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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-12-24 17:31:38 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-12-24 17:31:38 +0000 |
| commit | 1fdfae05b0a4356d1ed0633bf3d6cdc6eba2e173 (patch) | |
| tree | ccea4fe8b620b42f8d495936698c5c6f46e543d7 /test/Transforms/InstCombine/sub-xor.ll | |
| parent | ce618af3e880ae0ec0ddd81aca8ed5bbd4096ae4 (diff) | |
| download | llvm-1fdfae05b0a4356d1ed0633bf3d6cdc6eba2e173.tar.gz llvm-1fdfae05b0a4356d1ed0633bf3d6cdc6eba2e173.tar.bz2 llvm-1fdfae05b0a4356d1ed0633bf3d6cdc6eba2e173.tar.xz | |
InstCombine: Canonicalize (2^n)-1 - x into (2^n)-1 ^ x iff x is known to be smaller than 2^n.
This has the obvious advantage of being commutable and is always a win on x86 because
const - x wastes a register there. On less weird architectures this may lead to
a regression because other arithmetic doesn't fuse with it anymore. I'll address that
problem in a followup.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147254 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/Transforms/InstCombine/sub-xor.ll')
| -rw-r--r-- | test/Transforms/InstCombine/sub-xor.ll | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/test/Transforms/InstCombine/sub-xor.ll b/test/Transforms/InstCombine/sub-xor.ll new file mode 100644 index 0000000000..41e01fbdae --- /dev/null +++ b/test/Transforms/InstCombine/sub-xor.ll @@ -0,0 +1,12 @@ +; RUN: opt -instcombine -S < %s | FileCheck %s + +define i32 @test1(i32 %x) nounwind { + %and = and i32 %x, 31 + %sub = sub i32 63, %and + ret i32 %sub + +; CHECK: @test1 +; CHECK-NEXT: and i32 %x, 31 +; CHECK-NEXT: xor i32 %and, 63 +; CHECK-NEXT: ret +} |