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?
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
