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add a readme.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114303 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-09-19 00:34:58 +00:00
parent 222920d667
commit 702917d4e8
1 changed files with 25 additions and 0 deletions
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25
lib/Target/PowerPC/README.txt
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@ -37,6 +37,31 @@ _f3:
ori r3, r2, 65535
blr
===-------------------------------------------------------------------------===
This code:
unsigned add32carry(unsigned sum, unsigned x) {
unsigned z = sum + x;
if (sum + x < x)
z++;
return z;
}
Should compile to something like:
addc r3,r3,r4
addze r3,r3
instead we get:
add r3, r4, r3
cmplw cr7, r3, r4
mfcr r4 ; 1
rlwinm r4, r4, 29, 31, 31
add r3, r3, r4
Ick.
===-------------------------------------------------------------------------===