Why we optimize by time by default for < -O2 case?

LI Xin delphij at delphij.net
Mon Oct 8 19:53:58 PDT 2007

Bruce Evans wrote:
> 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.

Does this affect all platforms or is it i386 only, on the latest GCC

Xin LI <delphij at delphij.net>	http://www.delphij.net/
FreeBSD - The Power to Serve!

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