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Re: inconsistent gcc performance on this code
- From: Daniel Jacobowitz <drow at false dot org>
- To: Jason Papadopoulos <jasonp at boo dot net>
- Cc: gcc at gcc dot gnu dot org
- Date: Sun, 18 Jul 2004 12:55:59 -0400
- Subject: Re: inconsistent gcc performance on this code
- References: <email@example.com>
On Sun, Jul 18, 2004 at 12:02:43PM -0400, Jason Papadopoulos wrote:
> Compiling fgt5b with '-O3 -fomit-frame-pointer' generates
> code that runs ~20% faster and is ~25% smaller than fgt5a.
> The only difference between the two files is that 5a
> writes each result to a different variable, while 5b
> sometimes reuses the same set of 8 variables for common
> (temporary) operations.
You may want to compare the output of GCC HEAD (pre-3.5) on both files.
SSA form excels at this sort of splitting.