On Thu, Aug 24, 2023 at 9:16 PM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Now that MIN/MAX can sometimes be transformed into BIT_AND/BIT_IOR,
> we should allow BIT_AND and BIT_IOR in the early phiopt.
> Also we produce BIT_AND/BIT_IOR for things like `bool0 ? bool1 : 0`
> which seems like a good thing to allow early on too.
Hum.
I think if we allow AND/IOR we should also allow XOR and NOT.
Can you add dumping for replacements we disallow? I'm esp. curious
for those otherwise being "singleton". I know when doing early phiopt
I wanted to be very conservative (also to reduce testsuite fallout), and
I was mostly interested in MIN/MAX which I then extended to similar
things like ABS. But maybe we can revisit this if we understand which
cases we definitely do not want to do early?
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.cc (phiopt_early_allow): Allow
> BIT_AND_EXPR and BIT_IOR_EXPR.
> ---
> gcc/tree-ssa-phiopt.cc | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index 54706f4c7e7..7e63fb115db 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -469,6 +469,9 @@ phiopt_early_allow (gimple_seq &seq, gimple_match_op &op)
> {
> case MIN_EXPR:
> case MAX_EXPR:
> + /* MIN/MAX could be convert into these. */
> + case BIT_IOR_EXPR:
> + case BIT_AND_EXPR:
> case ABS_EXPR:
> case ABSU_EXPR:
> case NEGATE_EXPR:
> --
> 2.31.1
>
