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author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-22 18:47:44 +0000 |
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committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-22 18:47:44 +0000 |
commit | e7cf062537e898f830565db5dbf99ae9c928399e (patch) | |
tree | 3c87d0506e38a3039f8e6df7fc0ed061d232dd8c /test/CodeGen/X86/shrink-compare.ll | |
parent | eac0c9dc7759b013bbe831ace1afa37bc46915c6 (diff) | |
download | llvm-e7cf062537e898f830565db5dbf99ae9c928399e.tar.gz llvm-e7cf062537e898f830565db5dbf99ae9c928399e.tar.bz2 llvm-e7cf062537e898f830565db5dbf99ae9c928399e.tar.xz |
DAGCombine: fold "(zext x) == C" into "x == (trunc C)" if the trunc is lossless.
On x86 this allows to fold a load into the cmp, greatly reducing register pressure.
movzbl (%rdi), %eax
cmpl $47, %eax
->
cmpb $47, (%rdi)
This shaves 8k off gcc.o on i386. I'll leave applying the patch in README.txt to Chris :)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130005 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/CodeGen/X86/shrink-compare.ll')
-rw-r--r-- | test/CodeGen/X86/shrink-compare.ll | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/test/CodeGen/X86/shrink-compare.ll b/test/CodeGen/X86/shrink-compare.ll new file mode 100644 index 0000000000..7eaf9411c1 --- /dev/null +++ b/test/CodeGen/X86/shrink-compare.ll @@ -0,0 +1,36 @@ +; RUN: llc < %s -march=x86-64 | FileCheck %s + +declare void @bar() + +define void @test1(i32* nocapture %X) nounwind { +entry: + %tmp1 = load i32* %X, align 4 + %and = and i32 %tmp1, 255 + %cmp = icmp eq i32 %and, 47 + br i1 %cmp, label %if.then, label %if.end + +if.then: + tail call void @bar() nounwind + br label %if.end + +if.end: + ret void +; CHECK: test1: +; CHECK: cmpb $47, (%rdi) +} + +define void @test2(i32 %X) nounwind { +entry: + %and = and i32 %X, 255 + %cmp = icmp eq i32 %and, 47 + br i1 %cmp, label %if.then, label %if.end + +if.then: + tail call void @bar() nounwind + br label %if.end + +if.end: + ret void +; CHECK: test2: +; CHECK: cmpb $47, %dil +} |