On Fri, Jul 22, 2022 at 11:10 PM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> > Am 22.07.2022 um 22:17 schrieb H.J. Lu via Gcc-patches
> > <gcc-patches@gcc.gnu.org>:
> >
> > On Thu, Jul 21, 2022 at 4:24 AM Richard Biener via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> >>
> >> The following makes sure to fold ~(a ^ b) to a == b for truth
> >> values (but not vectors, we'd have to check for vector support of
> >> equality). That turns the PR106379 testcase into a ranger one.
> >>
> >> Note that while we arrive at ~(a ^ b) in a convoluted way from
> >> original !a == !b one can eventually write the expression this
> >> way directly as well.
> >>
> >> Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
> >>
> >> PR tree-optimization/106379
> >> * match.pd (~(a ^ b) -> a == b): New pattern.
> >>
> >> * gcc.dg/pr106379-1.c: New testcase.
> >> ---
> >> gcc/match.pd | 6 ++++++
> >> gcc/testsuite/gcc.dg/pr106379-1.c | 9 +++++++++
> >> 2 files changed, 15 insertions(+)
> >> create mode 100644 gcc/testsuite/gcc.dg/pr106379-1.c
> >>
> >> diff --git a/gcc/match.pd b/gcc/match.pd
> >> index 8bbc0dbd5cd..88a1a5aa9cc 100644
> >> --- a/gcc/match.pd
> >> +++ b/gcc/match.pd
> >> @@ -1938,6 +1938,12 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >> (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
> >> (bit_not (bit_xor (view_convert @0) @1))))
> >>
> >> +/* ~(a ^ b) is a == b for truth valued a and b. */
> >> +(simplify
> >> + (bit_not (bit_xor:s truth_valued_p@0 truth_valued_p@1))
> >> + (if (!VECTOR_TYPE_P (type))
> >> + (convert (eq @0 @1))))
> >
> > For integers, isn't it wrong to convert ~(boolean exp) to boolean exp?
>
> That’s what the (convert. …) should compensate for?
Is ~(boolean exp) == ~((int) (boolean exp)) or (int) (~(boolean exp))?
> Richard
>
> >
> >> /* (x & ~m) | (y & m) -> ((x ^ y) & m) ^ x */
> >> (simplify
> >> (bit_ior:c (bit_and:cs @0 (bit_not @2)) (bit_and:cs @1 @2))
> >> diff --git a/gcc/testsuite/gcc.dg/pr106379-1.c
> >> b/gcc/testsuite/gcc.dg/pr106379-1.c
> >> new file mode 100644
> >> index 00000000000..7f2575e02dc
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr106379-1.c
> >> @@ -0,0 +1,9 @@
> >> +/* { dg-do compile } */
> >> +/* { dg-options "-O -fdump-tree-forwprop1" } */
> >> +
> >> +_Bool foo (_Bool a, _Bool b)
> >> +{
> >> + return !a == !b;
> >> +}
> >> +
> >> +/* { dg-final { scan-tree-dump "\[ab\]_\[0-9\]+\\(D\\) ==
> >> \[ba\]_\[0-9\]+\\(D\\)" "forwprop1" } } */
> >> --
> >> 2.35.3
> >
> >
> >
> > --
> > H.J.
--
H.J.
