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Re: [PR70920] transform (intptr_t) x eq/ne CST to x eq/ne (typeof x) cst


On 29 July 2016 at 12:42, Richard Biener <rguenther@suse.de> wrote:
> On Fri, 29 Jul 2016, Prathamesh Kulkarni wrote:
>
>> On 28 July 2016 at 19:18, Richard Biener <rguenther@suse.de> wrote:
>> > On Thu, 28 Jul 2016, Prathamesh Kulkarni wrote:
>> >
>> >> On 28 July 2016 at 15:58, Andreas Schwab <schwab@suse.de> wrote:
>> >> > On Mo, Jul 25 2016, Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> wrote:
>> >> >
>> >> >> diff --git a/gcc/testsuite/gcc.dg/pr70920-4.c b/gcc/testsuite/gcc.dg/pr70920-4.c
>> >> >> new file mode 100644
>> >> >> index 0000000..dedb895
>> >> >> --- /dev/null
>> >> >> +++ b/gcc/testsuite/gcc.dg/pr70920-4.c
>> >> >> @@ -0,0 +1,21 @@
>> >> >> +/* { dg-do compile } */
>> >> >> +/* { dg-options "-O2 -fdump-tree-ccp-details -Wno-int-to-pointer-cast" } */
>> >> >> +
>> >> >> +#include <stdint.h>
>> >> >> +
>> >> >> +void f1();
>> >> >> +void f2();
>> >> >> +
>> >> >> +void
>> >> >> +foo (int a)
>> >> >> +{
>> >> >> +  void *cst = 0;
>> >> >> +  if ((int *) a == cst)
>> >> >> +    {
>> >> >> +      f1 ();
>> >> >> +      if (a)
>> >> >> +     f2 ();
>> >> >> +    }
>> >> >> +}
>> >> >> +
>> >> >> +/* { dg-final { scan-tree-dump "gimple_simplified to if \\(_\[0-9\]* == 0\\)" "ccp1" } } */
>> >> >
>> >> > This fails on all ilp32 platforms.
>> >> Oops, sorry for the breakage.
>> >> With -m32, the pattern is applied during forwprop1 rather than ccp1.
>> >> I wonder though why ccp1 fails to fold the pattern with -m32 ?
>> >> Looking at the dumps:
>> >>
>> >> without -m32:
>> >> input to ccp1 pass:
>> >>   <bb 2>:
>> >>   cst_4 = 0B;
>> >>   _1 = (long int) a_5(D);
>> >>   _2 = (void *) _1;
>> >>   if (cst_4 == _2)
>> >>     goto <bb 3>;
>> >>   else
>> >>     goto <bb 5>;
>> >>
>> >> cc1 pass dump shows:
>> >> Substituting values and folding statements
>> >>
>> >> Folding statement: _1 = (long int) a_5(D);
>> >> Not folded
>> >> Folding statement: _2 = (void *) _1;
>> >> Not folded
>> >> Folding statement: if (cst_4 == _2)
>> >> which is likely CONSTANT
>> >> Applying pattern match.pd:2537, gimple-match.c:6530
>> >> gimple_simplified to if (_1 == 0)
>> >> Folded into: if (_1 == 0)
>> >>
>> >> with -m32:
>> >> input to ccp1 pass:
>> >>  <bb 2>:
>> >>   cst_3 = 0B;
>> >>   a.0_1 = (void *) a_4(D);
>> >>   if (cst_3 == a.0_1)
>> >>     goto <bb 3>;
>> >>   else
>> >>     goto <bb 5>;
>> >>
>> >> ccp1 pass dump shows:
>> >> Substituting values and folding statements
>> >>
>> >> Folding statement: a.0_1 = (void *) a_4(D);
>> >> Not folded
>> >> Folding statement: if (cst_3 == a.0_1)
>> >> which is likely CONSTANT
>> >> Folded into: if (a.0_1 == 0B)
>> >>
>> >> I am not able to understand why it doesn't fold it to
>> >> if (a_4(D) == 0) ?
>> >> forwprop1 folds a.0_1 == 0B to a_4(D) == 0.
>> >
>> > It's because CCP folds with follow-single-use edges but the
>> > match-and-simplify code uses a single callback to valueize and
>> > decide whether its valid to follow the SSA edge.  I did have some
>> > old patches trying to fix that but never followed up on those.
>> Thanks for the explanation.
>> >
>> >> I suppose the test-case would need to scan ccp1 for non-ilp targets
>> >> and forwprop1 for
>> >> ilp targets. How do update the test-case to reflect this ?
>> >
>> > It's simpler to verify that at some point (forwprop) we have the
>> > expected IL rather than testing for the match debug prints.
>> In forwprop dump,
>> For m32, we have if (a_4(D) == 0)
>> and without m32: if (_1 == 0)
>> So need to match either a default def or anonymous name
>> in the test-case, which I am having a bit of trouble writing regex for.
>> In the patch i simply chose to match "== 0\\)", not sure if that's a good idea.
>> Also how do I update the test-case so that it gets tested twice, once with -m32
>> and once without ?
>
> I don't think just matching == 0 is a good idea.  I suggest to
> restrict the testcase to lp64 targets and maybe add a ilp32 variant.
Hi,
I restricted the test-case to lp64 targets.
Is this OK to commit ?

Thanks,
Prathamesh
>
> Richard.
>
>> Thanks,
>> Prathamesh
>> >
>> > Richard.
>> >
>> >> Thanks,
>> >> Prathamesh
>> >> >
>> >> > Andreas.
>> >> >
>> >> > --
>> >> > Andreas Schwab, SUSE Labs, schwab@suse.de
>> >> > GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
>> >> > "And now for something completely different."
>> >>
>> >>
>> >
>> > --
>> > Richard Biener <rguenther@suse.de>
>> > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
>>
>
> --
> Richard Biener <rguenther@suse.de>
> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)

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