[Bug target/63277] ARM - NEON excessive use of vmov for vtbl2 / uint8x8x2 for shuffling data unnecessarily around

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63277

ktkachov at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Target|                            |arm
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-09-16
                 CC|                            |ktkachov at gcc dot gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |5.0

--- Comment #1 from ktkachov at gcc dot gnu.org ---
Confirmed.

The vmovs and vswp are generated from the implementation of our vcombine. The
define_insn_and split for neon_vcombine<mode> splits into moves/swaps after
reload, thus not giving the register allocator a chance to optimise the moves
away.