AArch64: Tune case-values-threshold

Tune the case-values-threshold setting for modern cores.  A value of 11 improves
SPECINT2017 by 0.2% and reduces codesize by 0.04%.  With -Os use value 8 which
reduces codesize by 0.07%.

2021-10-18  Wilco Dijkstra  <wdijkstr@arm.com>

gcc/
	* config/aarch64/aarch64.c (aarch64_case_values_threshold):
	Change to 8 with -Os, 11 otherwise.

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 1d53c714ecde5e682335dbb1ec7294d58f987f42..674edd4e305463fcee996487d23e89cc53378a2f 100644 (file)
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -9500,8 +9500,8 @@ aarch64_cannot_force_const_mem (machine_mode mode ATTRIBUTE_UNUSED, rtx x)
    The expansion for a table switch is quite expensive due to the number
    of instructions, the table lookup and hard to predict indirect jump.
    When optimizing for speed, and -O3 enabled, use the per-core tuning if 
-   set, otherwise use tables for > 16 cases as a tradeoff between size and
-   performance.  When optimizing for size, use the default setting.  */
+   set, otherwise use tables for >= 11 cases as a tradeoff between size and
+   performance.  When optimizing for size, use 8 for smallest codesize.  */
 
 static unsigned int
 aarch64_case_values_threshold (void)
@@ -9512,7 +9512,7 @@ aarch64_case_values_threshold (void)
       && selected_cpu->tune->max_case_values != 0)
     return selected_cpu->tune->max_case_values;
   else
-    return optimize_size ? default_case_values_threshold () : 17;
+    return optimize_size ? 8 : 11;
 }
 
 /* Return true if register REGNO is a valid index register.