Re: [PATCH] Fix 100864: `(a&!b) | b` is not opimized to `a | b` for comparisons

[Andrew Pinski <pinskia@gmail.com>]

On Sun, Jul 23, 2023 at 1:39 AM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> > Am 23.07.2023 um 01:27 schrieb Andrew Pinski via Gcc-patches <gcc-patches@gcc.gnu.org>:
> >
> > This adds a special case of the `(a&~b) | b` pattern where
> > `b` and `~b` are comparisons.
> >
> > OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> Don’t we have an existing match for inversion s we could amend?

We don't currently but I might be able to pattern the function off of
what was similarly done for bitwise_equal_p .
I noticed the patch which added bitwise_equal_p even could benefit
from this similar thing.

Thanks,
Andrew

>
> > gcc/ChangeLog:
> >
> >    PR tree-optimization/100864
> >    * match.pd ((~x & y) | x -> x | y): Add comparison variant.
> >
> > gcc/testsuite/ChangeLog:
> >
> >    * gcc.dg/tree-ssa/bitops-3.c: New test.
> > ---
> > gcc/match.pd                             | 17 +++++-
> > gcc/testsuite/gcc.dg/tree-ssa/bitops-3.c | 67 ++++++++++++++++++++++++
> > 2 files changed, 83 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bitops-3.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index bfd15d6cd4a..dd4a2df537d 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -1928,7 +1928,22 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >  /* (~x & y) | x -> x | y */
> >  (simplify
> >   (bitop:c (rbitop:c (bit_not @0) @1) @0)
> > -  (bitop @0 @1)))
> > +  (bitop @0 @1))
> > + /* Similar but for comparisons which have been inverted already,
> > +    Note it is hard to simulate the inverted tcc_comparison due
> > +    NaNs; That is == and != are sometimes inversions and sometimes not.
> > +    So a double for loop is needed and then compare the inverse code
> > +    with the result of invert_tree_comparison is needed.
> > +    This works fine for vector compares as -1 and 0 are bitwise
> > +    inverses.  */
> > + (for cmp (tcc_comparison)
> > +  (for icmp (tcc_comparison)
> > +   (simplify
> > +    (bitop:c (rbitop:c (icmp @0 @1) @2) (cmp@3 @0 @1))
> > +     (with { enum tree_code ic = invert_tree_comparison
> > +             (cmp, HONOR_NANS (@0)); }
> > +      (if (ic == icmp)
> > +       (bitop @3 @2)))))))
> >
> > /* ((x | y) & z) | x -> (z & y) | x */
> > (simplify
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bitops-3.c b/gcc/testsuite/gcc.dg/tree-ssa/bitops-3.c
> > new file mode 100644
> > index 00000000000..68fff4edce9
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bitops-3.c
> > @@ -0,0 +1,67 @@
> > +/* PR tree-optimization/100864 */
> > +
> > +/* { dg-do run } */
> > +/* { dg-options "-O1 -fdump-tree-optimized-raw" } */
> > +
> > +#define op_ne !=
> > +#define op_eq ==
> > +#define op_lt <
> > +#define op_le <=
> > +#define op_gt >
> > +#define op_ge >=
> > +
> > +#define operators(t) \
> > +t(ne) \
> > +t(eq) \
> > +t(lt) \
> > +t(le) \
> > +t(gt) \
> > +t(ge)
> > +
> > +#define cmpfunc(v, op) \
> > +__attribute__((noipa)) \
> > +_Bool func_##op##_##v(v int a, v int b, v _Bool e) \
> > +{ \
> > +  v _Bool c = (a op_##op b); \
> > +  v _Bool d = !c; \
> > +  return (e & d) | c; \
> > +}
> > +
> > +#define cmp_funcs(op) \
> > +cmpfunc(, op) \
> > +cmpfunc(volatile , op)
> > +
> > +operators(cmp_funcs)
> > +
> > +#define test(op) \
> > +if (func_##op##_ (a, b, e) != func_##op##_volatile (a, b, e)) \
> > + __builtin_abort();
> > +
> > +int main()
> > +{
> > +  for(int a = -3; a <= 3; a++)
> > +    for(int b = -3; b <= 3; b++)
> > +      {
> > +    _Bool e = 0;
> > +    operators(test)
> > +    e = 1;
> > +    operators(test)
> > +      }
> > +  return 0;
> > +}
> > +
> > +/* Check to make sure we optimize `(a&!b) | b` -> `a | b`. */
> > +/* There are 6 different comparison operators testing here. */
> > +/* bit_not_expr and bit_and_expr should show up for each one (volatile). */
> > +/* Each operator should show up twice
> > +   (except for `!=` which shows up 2*6 (each tester) + 2 (the 2 loops) extra = 16). */
> > +/* bit_ior_expr will show up for each operator twice (non-volatile and volatile). */
> > +/* { dg-final { scan-tree-dump-times "ne_expr,"      16 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "eq_expr,"       2 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "lt_expr,"       2 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "le_expr,"       2 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "gt_expr,"       2 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "ge_expr,"       2 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "bit_not_expr,"  6 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "bit_and_expr,"  6 "optimized"} } */
> > +/* { dg-final { scan-tree-dump-times "bit_ior_expr," 12 "optimized"} } */
> > \ No newline at end of file
> > --
> > 2.31.1
> >