[PATCH] i386: generate better code around descriptor update and acces…

…s functions

GCC can generate better code around descriptor update and access functions
when there is not an explicit "eax" register constraint.

Testing: You won't boot if this is messed up, since the TSS descriptor will be
corrupted.  Verified the assembler and booted.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-i386/desc.h

@@ -27,8 +27,8 @@ struct Xgt_desc_struct {
 
 extern struct Xgt_desc_struct idt_descr, cpu_gdt_descr[NR_CPUS];
 
-#define load_TR_desc() __asm__ __volatile__("ltr %%ax"::"a" (GDT_ENTRY_TSS*8))
-#define load_LDT_desc() __asm__ __volatile__("lldt %%ax"::"a" (GDT_ENTRY_LDT*8))
+#define load_TR_desc() __asm__ __volatile__("ltr %w0"::"q" (GDT_ENTRY_TSS*8))
+#define load_LDT_desc() __asm__ __volatile__("lldt %w0"::"q" (GDT_ENTRY_LDT*8))
 
 #define load_gdt(dtr) __asm__ __volatile("lgdt %0"::"m" (*dtr))
 #define load_idt(dtr) __asm__ __volatile("lidt %0"::"m" (*dtr))
@@ -49,14 +49,14 @@ extern void set_intr_gate(unsigned int irq, void * addr);
 
 #define _set_tssldt_desc(n,addr,limit,type) \
 __asm__ __volatile__ ("movw %w3,0(%2)\n\t" \
-	"movw %%ax,2(%2)\n\t" \
-	"rorl $16,%%eax\n\t" \
-	"movb %%al,4(%2)\n\t" \
+	"movw %w1,2(%2)\n\t" \
+	"rorl $16,%1\n\t" \
+	"movb %b1,4(%2)\n\t" \
 	"movb %4,5(%2)\n\t" \
 	"movb $0,6(%2)\n\t" \
-	"movb %%ah,7(%2)\n\t" \
-	"rorl $16,%%eax" \
-	: "=m"(*(n)) : "a" (addr), "r"(n), "ir"(limit), "i"(type))
+	"movb %h1,7(%2)\n\t" \
+	"rorl $16,%1" \
+	: "=m"(*(n)) : "q" (addr), "r"(n), "ir"(limit), "i"(type))
 
 static inline void __set_tss_desc(unsigned int cpu, unsigned int entry, void *addr)
 {