From: Aaron Sawdey <acsawdey@linux.ibm.com>
Date: Thu, 10 Sep 2020 20:12:49 +0000 (-0500)
Subject: [PATCH][PR96791] disable POImode ld/st for memcpy
X-Git-Tag: upstream/12.2.0~13823
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=848e74bea1e8031925d3efe2d85b555a3cf8db38;p=platform%2Fupstream%2Fgcc.git

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

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.

gcc/ChangeLog:

	* config/rs6000/rs6000.c (rs6000_option_override_internal):
	Change default.
---

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f6a3ff6..9908830 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