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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 | 83d2e066c12d2ff42f07c90a4cf5495d2669a28a (patch) | |
| tree | 767beeb134d66b29d14cdc19afa583a375b30fca /llvm/lib/Target/README.txt | |
| parent | 161b7b66acf5664f25dfedac867286a62219fd9f (diff) | |
| download | bcm5719-llvm-83d2e066c12d2ff42f07c90a4cf5495d2669a28a.tar.gz bcm5719-llvm-83d2e066c12d2ff42f07c90a4cf5495d2669a28a.zip | |
Add a README entry noticed while investigating PR3216.
llvm-svn: 62558
Diffstat (limited to 'llvm/lib/Target/README.txt')
| -rw-r--r-- | llvm/lib/Target/README.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/llvm/lib/Target/README.txt b/llvm/lib/Target/README.txt index 4e4668698ad..756f38a6491 100644 --- a/llvm/lib/Target/README.txt +++ b/llvm/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 + +//===---------------------------------------------------------------------===// |
