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A relatively simple PPC optimization.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33709 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-01-31 19:49:20 +00:00
parent 6ffbe17b3c
commit 95b9d6e5d8
1 changed files with 27 additions and 0 deletions
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27
lib/Target/PowerPC/README.txt
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@ -595,3 +595,30 @@ register of that class. If it is then later necessary to spill that reg, so be
it.
===-------------------------------------------------------------------------===
We compile this:
int test(_Bool X) {
return X ? 524288 : 0;
}
to:
_test:
cmplwi cr0, r3, 0
lis r2, 8
li r3, 0
beq cr0, LBB1_2 ;entry
LBB1_1: ;entry
mr r3, r2
LBB1_2: ;entry
blr
instead of:
_test:
addic r2,r3,-1
subfe r0,r2,r3
slwi r3,r0,19
blr
This sort of thing occurs a lot due to globalopt.
===-------------------------------------------------------------------------===