[PATCH][AArch64] PR79262: Adjust vector cost

[Wilco Dijkstra]

PR79262 has been fixed for almost all AArch64 cpus, however the example is still
vectorized in a few cases, resulting in lower performance.  Increase the cost of
vector-to-scalar moves so it is more similar to the other vector costs. As a result
-mcpu=cortex-a53 no longer vectorizes the testcase - libquantum and SPECv6
performance improves.

OK for commit?

ChangeLog:
2018-01-22  Wilco Dijkstra  <wdijkstr@arm.com>

        PR target/79262
        * config/aarch64/aarch64.c (generic_vector_cost): Adjust vec_to_scalar_cost.
--

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index c6a83c881038873d8b68e36f906783be63ddde56..43f5b7162152ca92a916f4febee01f624c375202 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -403,7 +403,7 @@ static const struct cpu_vector_cost generic_vector_cost =
   1, /* vec_int_stmt_cost  */
   1, /* vec_fp_stmt_cost  */
   2, /* vec_permute_cost  */
-  1, /* vec_to_scalar_cost  */
+  2, /* vec_to_scalar_cost  */
   1, /* scalar_to_vec_cost  */
   1, /* vec_align_load_cost  */
   1, /* vec_unalign_load_cost  */