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authorLinus Torvalds <torvalds@linux-foundation.org>2009-09-30 17:57:27 -0700
committerIngo Molnar <mingo@elte.hu>2009-10-01 08:01:08 +0200
commit982d007a6eec4a0abb404d2355eeec2c041c61ea (patch)
treec050631e7fbf5be10edb45ee3be0ded2670b7512 /arch/x86
parent84d88d5d4efc37dfb8a93a4a58d8a227ee86ffa4 (diff)
x86: Optimize cmpxchg64() at build-time some more
Try to avoid the 'alternates()' code when we can statically determine that cmpxchg8b is fine. We already have that CONFIG_x86_CMPXCHG64 (enabled by PAE support), and we could easily also enable it for some of the CPU cases. Note, this patch only adds CMPXCHG8B for the obvious Intel CPU's, not for others. (There was something really messy about cmpxchg8b and clone CPU's, so if you enable it on other CPUs later, do it carefully.) If we avoid that asm-alternative thing when we can assume the instruction exists, we'll generate less support crud, and we'll avoid the whole issue with that extra 'nop' for padding instruction sizes etc. LKML-Reference: <alpine.LFD.2.01.0909301743150.6996@localhost.localdomain> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/Kconfig.cpu3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 527519b8a9f..f2824fb8c79 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -400,7 +400,7 @@ config X86_TSC
config X86_CMPXCHG64
def_bool y
- depends on X86_PAE || X86_64
+ depends on X86_PAE || X86_64 || MCORE2 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MATOM
# this should be set for all -march=.. options where the compiler
# generates cmov.
@@ -412,6 +412,7 @@ config X86_MINIMUM_CPU_FAMILY
int
default "64" if X86_64
default "6" if X86_32 && X86_P6_NOP
+ default "5" if X86_32 && X86_CMPXCHG64
default "4" if X86_32 && (X86_XADD || X86_CMPXCHG || X86_BSWAP || X86_WP_WORKS_OK)
default "3"