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Re: [PATCH] Fix PR52881, more loop preserving fallout with RTL optimizers
- From: Steven Bosscher <stevenb dot gcc at gmail dot com>
- To: Richard Guenther <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Tue, 10 Apr 2012 17:46:19 +0200
- Subject: Re: [PATCH] Fix PR52881, more loop preserving fallout with RTL optimizers
- References: <Pine.LNX.firstname.lastname@example.org>
On Tue, Apr 10, 2012 at 4:56 PM, Richard Guenther <email@example.com> wrote:
> I'm sure more RTL optimiziation fallout will pop up - and I wonder
> if we should simply avoid modifying the CFG all over the place and
> instead do that in cleanup_cfg. ?Thus, in the if-conversion case,
> simply do the speculation and leave the empty forwarder blocks
> to be cleaned up by cleanup_cfg (or for CSE to leave unconditional
> jumps conditional, as if (0/1), for example).
The problem with that could be that if(0|1) is not a valid instruction
for every machine. You may need to set a register (pseudo, or hard
reg) that may not be available (e.g. if it is live).