Why we optimize by time by default for < -O2 case?
Bruce Evans
brde at optusnet.com.au
Mon Oct 8 19:34:14 PDT 2007
On Mon, 8 Oct 2007, LI Xin wrote:
> I wonder why we want to optimize by time by default and not by space by
> default for the system compiler, does the reasoning still hold true?
-O means optimize for time if possible.
> The commit log said:
>
> Modified files:
> contrib/gcc toplev.c
> Log:
> Clarify revision 1.14:
> Gcc 3.1's -O0 and -O1 actually optimized alignment for space, but we feel
> it should optimize alignment for time like Gcc 2.95 used to. Optimization
> for space should give 1-byte alignment on i386's, but doesn't quite.
>
> Revision Changes Path
> 1.15 +0 -0 src/contrib/gcc/toplev.c
Without this change, -O pessimizes for time.
Bruce
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