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[X86] Fix arithmetic error in extractVector #128052

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Merged
merged 2 commits into from
Feb 24, 2025
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[X86] Fix arithmetic error in extractVector #128052

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1df623a
[X86] Fix arithmetic error in extractVector
daniel-zabawa Feb 20, 2025
b338971
reduce/rename test and add assertion
daniel-zabawa Feb 21, 2025
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6 changes: 3 additions & 3 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4066,9 +4066,9 @@ static SDValue extractSubVector(SDValue Vec, unsigned IdxVal, SelectionDAG &DAG,
const SDLoc &dl, unsigned vectorWidth) {
EVT VT = Vec.getValueType();
EVT ElVT = VT.getVectorElementType();
unsigned Factor = VT.getSizeInBits() / vectorWidth;
EVT ResultVT = EVT::getVectorVT(*DAG.getContext(), ElVT,
VT.getVectorNumElements() / Factor);
unsigned ResultNumElts =
(VT.getVectorNumElements() * vectorWidth) / VT.getSizeInBits();
EVT ResultVT = EVT::getVectorVT(*DAG.getContext(), ElVT, ResultNumElts);
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Add an assert to make sure its actually working?
assert(ResultVT.getSizeInBits() == vectorWidth && "Illegal subvector extraction")


// Extract the relevant vectorWidth bits. Generate an EXTRACT_SUBVECTOR
unsigned ElemsPerChunk = vectorWidth / ElVT.getSizeInBits();
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30 changes: 30 additions & 0 deletions llvm/test/CodeGen/X86/pr128052.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
; Ensure assertion is not hit when folding concat of two contiguous extract_subvector operations
; from a source with a non-power-of-two vector length.
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I think we may use utils/update_llc_test_checks.py to generate assemble rather than rely on comments.

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Do not use pr128052 as file name. This is used for issue number only.

; RUN: llc -mattr=+avx2 < %s

source_filename = "foo.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
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These are not needed. And add the triple to RUN line, e.g,
; RUN: llc -mtriple=x86_64 -mattr=+avx2 < %s

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Use ; RUN: llc -mtriple=x86_64 -mattr=+avx2 < %s | FileCheck %s and regenerate the checks with update_llc_test_checks


define void @foo(ptr noundef %pDst, ptr noundef %pSrc) {
bb0:
%sptr1 = getelementptr i8, ptr %pSrc, i64 32
%load598 = load <12 x float>, ptr %sptr1, align 1
br label %bb1
bb1:
%sptr0 = getelementptr i8, ptr %pSrc, i64 16
%load617 = load <12 x float>, ptr %sptr0, align 1
%42 = fsub contract <12 x float> %load617, %load598
%43 = shufflevector <12 x float> %42, <12 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
%44 = fsub contract <12 x float> %load617, %load598
%45 = shufflevector <12 x float> %44, <12 x float> poison, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
%46 = fsub contract <12 x float> %load617, %load598
%47 = shufflevector <12 x float> %46, <12 x float> poison, <4 x i32> <i32 8, i32 9, i32 10, i32 11>
%dptr0 = getelementptr i8, ptr %pDst, i64 16
%dptr1 = getelementptr i8, ptr %pDst, i64 32
%dptr2 = getelementptr i8, ptr %pDst, i64 48
store <4 x float> %43, ptr %dptr0, align 1
store <4 x float> %45, ptr %dptr1, align 1
store <4 x float> %47, ptr %dptr2, align 1
ret void
}
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This can probably be simplified further? And don't use numbered variables.