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| author | Chris Lattner <sabre@nondot.org> | 2009-01-09 07:47:06 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2009-01-09 07:47:06 +0000 |
| commit | a80d668215be2b9a0f564d85d0506e6a3dbe7ba2 (patch) | |
| tree | facc394ce930ad7eb43485039e483c7b437beaa2 /test/Transforms/InstCombine/icmp.ll | |
| parent | 6d6b4106985378a5b8714dc74b9d7a077eb2471b (diff) | |
| download | llvm-a80d668215be2b9a0f564d85d0506e6a3dbe7ba2.tar.gz llvm-a80d668215be2b9a0f564d85d0506e6a3dbe7ba2.tar.bz2 llvm-a80d668215be2b9a0f564d85d0506e6a3dbe7ba2.tar.xz | |
Implement rdar://6480391, extending of equality icmp's to avoid a truncation.
I noticed this in the code compiled for a routine using std::map, which produced
this code:
%25 = tail call i32 @memcmp(i8* %24, i8* %23, i32 6) nounwind readonly
%.lobit.i = lshr i32 %25, 31 ; <i32> [#uses=1]
%tmp.i = trunc i32 %.lobit.i to i8 ; <i8> [#uses=1]
%toBool = icmp eq i8 %tmp.i, 0 ; <i1> [#uses=1]
br i1 %toBool, label %bb3, label %bb4
which compiled to:
call L_memcmp$stub
shrl $31, %eax
testb %al, %al
jne LBB1_11 ##
with this change, we compile it to:
call L_memcmp$stub
testl %eax, %eax
js LBB1_11
This triggers all the time in common code, with patters like this:
%169 = and i32 %ply, 1 ; <i32> [#uses=1]
%170 = trunc i32 %169 to i8 ; <i8> [#uses=1]
%toBool = icmp ne i8 %170, 0 ; <i1> [#uses=1]
%7 = lshr i32 %6, 24 ; <i32> [#uses=1]
%9 = trunc i32 %7 to i8 ; <i8> [#uses=1]
%10 = icmp ne i8 %9, 0 ; <i1> [#uses=1]
etc
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61985 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/Transforms/InstCombine/icmp.ll')
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index bb69ba3be4..27136d6943 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -1,5 +1,4 @@ ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep icmp -; END. define i32 @test1(i32 %X) { entry: |