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[VectorCombine] Fix scalarizeExtExtract for big-endian #157962

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Merged
merged 6 commits into from
Sep 15, 2025
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Merged

[VectorCombine] Fix scalarizeExtExtract for big-endian #157962

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1e1ef6c
[VectorCombine] Fix scalarizeExtExtract for big-endian
uyoyo0 Sep 10, 2025
8f8e444
Simplify LShr construction; add AArch64/PowerPC tests
uyoyo0 Sep 12, 2025
75d1625
clang-format; add lit.local.cfg; regenerate checks
uyoyo0 Sep 12, 2025
d4a1421
remove dce pass from tests
uyoyo0 Sep 12, 2025
97ebb99
Merge branch 'main' into vc/be-mapping-scalarize-extextract
RKSimon Sep 14, 2025
fd77ffb
Merge branch 'main' into vc/be-mapping-scalarize-extextract
RKSimon Sep 15, 2025
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10 changes: 8 additions & 2 deletions llvm/lib/Transforms/Vectorize/VectorCombine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2011,12 +2011,18 @@ bool VectorCombine::scalarizeExtExtract(Instruction &I) {
IntegerType::get(SrcTy->getContext(), DL->getTypeSizeInBits(SrcTy)));
uint64_t SrcEltSizeInBits = DL->getTypeSizeInBits(SrcTy->getElementType());
uint64_t EltBitMask = (1ull << SrcEltSizeInBits) - 1;
uint64_t TotalBits = DL->getTypeSizeInBits(SrcTy);
Type *PackedTy = IntegerType::get(SrcTy->getContext(), TotalBits);
Value *Mask = ConstantInt::get(PackedTy, EltBitMask);
for (User *U : Ext->users()) {
auto *Extract = cast<ExtractElementInst>(U);
uint64_t Idx =
cast<ConstantInt>(Extract->getIndexOperand())->getZExtValue();
Value *LShr = Builder.CreateLShr(ScalarV, Idx * SrcEltSizeInBits);
Value *And = Builder.CreateAnd(LShr, EltBitMask);
uint64_t ShiftAmt = DL->isBigEndian()
? (TotalBits - SrcEltSizeInBits - Idx * SrcEltSizeInBits)
: (Idx * SrcEltSizeInBits);
Value *LShr = Builder.CreateLShr(ScalarV, ShiftAmt);
Value *And = Builder.CreateAnd(LShr, Mask);
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clang-format this bit

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Done thanks

U->replaceAllUsesWith(And);
}
return true;
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23 changes: 23 additions & 0 deletions llvm/test/Transforms/VectorCombine/AArch64/scalarize-ext-extract-endian.ll
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@@ -0,0 +1,23 @@
; RUN: opt -passes='vector-combine,dce' -S -mtriple=aarch64-unknown-linux-gnu %s -o - | FileCheck %s --check-prefix=LE
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do you need the dce pass?

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It's not strictly needed but I figured that using dce would make the test output cleaner since the printed IR would only show the bitcast/lshr/and we care about. I don't mind removing it if you prefer to just have vector combine though.

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yes please just show the effects of vectorcombe

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Just made the change thanks

; RUN: opt -passes='vector-combine,dce' -S -mtriple=aarch64_be-unknown-linux-gnu %s -o - | FileCheck %s --check-prefix=BE

define i64 @g(<8 x i8> %v) {
%z = zext <8 x i8> %v to <8 x i64>
%e0 = extractelement <8 x i64> %z, i32 0
%e7 = extractelement <8 x i64> %z, i32 7
%sum = add i64 %e0, %e7
ret i64 %sum
}

; LE-LABEL: @g(
; LE: bitcast <8 x i8> %{{.*}} to i64
; LE: lshr i64 %{{.*}}, 56
; LE: and i64 %{{.*}}, 255
; LE-NOT: extractelement

; BE-LABEL: @g(
; BE: bitcast <8 x i8> %{{.*}} to i64
; BE: and i64 %{{.*}}, 255
; BE: lshr i64 %{{.*}}, 56
; BE-NOT: extractelement

23 changes: 23 additions & 0 deletions llvm/test/Transforms/VectorCombine/PowerPC/scalarize-ext-extract.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
; RUN: opt -passes='vector-combine,dce' -S -mtriple=aarch64-unknown-linux-gnu %s -o - | FileCheck %s --check-prefix=LE
; RUN: opt -passes='vector-combine,dce' -S -mtriple=powerpc64-ibm-aix-xcoff %s -o - | FileCheck %s --check-prefix=BE

define i64 @g(<8 x i8> %v) {
%z = zext <8 x i8> %v to <8 x i64>
%e0 = extractelement <8 x i64> %z, i32 0
%e7 = extractelement <8 x i64> %z, i32 7
%sum = add i64 %e0, %e7
ret i64 %sum
}

; LE-LABEL: @g(
; LE: bitcast <8 x i8> %{{.*}} to i64
; LE: lshr i64 %{{.*}}, 56
; LE: and i64 %{{.*}}, 255
; LE-NOT: extractelement

; BE-LABEL: @g(
; BE: bitcast <8 x i8> %{{.*}} to i64
; BE: and i64 %{{.*}}, 255
; BE: lshr i64 %{{.*}}, 56
; BE-NOT: extractelement

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