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[InstCombine] Add handling for (or (zext x), (shl (zext (ashr x, bw/2-1))), bw/2) -> (sext x) fold #130316

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Merged
merged 3 commits into from
Mar 9, 2025
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[InstCombine] Add handling for (or (zext x), (shl (zext (ashr x, bw/2-1))), bw/2) -> (sext x) fold #130316

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[InstCombine] Add handling for (or (zext x), (shl (zext (ashr x, bw-1…
RKSimon Mar 7, 2025
57792b5
update comments
RKSimon Mar 8, 2025
877723b
Merge branch 'upstream' into ic-sext-split
RKSimon Mar 8, 2025
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7 changes: 3 additions & 4 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3122,13 +3122,12 @@ static Value *matchOrConcat(Instruction &Or, InstCombiner::BuilderTy &Builder) {
// iX ext split: extending or(zext(x),shl(zext(y),bw/2) pattern
// to consume sext/ashr: or(zext(sext(x)),shl(zext(sext(ashr(x))),bw/2)
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Comments need to be updated. BTW, bw/2 should be changed to bw-1.

Value *X;
if (match(LowerSrc, m_SExt(m_Value(X))) &&
if (match(LowerSrc, m_SExtOrSelf(m_Value(X))) &&
match(UpperSrc,
m_SExt(m_AShr(
m_SExtOrSelf(m_AShr(
m_Specific(X),
m_SpecificInt(X->getType()->getScalarSizeInBits() - 1))))) {
m_SpecificInt(X->getType()->getScalarSizeInBits() - 1)))))
return Builder.CreateSExt(X, Ty);
}

return nullptr;
}
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6 changes: 1 addition & 5 deletions llvm/test/Transforms/InstCombine/iX-ext-split.ll
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Expand Up @@ -94,11 +94,7 @@ define void @i128_ext_split_store_i64(i64 %x, ptr %out) {
; CHECK-LABEL: define void @i128_ext_split_store_i64(
; CHECK-SAME: i64 [[X:%.*]], ptr [[OUT:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[LO:%.*]] = zext i64 [[X]] to i128
; CHECK-NEXT: [[SIGN:%.*]] = ashr i64 [[X]], 63
; CHECK-NEXT: [[WIDEN:%.*]] = zext i64 [[SIGN]] to i128
; CHECK-NEXT: [[HI:%.*]] = shl nuw i128 [[WIDEN]], 64
; CHECK-NEXT: [[RES:%.*]] = or disjoint i128 [[HI]], [[LO]]
; CHECK-NEXT: [[RES:%.*]] = sext i64 [[X]] to i128
; CHECK-NEXT: store i128 [[RES]], ptr [[OUT]], align 16
; CHECK-NEXT: ret void
;
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