On Wed, Dec 07, 2016 at 02:18:15PM -0700, Jeff Law wrote:
> On 12/05/2016 02:14 PM, Jakub Jelinek wrote:
> >Hi!
> >
> >As shown on the testcase, with K&R definitions and fn prototypes with
> >promoted types, we can end up computing caller's value ranges in wider
> >type than the parameter actually has in the function.
> >The problem with that is that wide_int_storage::from can actually wrap
> >around, so either as in the testcase we end up with invalid range (minimum
> >larger than maximum), or just with a range that doesn't cover all the values
> >the parameter can have.
> >The patch punts if the range bounds cast to type aren't equal to the
> >original values. Similarly (just theoretical), for pointers it only
> >optimizes if the caller's precision as at most as wide as the pointer,
> >if it would be wider, even ~[0, 0] range could actually be a NULL pointer
> >(some multiple of ~(uintptr_t)0 + (uintmax_t) 1).
> >
> >Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> >
> >2016-12-05 Jakub Jelinek <ja...@redhat.com>
> >
> > PR tree-optimization/78681
> > * ipa-prop.c (ipcp_update_vr): Punt if vr[i].min precision is bigger
> > then type's precision and vr[i].min or vr[i].max in type would wrap.
> >
> > * gcc.c-torture/compile/pr78681.c: New test.
> OK. If the work on the thread for 78365 produces fruit we can always go
> back and make this less pessimistic.
Richard actually prefers the other patch (still pending review).
Jakub
