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[PowerPC64] restrict memcpy/bcopy optimization to POWER ISA >=V2.07

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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
This commit is contained in:
Alfredo Dal'Ava Junior 2020-03-05 14:13:22 +00:00
parent 5554f4cc45
commit 2b37373c48
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=358672
1 changed files with 6 additions and 1 deletions
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7
lib/libc/powerpc64/string/bcopy_resolver.c
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@ -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);