diff options
| author | David Majnemer <david.majnemer@gmail.com> | 2014-10-11 10:20:04 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-10-11 10:20:04 +0000 |
| commit | 171825a8cec198cad76ed9c032f537fd42e78325 (patch) | |
| tree | 79358a3e07def1c68eeac27324866e292f3d7dfd /lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | |
| parent | 9043f74acb70f48b6bb7717cf0e1b39ac259ac1b (diff) | |
InstCombine: Don't fold (X <<s log(INT_MIN)) /s INT_MIN to X
Consider the case where X is 2. (2 <<s 31)/s-2147483648 is zero but we
would fold to X. Note that this is valid when we are in the unsigned
domain because we require NUW: 2 <<u 31 results in poison.
This fixes PR21245.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219568 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineMulDivRem.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 8d004f2a0a2..b09198afff2 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -762,7 +762,8 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) { } } - if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1)))) || + if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1))) && + *C1 != C1->getBitWidth() - 1) || (!IsSigned && match(LHS, m_NUWShl(m_Value(X), m_APInt(C1))))) { APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned); APInt C1Shifted = APInt::getOneBitSet( |