[Bug target/93078] Missing fma and round functions auto-vectorization with x86-64 (sse2)

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93078

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-12-27
                 CC|                            |amonakov at gcc dot gnu.org
          Component|tree-optimization           |target
     Ever confirmed|0                           |1

--- Comment #1 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
> [...] not sure why dont auto-vectorize the function round directly to
> "roundps xmm0, XMMWORD PTR a[rip], 0"

This is because C round function is specified to use a non-standard rounding,
with halfway cases away from zero, not to nearest even. Hence a few extra
instructions to fix up halfway arguments.

For nearbyint, looks like CASE_CFN_NEARBYINT is not handled in
ix86_builtin_vectorized_function. Confirming for this case.