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Re: maybe_infinite_loop?

From: "Andrew Pinski" <pinskia at gmail dot com>
To: "Mike Stump" <mrs at apple dot com>
Cc: "GCC Development" <gcc at gcc dot gnu dot org>, "Zdenek Dvorak" <rakdver at atrey dot karlin dot mff dot cuni dot cz>
Date: Sat, 21 Apr 2007 16:20:38 -0700
Subject: Re: maybe_infinite_loop?
References: <1F93B8AD-417C-4DE8-8D7E-03CC6A42DEF2@apple.com>

On 4/21/07, Mike Stump <mrs@apple.com> wrote:

We still have some lno bits in our tree.  We tried to remove them and
found:
Of all the LNO bits, the last major bits seems to be the below bit.
I don't even know if it is responsible for the benefit we see.  I
thought I'd mention it, as a 2-3% win on two of the spec tests seems
worthwhile.


The only benifit as far as I can tell is causing an extra call at the
tree level which could cause aliasing analysis to go wrong with call
clobbered variables.  The remove empty loop pass in 4.1.0 and above
removes more empty loops than the LNO patch could ever remove.  So
really I think you are just seeing bogus effects of slightly different
aliasing and register pressure.  Nothing to get your hopes up at
anyways.

Thanks,
Andrew Pinski

References:
- maybe_infinite_loop?
  - From: Mike Stump

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