[PATCH] x86_64 : prefetchw() can fall back to prefetch() if !3DNOW
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 <[EMAIL PROTECTED]>
--- linux-2.6.13-rc3/include/asm-x86_64/processor.h 2005-07-13
06:46:46.000000000 +0200
+++ linux-2.6.13-rc3-ed/include/asm-x86_64/processor.h 2005-07-28
18:47:39.000000000 +0200
@@ -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));
