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

[Richard Biener <richard.guenther@gmail.com>]

> 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?

> 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
>