[gcc(refs/users/meissner/heads/work074)] Use absolute switch table addresses for zero cycle moves.

[gcc(refs/users/meissner/heads/work074)] Use absolute switch table addresses for zero cycle moves.

[Michael Meissner]

https://gcc.gnu.org/g:bb4ce9da05773298a139c72b4a89f5fe15fbd1c8

commit bb4ce9da05773298a139c72b4a89f5fe15fbd1c8
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Mon Nov 15 19:51:56 2021 -0500

    Use absolute switch table addresses for zero cycle moves.
    
    This option enables using absolute addresses in switch tables if the
    power10 zero cycle move tuning is turned on.  The combination of using
    absolute addresses in switch tables along with zero cycle moves seems to
    give the best performance.
    
    2021-11-15  Michael Meissner  <meissner@the-meissners.org>
    
            * config/rs6000/rs6000.c (rs6000_option_override_internal): Use
            absolute addresses in switch tables if power10 zero cycle move
            fusion is enabled.

Diff:
---
 gcc/config/rs6000/rs6000.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 8531cef0337..dc942765828 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -4502,6 +4502,12 @@ rs6000_option_override_internal (bool global_init_p)
       && (rs6000_isa_flags_explicit & OPTION_MASK_P10_FUSION_ZERO_CYCLE) == 0)
     rs6000_isa_flags |= OPTION_MASK_P10_FUSION_ZERO_CYCLE;
 
+  /* If we enable zero cycle move fusion, also switch to absolute addresses in
+     switch tables.  */
+  if (TARGET_P10_FUSION && TARGET_P10_FUSION_ZERO_CYCLE
+      && !global_options_set.x_rs6000_relative_jumptables)
+    rs6000_relative_jumptables = 0;
+
   /* Turn off vector pair/mma options on non-power10 systems.  */
   else if (!TARGET_POWER10 && TARGET_MMA)
     {