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Re: Some statement counts for gcc
- From: Zack Weinberg <zack at codesourcery dot com>
- To: Brad Lucier <lucier at math dot purdue dot edu>
- Cc: gcc at gcc dot gnu dot org, Jan Hubicka <jh at suse dot cz>
- Date: Mon, 26 Aug 2002 00:16:57 -0700
- Subject: Re: Some statement counts for gcc
- References: <200208252304.g7PN4Bc18560@banach.math.purdue.edu>
On Sun, Aug 25, 2002 at 06:04:11PM -0500, Brad Lucier wrote:
> branch prediction : 165.11 (33%) usr 0.07 ( 1%) sys 165.50 (33%) wall
> A surprising (to me) number of lines in real.c are executed; I might look
> there to see what's going on.
The branch predictor uses emulated floating point numbers internally.
Jan Hubicka has explained why this is currently necessary -- can't
find the message at the moment though. However, real.c is indeed
quite slow; I suspect that accounts entirely for the amount of time
spent in this patch
If I remember correctly this code has a very complicated flow graph,
and branch prediction may not help much; perhaps the right thing is
to detect code like this and disable that optimization.