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Re: [PATCH] Don't create zero based pointer IVs in ivopts (PR tree-optimization/36038)
The patch looks good on spec2000 for ppc. I just have to verify some
small variations. Will report OK or not, soon.
Thanks,
Luis
On Tue, 2008-10-21 at 12:08 -0200, Luis Machado wrote:
> Jakub,
>
> Thanks for the patch. Give me a couple days and i will provide the spec
> results on PPC with the patch applied.
>
> Thanks,
> Luis
>
> On Tue, 2008-10-21 at 01:06 +0200, Jakub Jelinek wrote:
> > Hi!
> >
> > The testcase below fails because ivopts chooses a pointer type ivtmp
> > { 0B, +, -8 }_1 and then VRP optimizes that out, as it assumes that ivtmp
> > must be NULL. IMHO when adding IV alternative with initial value zero,
> > for pointers that IV should use sizetype, not pointer, as the IV is
> > necessarily just an offset that will be added to some base pointer.
> >
> > The following patch fixes the testcase on powerpc64-linux (the testcase
> > after ivopts is very similar, except the ivtmp is in sizetype and doesn't
> > need to be casted to an integer type and back to pointer all the time)
> > and passes bootstrap/regtest on x86_64-linux. Could somebody please
> > try it with SPEC to see if it doesn't cause performance regressions?
> >
> > 2008-10-20 Jakub Jelinek <jakub@redhat.com>
> >
> > PR tree-optimization/36038
> > * tree-ssa-loop-ivopts.c (add_old_iv_candidates): For pointer bases
> > add sizetype IV with initial value zero instead of pointer type.
> >
> > * gcc.c-torture/compile/pr36038.c: New test.
> >
> > --- gcc/tree-ssa-loop-ivopts.c.jj 2008-10-14 10:17:53.000000000 +0200
> > +++ gcc/tree-ssa-loop-ivopts.c 2008-10-20 15:33:31.000000000 +0200
> > @@ -2228,9 +2228,11 @@ add_old_iv_candidates (struct ivopts_dat
> > add_candidate (data, iv->base, iv->step, true, NULL);
> >
> > /* The same, but with initial value zero. */
> > - add_candidate (data,
> > - build_int_cst (TREE_TYPE (iv->base), 0),
> > - iv->step, true, NULL);
> > + if (POINTER_TYPE_P (TREE_TYPE (iv->base)))
> > + add_candidate (data, size_int (0), iv->step, true, NULL);
> > + else
> > + add_candidate (data, build_int_cst (TREE_TYPE (iv->base), 0),
> > + iv->step, true, NULL);
> >
> > phi = SSA_NAME_DEF_STMT (iv->ssa_name);
> > if (gimple_code (phi) == GIMPLE_PHI)
> > --- gcc/testsuite/gcc.c-torture/compile/pr36038.c.jj 2008-09-22 10:17:15.262001422 +0200
> > +++ gcc/testsuite/gcc.c-torture/compile/pr36038.c 2008-10-20 21:40:45.000000000 +0200
> > @@ -0,0 +1,43 @@
> > +/* PR tree-optimization/36038 */
> > +
> > +long long list[10];
> > +long long expect[10] = { 0, 1, 2, 3, 4, 4, 5, 6, 7, 9 };
> > +long long *stack_base;
> > +int indices[10];
> > +int *markstack_ptr;
> > +
> > +void
> > +doit (void)
> > +{
> > + long long *src;
> > + long long *dst;
> > + long long *sp = stack_base + 5;
> > + int diff = 2;
> > + int shift;
> > + int count;
> > +
> > + shift = diff - (markstack_ptr[-1] - markstack_ptr[-2]);
> > + count = (sp - stack_base) - markstack_ptr[-1] + 2;
> > + src = sp;
> > + dst = (sp += shift);
> > + while (--count)
> > + *dst-- = *src--;
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + int i;
> > + for (i = 0; i < 10; i++)
> > + list[i] = i;
> > +
> > + markstack_ptr = indices + 9;
> > + markstack_ptr[-1] = 2;
> > + markstack_ptr[-2] = 1;
> > +
> > + stack_base = list + 2;
> > + doit ();
> > + if (__builtin_memcmp (expect, list, sizeof (list)))
> > + __builtin_abort ();
> > + return 0;
> > +}
> >
> > Jakub
>