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[Bug middle-end/40029] [4.5 Regression] Big degradation on swim/mgrid on powerpc 32/64 after alias improvement merge (gcc r145494)
- From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 27 May 2009 20:57:52 -0000
- Subject: [Bug middle-end/40029] [4.5 Regression] Big degradation on swim/mgrid on powerpc 32/64 after alias improvement merge (gcc r145494)
- References: <bug-40029-16550@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from rguenth at gcc dot gnu dot org 2009-05-27 20:57 -------
Actually PRE seems to be more powerful than predictive commoning here. We
just lose one opportunity while gaining. With predictive commoning we have
8 loads and 4 stores, 11 multiplications and one division.
With PRE it is 6 loads and 4 stores, 10 multiplications and one division.
The only thing we gain from predictive commoning in 4.4 is unrolling the
loop once.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40029