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Re: [PR70920] transform (intptr_t) x eq/ne CST to x eq/ne (typeof x) cst
On July 29, 2016 4:32:40 PM GMT+02:00, Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> wrote:
>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 ?
OK
Thanks,
Richard.
>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)