,7 +1354,7 @@ public:
for (int I = 1, E = Mask.size(); I != E; ++I) {
if (Mask[I] == PoisonMaskElem)
return false;
- if (Mask[I-1] + 1 != Mask[I])
+ if (Mask[I - 1] + 1 != Mask[I])
return false;
}
|
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When a shuffle extracts a vector that we have as part of the ShapeInfo for a Matrix (i.e. one column of a column-major matrix, or one row of a row-major matrix), replace the shuffle with that vector during lowering.