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| author | Dan Gohman <gohman@apple.com> | 2009-01-20 01:07:33 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2009-01-20 01:07:33 +0000 |
| commit | a340102f2e0086033f0ef5456a278f81d8937166 (patch) | |
| tree | ac3737e3127716167f28918d2830830acb498d45 /lib | |
| parent | 50187c2d138fe3f002e0a8c8f6c7c92939684ff5 (diff) | |
| download | external_llvm-a340102f2e0086033f0ef5456a278f81d8937166.zip external_llvm-a340102f2e0086033f0ef5456a278f81d8937166.tar.gz external_llvm-a340102f2e0086033f0ef5456a278f81d8937166.tar.bz2 | |
Add a README entry noticed while investigating PR3216.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62558 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/README.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 4e46686..756f38a 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1651,3 +1651,25 @@ globalopt to remove the "stored only" global. //===---------------------------------------------------------------------===// +This code: + +define inreg i32 @foo(i8* inreg %p) nounwind { + %tmp0 = load i8* %p + %tmp1 = ashr i8 %tmp0, 5 + %tmp2 = sext i8 %tmp1 to i32 + ret i32 %tmp2 +} + +could be dagcombine'd to a sign-extending load with a shift. +For example, on x86 this currently gets this: + + movb (%eax), %al + sarb $5, %al + movsbl %al, %eax + +while it could get this: + + movsbl (%eax), %eax + sarl $5, %eax + +//===---------------------------------------------------------------------===// |