On Fri, Nov 19, 2021 at 7:34 AM apinski--- via Gcc-patches
<[email protected]> wrote:
>
> From: Andrew Pinski <[email protected]>
>
> There is some re-association code in fold_binary which conflicts with
> this optimization due keeping around some "constants" which are not
> INTEGER_CST (1 << -1) so we end up in an infinite loop because of that.
> So we need to limit this case to GIMPLE level only.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
OK.
Richard.
> PR tree-optimization/103314
>
> gcc/ChangeLog:
>
> * match.pd ((type) X op CST): Restrict the equal
> TYPE_PRECISION case to GIMPLE only.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.c-torture/compile/pr103314-1.c: New test.
> ---
> gcc/match.pd | 6 +++++-
> gcc/testsuite/gcc.c-torture/compile/pr103314-1.c | 6 ++++++
> 2 files changed, 11 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 4dc66fb47f2..24a84e3b504 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1619,7 +1619,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> after hoisting the conversion the operation will be narrower.
> It is also a good if the conversion is a nop as moves the
> conversion to one side; allowing for combining of the
> conversions. */
> - TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (type)
> + TYPE_PRECISION (TREE_TYPE (@0)) < TYPE_PRECISION (type)
> + /* The conversion check for being a nop can only be done at the
> gimple
> + level as fold_binary has some re-association code which can
> conflict
> + with this if there is a "constant" which is not a full
> INTEGER_CST. */
> + || (GIMPLE && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION
> (type))
> /* It's also a good idea if the conversion is to a non-integer
> mode. */
> || GET_MODE_CLASS (TYPE_MODE (type)) != MODE_INT
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
> b/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
> new file mode 100644
> index 00000000000..f4a63130421
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr103314-1.c
> @@ -0,0 +1,6 @@
> +/* { dg-options "" } */
> +int main() {
> + int t = 1;
> + unsigned c = 0, d1 = t ? 1 ^ c ^ 1 >> (-1) : 0; /* { dg-warning "is
> negative" } */
> + return d1;
> +}
> --
> 2.17.1
>
