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Add a README entry noticed while investigating PR3216.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62558 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-01-20 01:07:33 +00:00
parent f5add58549
commit 8289b05c4c
1 changed files with 22 additions and 0 deletions
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22
lib/Target/README.txt
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@ -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
//===---------------------------------------------------------------------===//