From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Wed, 3 Sep 2014 13:09:06 +0000 (+0200)
Subject: x86/current: provide additional information to optimise get_cpu_info()
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~4483^2~1
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=df0ae94fd56d5f9c64089364efecb1793442360b;p=xen.git

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@citrix.com>
---

diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index 2081015ff9..b95fd79698 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)