[Bug tree-optimization/94908] Failure to optimally optimize certain shuffle patterns

[gabravier at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94908

--- Comment #3 from Gabriel Ravier  ---
Looks like this gives much better output now.

[Bug tree-optimization/94908] Failure to optimally optimize certain shuffle patterns

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94908

Richard Biener  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2020-05-04
 Ever confirmed|0   |1

--- Comment #2 from Richard Biener  ---
Hmm, ideally it would be extract g()[1], insert at a[0].  But yes, we're not
trying to split an not handled suffle into two but leave that for targets
to sort out ... (x86 has code for many 3-insn shuffles for example).

[Bug tree-optimization/94908] Failure to optimally optimize certain shuffle patterns

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94908

--- Comment #1 from Marc Glisse  ---
Even if we write __builtin_shuffle, the vector lowering pass turns it into the
same code (constructor of BIT_FIELD_REFs), which seems to indicate that the
target does not handle this pattern.