Re: Remove noce_mem_write_may_trap_or_fault_p in ifcvt

[Michael Matz <matz@suse.de>]

Hi,

On Wed, 25 Nov 2015, Jakub Jelinek wrote:

> > That looks bogus to me.  It misses asm()s and at least today 
> > nonfreeing_call_p too much checks what it sounds like it checks. In 
> > practice it might work though.  At least all the __sync_* and 
> > __atomic_* calls are _not_ barriers this way.  A pthread_mutex_lock is 
> > though as we don't have a builtin for it.
> > 
> > I'd change the above to a conservative
> > 
> >    if ((is_gimple_call (stmt) || is_gimple_asm (stmt)) && gimple_vuse (stmt))
> 
> nonfreeing_call_p is one necessary condition (if that is true, it means
> the call could mean that the first access does not trap while the second one
> does).

Yes, Richis test is conservatively catching this as well (it's clear the 
table for all calls and asms that even remotely can change memory state 
(well, when using gimple_vdef, not gimple_vuse).


Ciao,
Michael.