Commit 79337628 authored by Andy Polyakov's avatar Andy Polyakov
Browse files

crypto/x86_64cpuid.pl: suppress AVX512F flag on Skylake-X. 



It was observed that AVX512 code paths can negatively affect overall
Skylake-X system performance. But we are talking specifically about
512-bit code, while AVX512VL, 256-bit variant of AVX512F instructions,
is supposed to fly as smooth as AVX2. Which is why it remains unmasked.

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4838)
parent 05de3a5b

crypto/x86_64cpuid.pl

+8 −0
Original line number Diff line number Diff line
@@ -139,6 +139,7 @@ OPENSSL_ia32_cpuid: 
.Lnocacheinfo:

	mov	\$1,%eax

	cpuid

	movd	%eax,%xmm0		# put aside processor id

	and	\$0xbfefffff,%edx	# force reserved bits to 0

	cmp	\$0,%r9d

	jne	.Lnotintel
@@ -186,6 +187,13 @@ OPENSSL_ia32_cpuid: 
	jc	.Lnotknights

	and	\$0xfff7ffff,%ebx	# clear ADCX/ADOX flag

.Lnotknights:

	movd	%xmm0,%eax		# restore processor id

	and	\$0x0fff0ff0,%eax

	cmp	\$0x00050650,%eax	# Skylake-X

	jne	.Lnotskylakex

	and	\$0xfffeffff,%ebx	# ~(1<<16)

					# suppress AVX512F flag on Skylake-X

.Lnotskylakex:

	mov	%ebx,8(%rdi)		# save extended feature flags

	mov	%ecx,12(%rdi)

.Lno_extended_info: