[AArch64] Enable compare branch fusion

Enable the most basic form of compare-branch fusion since various CPUs
support it. This has no measurable effect on cores which don't support
branch fusion, but increases fusion opportunities on cores which do.

gcc/
	* config/aarch64/aarch64.c (generic_tunings): Add branch fusion.
	(neoversen1_tunings): Likewise.

gcc/ChangeLog

 2020-01-17  Wilco Dijkstra  <wdijkstr@arm.com>
 
+	* config/aarch64/aarch64.c (generic_tunings): Add branch fusion.
+	(neoversen1_tunings): Likewise.
+
+2020-01-17  Wilco Dijkstra  <wdijkstr@arm.com>
+
 	PR target/92692
 	* config/aarch64/aarch64.c (aarch64_split_compare_and_swap)
 	Add assert to ensure prolog has been emitted.

gcc/config/aarch64/aarch64.c

@@ -726,7 +726,7 @@ static const struct tune_params generic_tunings =
   SVE_NOT_IMPLEMENTED, /* sve_width  */
   4, /* memmov_cost  */
   2, /* issue_rate  */
-  (AARCH64_FUSE_AES_AESMC), /* fusible_ops  */
+  (AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_CMP_BRANCH), /* fusible_ops  */
   "16:12",	/* function_align.  */
   "4",	/* jump_align.  */
   "8",	/* loop_align.  */
@@ -1130,7 +1130,7 @@ static const struct tune_params neoversen1_tunings =
   SVE_NOT_IMPLEMENTED, /* sve_width  */
   4, /* memmov_cost  */
   3, /* issue_rate  */
-  AARCH64_FUSE_AES_AESMC, /* fusible_ops  */
+  (AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_CMP_BRANCH), /* fusible_ops  */
   "32:16",	/* function_align.  */
   "32:16",	/* jump_align.  */
   "32:16",	/* loop_align.  */