On Sun, Aug 9, 2026 at 8:04 AM Kael Andrew Alonzo Franco <[email protected]> wrote: > > Since r17-2886, GCC does a wrong optimize with: > > (a == b) & ((a|b) == 0) -> ((a|b) != 0) > (a != b) | ((a|b) != 0) -> ((a|b) == 0) > > Should be: > > (a == b) & ((a|b) == 0) -> ((a|b) == 0) > (a != b) | ((a|b) != 0) -> ((a|b) != 0) > > Regtest missed this because gcc.dg/int-bwise-opt-2.c only test: > > /* { dg-final { scan-tree-dump-times "a == b" 0 "optimized" } } */ > /* { dg-final { scan-tree-dump-times "a != b" 0 "optimized" } } */ > > Make this test more rigorous by comparing the final code. > > Bootstrapped and regtested on x86_64-pc-linux-gnu. > > PR middle-end/126742 > > gcc/ChangeLog: > > * match.pd: Fix wrong code. > > gcc/testsuite/ChangeLog: > > * gcc.dg/int-bwise-opt-2.c: Also test for PR126742.
Ok. > > Signed-off-by: Kael Andrew Franco <[email protected]> > --- > gcc/match.pd | 2 +- > gcc/testsuite/gcc.dg/int-bwise-opt-2.c | 15 +++++++++------ > 2 files changed, 10 insertions(+), 7 deletions(-) > > diff --git a/gcc/match.pd b/gcc/match.pd > index c2f411001a0..efaf0026711 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -7037,7 +7037,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (neeq @0 @1)) > (simplify > (bitop:c (eqne @0 @1) (eqne (bit_ior@2 @0 @1) integer_zerop@3)) > - (neeq @2 @3)) > + (eqne @2 @3)) > (simplify > (bitop (neeq @0 @1) (eqne (bit_ior @0 @1) integer_zerop)) > { constant_boolean_node (bitop == BIT_IOR_EXPR, type); }) > diff --git a/gcc/testsuite/gcc.dg/int-bwise-opt-2.c > b/gcc/testsuite/gcc.dg/int-bwise-opt-2.c > index cc1a48b061a..e0c065a54f3 100644 > --- a/gcc/testsuite/gcc.dg/int-bwise-opt-2.c > +++ b/gcc/testsuite/gcc.dg/int-bwise-opt-2.c > @@ -1,15 +1,18 @@ > /* { dg-do compile } */ > /* { dg-options "-O2 -fdump-tree-optimized" } */ > > -int f1(int a, int b) > +_Bool > +a_ne_b_bit_ior (int a, int b) > { > - return (a != b) | ((a | b) != 0); > + _Bool ret = ((a | b) != 0); > + return (((a != b) | ret) == ret); > } > > -int f2(int a, int b) > +_Bool > +a_eq_b_bit_and (int a, int b) > { > - return (a == b) & ((a | b) == 0); > + _Bool ret = ((a | b) == 0); > + return (((a == b) & ret) == ret); > } > > - /* { dg-final { scan-tree-dump-times "a == b" 0 "optimized" } } */ > - /* { dg-final { scan-tree-dump-times "a != b" 0 "optimized" } } */ > +/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */ > -- > 2.55.0 >
