Subject: re: Changes to crunchgen
To: None <email@example.com>
From: matthew green <firstname.lastname@example.org>
Date: 10/04/2001 16:28:59
What I've observed is that, with egcs (old toolchain) on i386, you
-Os < -O < -O2
but you sometimes see:
-O < -Os < -O2
-Os turns off certain optimizations which tend to bloat code size and
increase instruction count; it turned out that, for i386, it reduced
instruction count but increased object code size for the one case I
looked at in detail.
The differences were often small, but with our install media commonly
very close to the limit, a few bytes can make a difference..
this is different to my tests on the sparc a while back. i think this
is with egcs 1.1.x or so. i found that
-Os < -O2 << -O1
-O2 < -Os << -O1
ie, that -Os and -O2 were very very similar, but -O1 was a LOT worse.
-O0 is worse again as to be expected.
this is all from memory so i could be mis-remembering.