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[InstCombine] Use m_NotForbidPoison when folding (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y) #114345

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Merged
merged 2 commits into from
Nov 1, 2024
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[InstCombine] Use m_NotForbidPoison when folding (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y) #114345

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a9958c4
[InstCombine] Add pre-commit tests. NFC.
dtcxzyw Oct 31, 2024
dee9d85
[InstCombine] Use `m_NotForbidPoison` when folding `(X u< Y) ? -1 : (…
dtcxzyw Oct 31, 2024
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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Expand Up @@ -1051,7 +1051,7 @@ static Value *canonicalizeSaturatedAdd(ICmpInst *Cmp, Value *TVal, Value *FVal,
// Strictness of the comparison is irrelevant.
X = Cmp0;
Y = Cmp1;
if (match(FVal, m_c_Add(m_Not(m_Specific(X)), m_Specific(Y)))) {
if (match(FVal, m_c_Add(m_NotForbidPoison(m_Specific(X)), m_Specific(Y)))) {
// (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y)
// (X u< Y) ? -1 : (Y + ~X) --> uadd.sat(Y, ~X)
BinaryOperator *BO = cast<BinaryOperator>(FVal);
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15 changes: 15 additions & 0 deletions llvm/test/Transforms/InstCombine/saturating-add-sub.ll
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Expand Up @@ -1890,6 +1890,21 @@ define <2 x i32> @uadd_sat_not_ugt_commute_add(<2 x i32> %x, <2 x i32> %yp) {
ret <2 x i32> %r
}

define <2 x i32> @uadd_sat_not_ugt_commute_add_partial_poison(<2 x i32> %x, <2 x i32> %yp) {
; CHECK-LABEL: @uadd_sat_not_ugt_commute_add_partial_poison(
; CHECK-NEXT: [[NOTX:%.*]] = xor <2 x i32> [[X:%.*]], <i32 -1, i32 poison>
; CHECK-NEXT: [[A:%.*]] = add nuw <2 x i32> [[YP:%.*]], [[NOTX]]
; CHECK-NEXT: [[C:%.*]] = icmp ugt <2 x i32> [[YP]], [[X]]
; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[C]], <2 x i32> <i32 -1, i32 -1>, <2 x i32> [[A]]
; CHECK-NEXT: ret <2 x i32> [[R]]
;
%notx = xor <2 x i32> %x, <i32 -1, i32 poison>
%a = add nuw <2 x i32> %yp, %notx
%c = icmp ugt <2 x i32> %yp, %x
%r = select <2 x i1> %c, <2 x i32> <i32 -1, i32 -1>, <2 x i32> %a
ret <2 x i32> %r
}

define i32 @uadd_sat_not_commute_select(i32 %x, i32 %y) {
; CHECK-LABEL: @uadd_sat_not_commute_select(
; CHECK-NEXT: [[NOTX:%.*]] = xor i32 [[X:%.*]], -1
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