Re: gcc4 optimization problems on intel mac
Re: gcc4 optimization problems on intel mac
- Subject: Re: gcc4 optimization problems on intel mac
- From: Richard Schreyer <email@hidden>
- Date: Tue, 23 Jan 2007 13:44:39 -0800
On Jan 23, 2007, at 1:34 PM, Paul Walmsley wrote:
Both of these problems only existed in our release builds, and
after some tweaking and testing, I determined that the problem was
related specifically to the optimization settings in GCC4. Under
*any* setting except -O0, these strange behaviors would reappear,
though without optimization everything runs normally.
I wouldn't necessarily assume that the bug is in compiler's
optimisation (though of course it can never be ruled out). I've
come across many 'release build only' bugs in the past that have
emerged as a result of the various differences between debug and
release builds. A few of the things to try would be:
To add to this, during our Intel bringup, I definitely did find
several of 'intel/optimized only' bugs, and the root cause was almost
always a latent issue in the code, and not the compiler.
Your best friend here is to set per-file optimization flags to narrow
the issue down to a single source file that is sensitive to the
optimization flags. Once you've gotten that far, you can use
#pragma optimization_level [0123]
to continue your binary search within the offending file(s).
Richard Schreyer
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