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Re: RFC: Optimizing for 386



On Wed, 2005-01-19 at 18:24 +0100, Peter Backlund wrote:
> Has anyone been testing -Os (optimize for size) instead of -O2 on any
> greater scale? Fitting as much as possible in L1-cache is a great way to
> obtain high performance. 

-Os versus -O2 for OpenOffice.org (on RHEL3, with gcc 3.3.2) produced no
real benefit, besides a small reduction in library size (7-8 MB total
through the whole set of libraries).  It also made OOo hit optimization
bugs (either gcc bugs or OOo code bugs) that had stuff as simple as file
opening crashing.  Most likely, its OOo's aggressive use of inline
functions and complex templates that causes there to be only a minor
benefit.

For other programs though, -Os may well produce better-running, small-
therefore-better-for-cache binaries.

Dan


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