Re: [PATCH] Fix PR110726: a | (a == b) can sometimes produce wrong code

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

On Wed, Jul 19, 2023 at 3:53 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> So I had missed/forgot that EQ_EXPR could have an non boolean
> type for generic when I implemented r14-2556-g0407ae8a7732d9.
> This patch adds check for one bit precision intergal type
> which fixes the problem.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
>         PR tree-optimization/110726
>
> gcc/ChangeLog:
>
>         * match.pd ((a|b)&(a==b),a|(a==b),(a&b)|(a==b)):
>         Add checks to make sure the type was one bit precision
>         intergal type.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.c-torture/execute/bitops-1.c: New test.
> ---
>  gcc/match.pd                                  | 12 +++++--
>  .../gcc.c-torture/execute/bitops-1.c          | 33 +++++++++++++++++++
>  2 files changed, 42 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.c-torture/execute/bitops-1.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 054e6585876..4dfe92623f7 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1229,7 +1229,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  /* (a | b) & (a == b)  -->  a & b (boolean version of the above).  */
>  (simplify
>   (bit_and:c (bit_ior @0 @1) (nop_convert? (eq:c @0 @1)))
> - (bit_and @0 @1))
> + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))

that's really a constraint on 'type', not sure if it would be clearer
to test that.
What's the nop_convert you've seen in practice here?  With integer comparison
result shouldn't those be convert? instead?

> +      && TYPE_PRECISION (TREE_TYPE (@0)) == 1)
> +  (bit_and @0 @1)))
>
>  /* a | ~(a ^ b)  -->  a | ~b  */
>  (simplify
> @@ -1239,7 +1241,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  /* a | (a == b)  -->  a | (b^1) (boolean version of the above). */
>  (simplify
>   (bit_ior:c @0 (nop_convert? (eq:c @0 @1)))
> - (bit_ior @0 (bit_xor @1 { build_one_cst (type); })))
> + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
> +      && TYPE_PRECISION (TREE_TYPE (@0)) == 1)
> +  (bit_ior @0 (bit_xor @1 { build_one_cst (type); }))))
>
>  /* (a | b) | (a &^ b)  -->  a | b  */
>  (for op (bit_and bit_xor)
> @@ -1255,7 +1259,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>  /* (a & b) | (a == b)  -->  a == b  */
>  (simplify
>   (bit_ior:c (bit_and:c @0 @1) (nop_convert?@2 (eq @0 @1)))
> - @2)
> + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
> +      && TYPE_PRECISION (TREE_TYPE (@0)) == 1)
> +  @2))
>
>  /* ~(~a & b)  -->  a | ~b  */
>  (simplify
> diff --git a/gcc/testsuite/gcc.c-torture/execute/bitops-1.c b/gcc/testsuite/gcc.c-torture/execute/bitops-1.c
> new file mode 100644
> index 00000000000..cfaa6b9fd26
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/execute/bitops-1.c
> @@ -0,0 +1,33 @@
> +/* PR tree-optimization/110726 */
> +
> +#define DECLS(n,VOL)                   \
> +__attribute__((noinline,noclone))      \
> +int h##n(VOL int A, VOL int B){                \
> +    return (A | B) & (A == B);         \
> +}                                      \
> +__attribute__((noinline,noclone))      \
> +int i##n(VOL int A, VOL int B){                \
> +    return A | (A == B);               \
> +}                                      \
> +__attribute__((noinline,noclone))      \
> +int k##n(VOL int A, VOL int B){                \
> +    return (A & B) | (A == B);         \
> +}                                      \
> +
> +DECLS(0,)
> +DECLS(1,volatile)
> +
> +int values[] = { 0, 1, 2, 3, -1, -2, -3, 0x10080 };
> +int numvalues = sizeof(values)/sizeof(values[0]);
> +
> +int main(){
> +    for(int A = 0; A < numvalues; A++)
> +      for(int B = 0; B < numvalues; B++)
> +       {
> +         int a = values[A];
> +         int b = values[B];
> +         if (h0 (a, b) != h1 (a, b)) __builtin_abort();
> +         if (i0 (a, b) != i1 (a, b)) __builtin_abort();
> +         if (k0 (a, b) != k1 (a, b)) __builtin_abort();
> +       }
> +}
> --
> 2.31.1
>