Re: [RFC] current changes vs 2.4.15-pre4

[Benjamin LaHaise]

Hello,

Slight update since, as Manfred pointed out, the Pentium and i486 leave the 
upper bits of the register undefined.  Later intel docs claim the upper 
bits are zeroed, but I don't know what to believe anymore.  Also, removing 
the inline asm that was a silly idea lets gcc generate better code:

c0106008:       0f 00 c8                str    %ax
...
c0106012:       25 e0 ff 00 00          and    $0xffe0,%eax
...
c0106023:       8b 34 c5 40 25 3c c0    mov    0xc03c2540(,%eax,8),%esi

As Alan says: "x86 is really just an instruction stream compression format".

		-ben

diff -ur tr.prev/include/asm-i386/smp.h tr-2.4.15-pre4/include/asm-i386/smp.h
--- tr.prev/include/asm-i386/smp.h	Tue Nov 13 15:00:40 2001
+++ tr-2.4.15-pre4/include/asm-i386/smp.h	Tue Nov 13 15:19:39 2001
@@ -117,7 +117,7 @@
 	 * function calls.  Fun!  -ben
 	 */
 	__asm__ ("str %w0" : "=r" (tr) : "m" (dummy_cpu_id));
-	return tr;
+	return tr & 0xffe0;	/* Pentiums leave the high bits undefined. */
 }
 
 #define smp_processor_id()	( (get_TR() >> 5) - (__FIRST_TSS_ENTRY >> 2) )
@@ -128,13 +128,8 @@
  */
 #define smp_per_cpu_data()	\
 	( (struct per_cpu_data *)					\
-	  ({	long idx;						\
-		__asm__("str %w0 ; shll %1,%0"				\
-			: "=r" (idx)					\
-			: "i" (LOG2_PER_CPU_SIZE - 5)			\
-			, "m" (dummy_cpu_id));				\
-		(long)&aligned_data + idx -				\
-			(__FIRST_TSS_ENTRY << (LOG2_PER_CPU_SIZE - 2)); }) )
+	  ( (get_TR() << (LOG2_PER_CPU_SIZE - 5)) + (long)&aligned_data \
+		- (__FIRST_TSS_ENTRY << (LOG2_PER_CPU_SIZE - 2)) ) )
 
 static __inline int hard_smp_processor_id(void)
 {