Hi,

Added an extra step to skip unusable epilogue modes when we know the 
target does not support predication. This uses a new function 
'support_predication_p' that is generated at build time and checks 
whether the target supports at least one optab that can be used for 
predicated code-generation.

Bootstrapped and regression tested on aarch64-none-linux-gnu.

OK for trunk?

gcc/ChangeLog:

         * tree-vect-loop.c (vect_better_loop_vinfo_p): Round factors up 
for epilogue costing.
         (vect_analyze_loop): Re-analyze all modes for epilogues, unless 
we are guaranteed that no
         predication is possible.
         (genopinit.c) (support_predication_p): Generate new function.

gcc/testsuite/ChangeLog:

         * gcc.target/aarch64/masked_epilogue.c: New test.