[Xen-changelog] [xen master] x86/current: provide additional information to optimise get_cpu_info()

[patchbot@xxxxxxx]

commit df0ae94fd56d5f9c64089364efecb1793442360b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Sep 3 15:09:06 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Sep 3 15:09:06 2014 +0200

    x86/current: provide additional information to optimise get_cpu_info()
    
    Exactly as with c/s d55c5eefe "x86: use compiler visible "add" instead of
    inline assembly "or" in get_cpu_info()", this is achieved by providing more
    information to the compiler.
    
    This causes a net drop of almost 4K of .text
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/include/asm-x86/current.h |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index 2081015..b95fd79 100644
--- a/xen/include/asm-x86/current.h
+++ b/xen/include/asm-x86/current.h
@@ -25,9 +25,9 @@ struct cpu_info {
 
 static inline struct cpu_info *get_cpu_info(void)
 {
-    unsigned long tos;
-    __asm__ ( "and %%rsp,%0" : "=r" (tos) : "0" (~(STACK_SIZE-1)) );
-    return (struct cpu_info *)(tos + STACK_SIZE) - 1;
+    register unsigned long sp asm("rsp");
+
+    return (struct cpu_info *)((sp & ~(STACK_SIZE-1)) + STACK_SIZE) - 1;
 }
 
 #define get_current()         (get_cpu_info()->current_vcpu)
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog