On Sat, 29 Jan 2022, Jakub Jelinek wrote:
> On Fri, Jan 28, 2022 at 03:14:16PM -0700, Jeff Law via Gcc-patches wrote:
> > > This patch will add the missed pattern described in bug 103514 [1] to the
> > > match.pd. [1] includes proof of correctness for the patch too.
> > >
> > > PR tree-optimization/103514
> > > * match.pd (a & b) ^ (a == b) -> !(a | b): New optimization.
> > > * match.pd (a & b) == (a ^ b) -> !(a | b): New optimization.
> > > * gcc.dg/tree-ssa/pr103514.c: Testcase for this optimization.
> > >
> > > 1) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103514
> > Note the bug was filed an fixed during stage3, review just didn't happen in
> > a reasonable timeframe.
> >
> > I'm going to ACK this for the trunk and go ahead and commit it for you.
>
> The testcase FAILs on short-circuit targets like powerpc64le-linux.
> While the first 2 functions are identical, the last two look like:
> <bb 2> :
> if (a_5(D) != 0)
> goto <bb 3>; [INV]
> else
> goto <bb 4>; [INV]
>
> <bb 3> :
> if (b_6(D) != 0)
> goto <bb 5>; [INV]
> else
> goto <bb 4>; [INV]
>
> <bb 4> :
>
> <bb 5> :
> # iftmp.1_4 = PHI <1(3), 0(4)>
> _1 = a_5(D) == b_6(D);
> _2 = (int) _1;
> _3 = _2 ^ iftmp.1_4;
> _9 = _2 != iftmp.1_4;
> return _9;
> instead of the expected:
> <bb 2> :
> _3 = a_8(D) & b_9(D);
> _4 = (int) _3;
> _5 = a_8(D) == b_9(D);
> _6 = (int) _5;
> _1 = a_8(D) | b_9(D);
> _2 = ~_1;
> _7 = (int) _2;
> _10 = ~_1;
> return _10;
> so no wonder it doesn't match. E.g. x86_64-linux will also use jumps
> if it isn't just a && b but a && b && c && d (will do
> a & b and c & d tests and jump based on those.
>
> As it is too late to implement this optimization even for the short
> circuiting targets this late (not even sure which pass would be best),
> this patch just forces non-short-circuiting for the test.
>
> Tested on x86_64-linux -m32/-m64 and powerpc64le-linux, ok for trunk?
OK.
> 2022-01-29 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/103514
> * gcc.dg/tree-ssa/pr103514.c: Add
> --param logical-op-non-short-circuit=1 to dg-options.
>
> --- gcc/testsuite/gcc.dg/tree-ssa/pr103514.c.jj 2022-01-29
> 11:11:39.338627697 +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr103514.c 2022-01-29 17:37:18.255237211
> +0100
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-O -fdump-tree-optimized" } */
> +/* { dg-options "-O --param logical-op-non-short-circuit=1
> -fdump-tree-optimized" } */
> #include <stdbool.h>
>
> bool
> @@ -30,4 +30,4 @@ h (bool a, bool b)
> /* Make sure we have removed "==" and "^" and "&". */
> /* { dg-final { scan-tree-dump-not "&" "optimized"} } */
> /* { dg-final { scan-tree-dump-not "\\^" "optimized"} } */
> -/* { dg-final { scan-tree-dump-not "==" "optimized"} } */
> \ No newline at end of file
> +/* { dg-final { scan-tree-dump-not "==" "optimized"} } */
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
