[AArch64] Increase default function alignment

With -mcpu=generic the function alignment is currently 8, however almost all
supported cores prefer 16 or higher, so increase the default to 16:12.
This gives ~0.2% performance increase on SPECINT2017, while codesize is 0.12%
larger.

    gcc/
	* config/aarch64/aarch64.c (generic_tunings): Set function alignment to
	16:12.

From-SVN: r274374

gcc/ChangeLog

+2019-08-13  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	* config/aarch64/aarch64.c (generic_tunings): Set function alignment to
+	16:12.
+
 2019-08-13  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
 
 	* config/msp430/driver-msp430.c (msp430_set_driver_var): New.

gcc/config/aarch64/aarch64.c

@@ -712,7 +712,7 @@ static const struct tune_params generic_tunings =
   4, /* memmov_cost  */
   2, /* issue_rate  */
   (AARCH64_FUSE_AES_AESMC), /* fusible_ops  */
-  "8",	/* function_align.  */
+  "16:12",	/* function_align.  */
   "4",	/* jump_align.  */
   "8",	/* loop_align.  */
   2,	/* int_reassoc_width.  */