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| author | David Majnemer <david.majnemer@gmail.com> | 2014-10-13 22:37:51 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-10-13 22:37:51 +0000 |
| commit | db0773089f8a1944fa3c73e5be78e88b258318ca (patch) | |
| tree | 7af69fa517a84411f253ca47d27b8377474d2df1 /llvm/test/Transforms/InstCombine/sub.ll | |
| parent | b75d8f300cbfba07aad4442a8ef600194e5a8a42 (diff) | |
| download | bcm5719-llvm-db0773089f8a1944fa3c73e5be78e88b258318ca.tar.gz bcm5719-llvm-db0773089f8a1944fa3c73e5be78e88b258318ca.zip | |
InstCombine: Fix miscompile in X % -Y -> X % Y transform
We assumed that negation operations of the form (0 - %Z) resulted in a
negative number. This isn't true if %Z was originally negative.
Substituting the negative number into the remainder operation may result
in undefined behavior because the dividend might be INT_MIN.
This fixes PR21256.
llvm-svn: 219639
Diffstat (limited to 'llvm/test/Transforms/InstCombine/sub.ll')
| -rw-r--r-- | llvm/test/Transforms/InstCombine/sub.ll | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/llvm/test/Transforms/InstCombine/sub.ll b/llvm/test/Transforms/InstCombine/sub.ll index e0b3a07c233..1d1bedc0a7b 100644 --- a/llvm/test/Transforms/InstCombine/sub.ll +++ b/llvm/test/Transforms/InstCombine/sub.ll @@ -142,8 +142,9 @@ define i32 @test15(i32 %A, i32 %B) { %D = srem i32 %B, %C ret i32 %D ; CHECK-LABEL: @test15( -; CHECK: %D = srem i32 %B, %A -; CHECK: ret i32 %D +; CHECK: %[[sub:.*]] = sub i32 0, %A +; CHECK-NEXT: %[[rem:.*]] = srem i32 %B, %[[sub]] +; CHECK: ret i32 %[[rem]] } define i32 @test16(i32 %A) { |
