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Re: Revision 144098 (d.d. Wed Feb 11 08:56:41 2009 UTC (4 weeks ago)) is not a regression bug fix.
- From: Paolo Bonzini <bonzini at gnu dot org>
- To: Toon Moene <toon at moene dot org>
- Cc: gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Thu, 12 Mar 2009 08:38:25 +0100
- Subject: Re: Revision 144098 (d.d. Wed Feb 11 08:56:41 2009 UTC (4 weeks ago)) is not a regression bug fix.
- References: <49B832FA.email@example.com>
1) As multiple people said, it *was* a regression bug fix. It actually
fixed two regressions. (That it fixed the second was discovered only
after I committed it). I'm sorry that it caused problems for you (even
though it's actually lucky for GCC), but I can't help saying that it
might have been the other way and it might have improved your weather
forecasting app by 10-20% or more, as it did on one or two SPEC benchmarks.
2) I apologize for the bad quality of the patch. But I tested it on
bootstrap, SPEC2000, and of course the testcase, and it had no problems.
This testing takes more than 24 hours on my machine and it is more than
is requested usually--and I did for correctness, not for performance
In addition, all but one of the fixes that H.J. made (and for which I
have to thank him) were unrecognizable insns due to a misunderstanding
of how peephole2 worked; I thought it recognized the produced
instructions, instead apparently it's the only optimization in GCC where
this does not happen. I have a patch to fix this in GCC 4.5.
3) I look forward to seeing the result of the tests H.J. asked you to
do, so that at least we can find which peephole2 is responsible. If you
want to revert it now, go ahead. I don't see any problems with that and
I can approve the reversal of my patch. I'll try again for 4.5 and
propose the patch for 4.5.1.
Alternatively, let's use these 48 hours constructively to finish the
above test, look at the code and try and understand the cause of the
failure. I'll do my part by looking at the code *now*.
4) I would have appreciated being CCed on the message.
> I run a weather forecasting system 4 times daily to test it out.
We can only thank you for this. Please keep the same attitude towards
the people that try to improve the compiler.