[Bug target/122935] Missed optimization: Optimize (a * b) ==/!= 0 to logical checks for signed/widening multiplications.

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122935

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-01-19

--- Comment #1 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Note that multiplers aren't *that* expensive on some designs; getting
multiplies down to 2c is possible if you're willing to burn the silicon.

I think Dongyan's suggestion is still a good one, but it's not going to be as
profitable as one might hope on some designs.

Also note you have to be careful with overflows here.