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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2012-10-13 10:39:49 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2012-10-13 10:39:49 +0000 |
| commit | 444dccecfc6c6d0dad4f400141a12f9ca76943d8 (patch) | |
| tree | cf6c680b2f5dcd504d8c2e431788672778843a34 /test/CodeGen/X86/select.ll | |
| parent | c2fcf1a67126a079e34f04bd09a50ae85fdd9469 (diff) | |
| download | llvm-444dccecfc6c6d0dad4f400141a12f9ca76943d8.tar.gz llvm-444dccecfc6c6d0dad4f400141a12f9ca76943d8.tar.bz2 llvm-444dccecfc6c6d0dad4f400141a12f9ca76943d8.tar.xz | |
X86: Promote i8 cmov when both operands are coming from truncates of the same width.
X86 doesn't have i8 cmovs so isel would emit a branch. Emitting branches at this
level is often not a good idea because it's too late for many optimizations to
kick in. This solution doesn't add any extensions (truncs are free) and tries
to avoid introducing partial register stalls by filtering direct copyfromregs.
I'm seeing a ~10% speedup on reading a random .png file with libpng15 via
graphicsmagick on x86_64/westmere, but YMMV depending on the microarchitecture.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165868 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/CodeGen/X86/select.ll')
| -rw-r--r-- | test/CodeGen/X86/select.ll | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/test/CodeGen/X86/select.ll b/test/CodeGen/X86/select.ll index 2e39473057..f4c8d9e767 100644 --- a/test/CodeGen/X86/select.ll +++ b/test/CodeGen/X86/select.ll @@ -344,3 +344,16 @@ entry: ; ATOM: negw ; ATOM: sbbw } + +define i8 @test18(i32 %x, i8 zeroext %a, i8 zeroext %b) nounwind { + %cmp = icmp slt i32 %x, 15 + %sel = select i1 %cmp, i8 %a, i8 %b + ret i8 %sel +; CHECK: test18: +; CHECK: cmpl $15 +; CHECK: cmovll + +; ATOM: test18: +; ATOM: cmpl $15 +; ATOM: cmovll +} |