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[PR96791] disable POImode ld/st for memcpy [committed]

Message ID 20200911021617.47608-1-acsawdey@linux.ibm.com
State New
Headers show
Series [PR96791] disable POImode ld/st for memcpy [committed] | expand

Commit Message

Aaron Sawdey Sept. 11, 2020, 2:16 a.m. UTC 
This is a (hopefully temporary) fix to PR96791. This will make
the default be -mno-block-ops-vector-pair even on power10, so we will
not hit the issue of DSE trying to truncate a POImode register. I am
still concerned it will be possible to hit this because the MMA builtins
will also generate POImode stores, but I think any example of that will
be somewhat more contrived.

Bootstrap and regression tests passed on ppc64le power9.
Pre-approved by Segher, posting after commit.

gcc/ChangeLog:

	* config/rs6000/rs6000.c (rs6000_option_override_internal):
	Change default.
---
 gcc/config/rs6000/rs6000.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
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Patch

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f6a3ff6f089..9908830b07a 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -4020,10 +4020,11 @@  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)
-	rs6000_isa_flags |= OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
-      else
-	rs6000_isa_flags &= ~OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
+      /* When the POImode issues of PR96791 are resolved, then we can
+	 once again enable use of vector pair for memcpy/memmove on
+	 P10 if we have TARGET_MMA.  For now we make it disabled by
+	 default for all targets.  */
+      rs6000_isa_flags &= ~OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
     }
 
   /* Use long double size to select the appropriate long double.  We use