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[InstCombine] Return nsw when convert shl to mul if its on the RHS #121671

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[InstCombine] Return nsw when convert shl to mul if its on the RHS #121671

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6 changes: 3 additions & 3 deletions llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2099,9 +2099,9 @@ static Instruction *simplifyIRemMulShl(BinaryOperator &I,
return false;
};

bool Op0PreserveNSW = true, Op1PreserveNSW = true;
bool Op0PreserveNSW = true, Unused;
if (MatchShiftOrMulXC(Op0, X, Y, Op0PreserveNSW) &&
MatchShiftOrMulXC(Op1, X, Z, Op1PreserveNSW)) {
MatchShiftOrMulXC(Op1, X, Z, Unused)) {
// pass
} else if (MatchShiftCX(Op0, Y, X) && MatchShiftCX(Op1, Z, X)) {
ShiftByX = true;
Expand Down Expand Up @@ -2137,7 +2137,7 @@ static Instruction *simplifyIRemMulShl(BinaryOperator &I,
};

OverflowingBinaryOperator *BO1 = cast<OverflowingBinaryOperator>(Op1);
bool BO1HasNSW = Op1PreserveNSW && BO1->hasNoSignedWrap();
bool BO1HasNSW = BO1->hasNoSignedWrap();
bool BO1HasNUW = BO1->hasNoUnsignedWrap();
bool BO1NoWrap = IsSRem ? BO1HasNSW : BO1HasNUW;
// (rem (mul X, Y), (mul nuw/nsw X, Z))
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4 changes: 1 addition & 3 deletions llvm/test/Transforms/InstCombine/rem-mul-shl.ll
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Expand Up @@ -388,9 +388,7 @@ define i8 @srem_XY_XZ_with_CY_gt_CZ_drop_nsw(i8 noundef %X) {
define i8 @srem_XY_XZ_with_CY_gt_CZ_drop_nsw_commuted(i8 noundef %X) {
; CHECK-LABEL: @srem_XY_XZ_with_CY_gt_CZ_drop_nsw_commuted(
; CHECK-NEXT: [[BO0:%.*]] = mul nsw i8 [[X:%.*]], 127
; CHECK-NEXT: [[BO1:%.*]] = shl nsw i8 [[X]], 7
; CHECK-NEXT: [[R:%.*]] = srem i8 [[BO0]], [[BO1]]
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: ret i8 [[BO0]]
;
%BO0 = mul nsw i8 %X, 127
%BO1 = shl nsw i8 %X, 7
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