On Thu, Aug 10, 2023 at 2:21 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This was an oversight on my part not realizing that
> comparisons in generic can have a non-boolean type.
> This means if we have `(f < 0) | !(f < 0)` we would
> optimize this to -1 rather than just 1.
> This patch just adds the check for the type of the comparisons
> to be boolean type to keep the optimization in that case.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> PR 110954
>
> gcc/ChangeLog:
>
> * generic-match-head.cc (bitwise_inverted_equal_p): Check
> the type of the comparison to be boolean too.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.c-torture/execute/pr110954-1.c: New test.
> ---
> gcc/generic-match-head.cc | 3 ++-
> gcc/testsuite/gcc.c-torture/execute/pr110954-1.c | 10 ++++++++++
> 2 files changed, 12 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr110954-1.c
>
> diff --git a/gcc/generic-match-head.cc b/gcc/generic-match-head.cc
> index ddaf22f2179..ac2119bfdd0 100644
> --- a/gcc/generic-match-head.cc
> +++ b/gcc/generic-match-head.cc
> @@ -146,7 +146,8 @@ bitwise_inverted_equal_p (tree expr1, tree expr2)
> && bitwise_equal_p (expr1, TREE_OPERAND (expr2, 0)))
> return true;
> if (COMPARISON_CLASS_P (expr1)
> - && COMPARISON_CLASS_P (expr2))
> + && COMPARISON_CLASS_P (expr2)
> + && TREE_CODE (TREE_TYPE (expr1)) == BOOLEAN_TYPE)
in other places we restrict this to single-bit integral types instead which
covers a few more cases and also would handle BOOLEAN_TYPE
with either padding or non-padding extra bits correctly (IIRC fortran
has only padding bits but Ada has BOOLEAN_TYPEs with possibly
> 1 bit precision and arbitrary signedness - maybe even with custom
true/false values).
Richard.
> {
> tree op10 = TREE_OPERAND (expr1, 0);
> tree op20 = TREE_OPERAND (expr2, 0);
> diff --git a/gcc/testsuite/gcc.c-torture/execute/pr110954-1.c
> b/gcc/testsuite/gcc.c-torture/execute/pr110954-1.c
> new file mode 100644
> index 00000000000..8aad758e10f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/execute/pr110954-1.c
> @@ -0,0 +1,10 @@
> +
> +#define comparison (f < 0)
> +int main() {
> + int f = 0;
> + int d = comparison | !comparison;
> + if (d != 1)
> + __builtin_abort();
> + return 0;
> +}
> +
> --
> 2.31.1
>
