Samuel Thibault
2007-Nov-23 15:58 UTC
[Xen-devel] [PATCH] [Mini-OS] Optimize get_current()
Let gcc perform the computation with SP itself, leading to yet better
code.
diff -r 2e05a6173be0 extras/mini-os/include/x86/arch_sched.h
--- a/extras/mini-os/include/x86/arch_sched.h Fri Nov 23 11:58:11 2007 +0000
+++ b/extras/mini-os/include/x86/arch_sched.h Fri Nov 23 15:53:18 2007 +0000
@@ -7,10 +7,11 @@
{
struct thread **current;
#ifdef __i386__
- __asm__("andl %%esp,%0; ":"=r" (current) :
"0" (~8191UL));
+ register unsigned long sp asm("esp");
#else
- __asm__("andq %%rsp,%0; ":"=r" (current) :
"0" (~8191UL));
+ register unsigned long sp asm("rsp");
#endif
+ current = (void *)(sp & ~8191UL);
return *current;
}
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