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| author | David Majnemer <david.majnemer@gmail.com> | 2014-11-22 20:00:41 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-11-22 20:00:41 +0000 |
| commit | 369d8fa34f9df5c157fce855e9f89b83ef0d2e30 (patch) | |
| tree | 98db080113683fd2f6d81026ecbbd661d4a04596 | |
| parent | 89bcfdb9563494fe8bcd1a415bc8108f682dd0a9 (diff) | |
InstCombine: Propagate exact for (sdiv X, Pow2) -> (udiv X, Pow2)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222625 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 6 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/div.ll | 11 |
2 files changed, 15 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 216177ff2b4..d7847ca5ccd 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -1102,12 +1102,14 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { return BO; } - if (match(Op1, m_Shl(m_Power2(), m_Value()))) { + if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/true, 0, AT, &I, DT)) { // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y) // Safe because the only negative value (1 << Y) can take on is // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have // the sign bit set. - return BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); + auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); + BO->setIsExact(I.isExact()); + return BO; } } } diff --git a/test/Transforms/InstCombine/div.ll b/test/Transforms/InstCombine/div.ll index cfe346e1f2b..e0ff07baae7 100644 --- a/test/Transforms/InstCombine/div.ll +++ b/test/Transforms/InstCombine/div.ll @@ -314,3 +314,14 @@ define i32 @test35(i32 %A) { ; CHECK-NEXT: %[[udiv:.*]] = udiv exact i32 %[[and]], 2147483647 ; CHECK-NEXT: ret i32 %[[udiv]] } + +define i32 @test36(i32 %A) { + %and = and i32 %A, 2147483647 + %shl = shl nsw i32 1, %A + %mul = sdiv exact i32 %and, %shl + ret i32 %mul +; CHECK-LABEL: @test36( +; CHECK-NEXT: %[[and:.*]] = and i32 %A, 2147483647 +; CHECK-NEXT: %[[shr:.*]] = lshr exact i32 %[[and]], %A +; CHECK-NEXT: ret i32 %[[shr]] +} |