On Tue, 6 Dec 2016, Jakub Jelinek wrote:
> On Tue, Dec 06, 2016 at 09:36:55AM +0100, Richard Biener wrote:
> > > 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?
> >
> > Ok, but I wonder whether this also addresses PR78365 which has a
> > patch pending (to be reviewed by IPA maintainers) that makes propagation
> > across such calls more sensible by recording type information in
> > the jump functions.
>
> It is effectively a dup. So, my patch fixes the PR78365 testcase and I bet
> (though haven't tried, but it is extremely likely) that the other patch
> fixes PR78681 testcase.
> So, do you want me to add the pr78365.c testcase to my patch, or prefer
> the other patch? OT, in the other patch I've noticed incorrect formatting:
> + parm ?
> + TREE_TYPE (parm) :
> NULL_TREE);
I prefer the other patch (well, the other approach, didn't look into
the patch in detail).
Richard.
> > > 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.
> > >
> > > --- gcc/ipa-prop.c.jj 2016-11-25 18:11:05.000000000 +0100
> > > +++ gcc/ipa-prop.c 2016-12-05 18:48:48.853882864 +0100
> > > @@ -5709,8 +5709,23 @@ ipcp_update_vr (struct cgraph_node *node
> > > {
> > > tree type = TREE_TYPE (ddef);
> > > unsigned prec = TYPE_PRECISION (type);
> > > + unsigned mprec = wi::get_precision (vr[i].min);
> > > + gcc_assert (mprec == wi::get_precision (vr[i].max));
> > > if (INTEGRAL_TYPE_P (TREE_TYPE (ddef)))
> > > {
> > > + if (prec < mprec)
> > > + {
> > > + /* If there is a disagreement between callers and callee
> > > + on the argument type, e.g. when using K&R function
> > > + definitions, punt if vr[i].min or vr[i].max are outside
> > > + of type's precision. */
> > > + wide_int m = wi::ext (vr[i].min, prec, TYPE_SIGN (type));
> > > + if (m != vr[i].min)
> > > + continue;
> > > + m = wi::ext (vr[i].max, prec, TYPE_SIGN (type));
> > > + if (m != vr[i].max)
> > > + continue;
> > > + }
> > > if (dump_file)
> > > {
> > > fprintf (dump_file, "Setting value range of param %u ", i);
> > > @@ -5729,6 +5744,7 @@ ipcp_update_vr (struct cgraph_node *node
> > > }
> > > else if (POINTER_TYPE_P (TREE_TYPE (ddef))
> > > && vr[i].type == VR_ANTI_RANGE
> > > + && mprec <= prec
> > > && wi::eq_p (vr[i].min, 0)
> > > && wi::eq_p (vr[i].max, 0))
> > > {
> > > --- gcc/testsuite/gcc.c-torture/compile/pr78681.c.jj 2016-12-05
> > > 19:51:15.353646309 +0100
> > > +++ gcc/testsuite/gcc.c-torture/compile/pr78681.c 2016-12-05
> > > 19:50:57.000000000 +0100
> > > @@ -0,0 +1,27 @@
> > > +/* PR tree-optimization/78681 */
> > > +
> > > +struct S { char b; };
> > > +char d, e, f, l, m;
> > > +struct S n;
> > > +int bar (char, char);
> > > +static void foo (struct S *, int, int, int, int);
> > > +
> > > +static void
> > > +foo (x, g, h, i, j)
> > > + struct S *x;
> > > + char g, h, i, j;
> > > +{
> > > + char k;
> > > + for (k = 0; k <= j; k++)
> > > + if (bar (g, k))
> > > + for (; i; k++)
> > > + if (d)
> > > + x->b = g;
> > > +}
> > > +
> > > +void
> > > +baz (int q)
> > > +{
> > > + foo (&n, m, l, f, 1);
> > > + foo (&n, m, e, f, e - 1);
> > > +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
