[Bug target/118384] unexpected call to __muldi3 generated for riscv target

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118384

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|c                           |target
             Target|                            |riscv32
   Last reconfirmed|                            |2025-01-09
           Keywords|                            |missed-optimization
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Must be some cost model issue:
```
unsigned long long f(unsigned long long a, unsigned long long b)
{
  unsigned long long c = -((a & 1) != 0);
  asm("":"+r"(c));
  return b & c;
}

unsigned long long f1(unsigned long long a, unsigned long long b)
{
  unsigned long long c = ((a & 1) != 0);
  return b * c;
}
```

Easy workaround:
Product += (a & 1) ? b : 0;