Re: [PATCH] tree-optimization/105080 - make sure SCEV is available for ranger

[Richard Biener <rguenther@suse.de>]

On Mon, 28 Mar 2022, Richard Biener wrote:

> On Mon, 28 Mar 2022, Jakub Jelinek wrote:
> 
> > On Mon, Mar 28, 2022 at 03:16:24PM +0200, Richard Biener wrote:
> > > When doing format diagnostics at -O0 we should make sure to make
> > > SCEV available to avoid false positives due to ranges we otherwise
> > > can trivially compute.
> > > 
> > > Bootstrap and regtest running on x86_64-unknown-linux-gnu.
> > > 
> > > OK if that succeeds?
> > 
> > Doesn't this slow down -O0 compilation too much?
> 
> Not if you do not enable the warning.  If you enable it you
> probably are set to pay for it.  Are you specifically
> concerned about the cases where SCEV / niter analysis take
> a lot of time or are you concerned about the constant overhead
> of enabling loops/SCEV?

One concern might be that loop_optimizer_init (LOOPS_NORMAL)
changes the IL but the early pass just emits diagnostics so
when disabled/enabled (based purely on diagnostic options)
generated code could change.  Note SCEV currently has (undocumented)
contraints on loops so just AVOID_CFG_MANIPULATIONS doens't work
there without putting it extra safety checks to give up.

Richard.

> Richard.
> 
> > > 2022-03-28  Richard Biener  <rguenther@suse.de>
> > > 
> > > 	PR tree-optimization/105080
> > > 	* tree-ssa-strlen.cc (printf_strlen_execute): Always init
> > > 	loops and SCEV.
> > > 
> > > 	* gcc.dg/pr105080.c: New testcase.
> > 
> > 	Jakub
> > 
> > 
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)