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| 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 | fe7fccff11dd78a126199a35b428537385d316a2 (patch) | |
| tree | b2d6bf98c4aa5b24d0f32caad91a7f777ea5b2ac /llvm/lib/Transforms | |
| parent | cb9d59665531cb2a894ac8af7e7cf476fba40600 (diff) | |
| download | bcm5719-llvm-fe7fccff11dd78a126199a35b428537385d316a2.tar.gz bcm5719-llvm-fe7fccff11dd78a126199a35b428537385d316a2.zip | |
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.
llvm-svn: 219568
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 8d004f2a0a2..b09198afff2 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/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( |
