Re: [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Jul 27, 2023 at 01:07:58PM +0000, Richard Biener wrote:
> On Thu, 27 Jul 2023, Jakub Jelinek wrote:
> 
> > On Thu, Jul 27, 2023 at 12:00:56PM +0000, Richard Biener wrote:
> > > The following fixes the lack of simplification of a vector shift
> > > by an out-of-bounds shift value.  For scalars this is done both
> > > by CCP and VRP but vectors are not handled there.  This results
> > > in PR91838 differences in outcome dependent on whether a vector
> > > shift ISA is available and thus vector lowering does or does not
> > > expose scalar shifts here.
> > > 
> > > The following adds a match.pd pattern to catch uniform out-of-bound
> > > shifts, simplifying them to zero when not sanitizing shift amounts.
> > > 
> > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > > 
> > > OK?
> > > 
> > > Thanks,
> > > Richard.
> > > 
> > > 	PR tree-optimization/91838
> > > 	* match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern.
> > 
> > The !(flag_sanitize & SANITIZE_SHIFT_EXPONENT)
> > should be !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT)
> > or maybe even
> > GIMPLE || !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT)
> > because the shift ubsan instrumentation is done on GENERIC, so it can be
> > optimized on GIMPLE even with ubsan.
> > 
> > Otherwise LGTM.
> 
> So like the following, will push after re-testing succeeded.

Yes, thanks.

	Jakub