svn commit: r358672 - head/lib/libc/powerpc64/string

[Alfredo Dal'Ava Junior]

Author: alfredo
Date: Thu Mar  5 14:13:22 2020
New Revision: 358672
URL: https://svnweb.freebsd.org/changeset/base/358672

Log:
  [PowerPC64] restrict memcpy/bcopy optimization to POWER ISA >=V2.07
  
  VSX instructions were added in POWER ISA V2.06 (POWER7), but it
  requires data to be word-aligned. Such requirement was removed in
  ISA V2.07B (POWER8).
  
  Since current memcpy/bcopy optimization relies on VSX instructions
  handling misalignment transparently, and kernel doesn't currently
  implement an alignment error handler, this optimzation should be
  restrict to ISA V2.07 onwards.
  
  SIGBUS on stxvd2x instruction was reproduced in POWER7+ CPU.
  
  Reviewed by:	luporl, jhibbits, bdragon
  Approved by:	jhibbits (mentor)
  Differential Revision:	https://reviews.freebsd.org/D23958

Modified:
  head/lib/libc/powerpc64/string/bcopy_resolver.c

Modified: head/lib/libc/powerpc64/string/bcopy_resolver.c
==============================================================================
--- head/lib/libc/powerpc64/string/bcopy_resolver.c	Thu Mar  5 14:05:22 2020	(r358671)
+++ head/lib/libc/powerpc64/string/bcopy_resolver.c	Thu Mar  5 14:13:22 2020	(r358672)
@@ -61,7 +61,12 @@ FN_RET FN_NAME_VSX FN_PARAMS;
 
 DEFINE_UIFUNC(, FN_RET, FN_NAME, FN_PARAMS)
 {
-	if (cpu_features & PPC_FEATURE_HAS_VSX)
+	/* VSX instructions were added in POWER ISA 2.06,
+	 * however it requires data to be word-aligned.
+	 * Since POWER ISA 2.07B this is solved transparently
+	 * by the hardware
+	 */
+	if (cpu_features2 & PPC_FEATURE2_ARCH_2_07)
 		return (FN_NAME_VSX);
 	else
 		return (FN_NAME_NOVSX);