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[Bug target/27827] gcc 4 produces worse x87 code on all platforms than gcc 3
- From: "whaley at cs dot utsa dot edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 31 May 2006 01:09:43 -0000
- Subject: [Bug target/27827] gcc 4 produces worse x87 code on all platforms than gcc 3
- References: <bug-27827-12761@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from whaley at cs dot utsa dot edu 2006-05-31 01:09 -------
Subject: Re: gcc 4 produces worse x87 code on all platforms than gcc 3
Yes, I agree it is an x86/x86_64 issue. I have not yet scoped the performance
of any of the other architectures with gcc 4 vs. 3: since 90% of my users use
an x86 of some sort, I can't switch to gcc 4 support until the x86 performance
is reasonable. It seems the x87 performance always goes down with any big gcc
change (bugzilla 4991 is a similar performance drop between 2.x and 3.0, though
the issues are not the exact same), probably because its oddball 2-op assembler
/ x87 stack doesn't map well to the more sane ISAs, which all compiler guys
strongly prefer :)
Thanks,
Clint
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27827