[BACKPORT] Disable generating load/store vector pairs for block copies.

Testing has found that using load and store vector pair for block copies
can result in a slow down on power10.  This patch disables using the
vector pair instructions for block copies if we are tuning for power10.

2022-06-11   Michael Meissner  <meissner@linux.ibm.com>

gcc/

	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Do
	not generate block copies with vector pair instructions if we are
	tuning for power10.  Back port from master branch.

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 4030864..040487b 100644 (file)
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -4151,7 +4151,10 @@ rs6000_option_override_internal (bool global_init_p)
 
   if (!(rs6000_isa_flags_explicit & OPTION_MASK_BLOCK_OPS_VECTOR_PAIR))
     {
-      if (TARGET_MMA && TARGET_EFFICIENT_UNALIGNED_VSX)
+      /* Do not generate lxvp and stxvp on power10 since there are some
+        performance issues.  */
+      if (TARGET_MMA && TARGET_EFFICIENT_UNALIGNED_VSX
+         && rs6000_tune != PROCESSOR_POWER10)
        rs6000_isa_flags |= OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
       else
        rs6000_isa_flags &= ~OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;