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[PowerPC] Remove README.txt entry

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This entry has been rendered irrelevant now that we have proper CR bit
tracking.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225211 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2015-01-05 21:41:26 +00:00
parent e4f1dcdb83
commit 92a87c67ee
1 changed files with 0 additions and 34 deletions
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34
lib/Target/PowerPC/README.txt
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@ -184,40 +184,6 @@ just fastcc.
===-------------------------------------------------------------------------=== ===-------------------------------------------------------------------------===
Compile this:
int foo(int a) {
int b = (a < 8);
if (b) {
return b * 3; // ignore the fact that this is always 3.
} else {
return 2;
}
}
into something not this:
_foo:
1) cmpwi cr7, r3, 8
mfcr r2, 1
rlwinm r2, r2, 29, 31, 31
1) cmpwi cr0, r3, 7
bgt cr0, LBB1_2 ; UnifiedReturnBlock
LBB1_1: ; then
rlwinm r2, r2, 0, 31, 31
mulli r3, r2, 3
blr
LBB1_2: ; UnifiedReturnBlock
li r3, 2
blr
In particular, the two compares (marked 1) could be shared by reversing one.
This could be done in the dag combiner, by swapping a BR_CC when a SETCC of the
same operands (but backwards) exists. In this case, this wouldn't save us
anything though, because the compares still wouldn't be shared.
===-------------------------------------------------------------------------===
Fold add and sub with constant into non-extern, non-weak addresses so this: Fold add and sub with constant into non-extern, non-weak addresses so this:
static int a; static int a;