[PATCH] x86_64: prefetchw() can fall back to prefetch() if !3DNOW
This is a multi-part message in MIME format. If the cpu lacks 3DNOW
feature, we can use a normal prefetcht0 instruction instead of NOP5.
"prefetchw (%rxx)" and "prefetcht0 (%rxx)" have the same length, ranging
from 3 to 5 bytes depending on the register. So this patch even helps
AMD64, shortening the length of the code.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-x86_64/processor.h b/include/asm-x86_64/processor.h
index 194160f..a832199 100644
--- a/include/asm-x86_64/processor.h
+++ b/include/asm-x86_64/processor.h
@@ -398,7 +398,7 @@
#define ARCH_HAS_PREFETCHW 1
static inline void prefetchw(void *x)
{
- alternative_input(ASM_NOP5,
+ alternative_input("prefetcht0 (%1)",
"prefetchw (%1)",
X86_FEATURE_3DNOW,
"r" (x));