[Xen-devel] [PATCH 01/17] xen: x86 & generic: change to __builtin_prefetch()

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

Quoting Andi Kleen in Linux b483570a13be from 2007:
    gcc 3.2+ supports __builtin_prefetch, so it's possible to use it on all
    architectures. Change the generic fallback in linux/prefetch.h to use it
    instead of noping it out. gcc should do the right thing when the
    architecture doesn't support prefetching

    Undefine the x86-64 inline assembler version and use the fallback.

ARM wants to use the builtins.

Fix a pair of spelling errors, one of which was from Lucas De Marchi in the
Linux tree.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/include/xen/prefetch.h |   13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/xen/include/xen/prefetch.h b/xen/include/xen/prefetch.h
index 8d7d3ff..ba73998 100644
--- a/xen/include/xen/prefetch.h
+++ b/xen/include/xen/prefetch.h
@@ -28,24 +28,17 @@
        prefetchw(x)    - prefetches the cacheline at "x" for write
        spin_lock_prefetch(x) - prefectches the spinlock *x for taking
        
-       there is also PREFETCH_STRIDE which is the architecure-prefered 
+       there is also PREFETCH_STRIDE which is the architecture-preferred
        "lookahead" size for prefetching streamed operations.
        
 */
 
-/*
- *     These cannot be do{}while(0) macros. See the mental gymnastics in
- *     the loop macro.
- */
- 
 #ifndef ARCH_HAS_PREFETCH
-#define ARCH_HAS_PREFETCH
-static inline void prefetch(const void *x) {;}
+#define prefetch(x) __builtin_prefetch(x)
 #endif
 
 #ifndef ARCH_HAS_PREFETCHW
-#define ARCH_HAS_PREFETCHW
-static inline void prefetchw(const void *x) {;}
+#define prefetchw(x) __builtin_prefetch(x,1)
 #endif
 
 #ifndef ARCH_HAS_SPINLOCK_PREFETCH
-- 
1.7.10.4


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