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| author | David Majnemer <david.majnemer@gmail.com> | 2014-08-16 09:23:42 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-08-16 09:23:42 +0000 |
| commit | 1a0bbc8a5c1e9cb9888ee8c2ba5f46752636e47f (patch) | |
| tree | 6657cb7ee84f74e63d14cb614e002192e320f0cc /llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | |
| parent | 2873594709b9c10914330312cf3f7ea5ff222b93 (diff) | |
| download | bcm5719-llvm-1a0bbc8a5c1e9cb9888ee8c2ba5f46752636e47f.tar.gz bcm5719-llvm-1a0bbc8a5c1e9cb9888ee8c2ba5f46752636e47f.zip | |
InstCombine: Fix a potential bug in 0 - (X sdiv C) -> (X sdiv -C)
While *most* (X sdiv 1) operations will get caught by InstSimplify, it
is still possible for a sdiv to appear in the worklist which hasn't been
simplified yet.
This means that it is possible for 0 - (X sdiv 1) to get transformed
into (X sdiv -1); dividing by -1 can make the transform produce undef
values instead of the proper result.
Sorry for the lack of testcase, it's a bit problematic because it relies
on the exact order of operations in the worklist.
llvm-svn: 215818
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index b18c10dd57b..22cc34d861a 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1583,7 +1583,7 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { // 0 - (X sdiv C) -> (X sdiv -C) provided the negation doesn't overflow. if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero()) && - !C->isMinSignedValue()) + !C->isMinSignedValue() && !C->isOneValue()) return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); // 0 - (X << Y) -> (-X << Y) when X is freely negatable. |
