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Re: Bugs in SSA-CCP and SSA-PRE optimizers
- From: Daniel Berlin <dberlin at dberlin dot org>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>, gcc at gcc dot gnu dot org
- Date: Tue, 17 Sep 2002 16:30:48 -0400
- Subject: Re: Bugs in SSA-CCP and SSA-PRE optimizers
Stop.
already, you are screwed.
CCP doesn't update the SSA representation, thus, PRE won't have
correct data.
I said that backwards, since PRE is run before CCP, but PRE doesn't
update the representaiton right now either.
If you run CCP alone, you'll get:
main()
{
int bla;
int foo;
int bar;
int T.1;
bla = 1;
foo = 2;
T.1 = 2;
bar = 3;
goto waffle;
return bar;
waffle:
bla = 1;
return 3;
}
Which PRE won't eliminate any of anyway.
CCP should be run before PRE, and after it.