(TSL_SET): backport from db3.

db2/mutex/alpha.gcc

@@ -1,52 +1,24 @@
 /*
- * @(#)alpha.gcc	10.1 (Sleepycat) 4/12/97
- *
- * The code appearing below is taken from Richard L. Sites, ed.  "Alpha
- * Architecture Reference Manual", Digital Press, 1992, page 5-7 and 5-8.
- * There are 2 modifications:
- *
- * 1. The jump from blbs __r1,30f to !__r1, which is dictated by the way the
- * TSL_SET macro is used.  The code suggested in Sites includes the main loop
- * of the spin lock, whereas in this code the rest the loop is specified in C.
- * The generated code might be suboptimal if the compiler generates a forward
- * branch for the usual case in which the mutex is uncontested.
- *
- * 2. At label 20, Sites suggests including code for testing for an excessive
- * number of _processor_ lock conflicts.  (The seq_c instruction stores its
- * first argument provided that no other processor has written to a byte range
- * including its memory-location argument.)  Absent such checking the code
- * below could conceivably stall silently on a multiprocessor alpha, depending
- * on how often processor/processor conflicts occur in a particular byte range.
- *
- * Note that the mb ("memory-barrier") instruction in TSL_UNSET is critical to
- * correct operation in a multiprocessor alpha (as is, of course, the mb in
- * the TSL_SET macro).  Without the mb, changes to shared memory that occurred
- * inside the critical section (before the TSL_UNSET) might reach shared memory
- * _after_ the change of tsl to 0, thereby permitting another processor to see
- * an inconsistent view of the data protected by the mutex.
+ * @(#)alpha.gcc	11.1 (Sleepycat) 8/30/99
  *
  * For gcc/alpha, 0 is clear, 1 is set.
  */
-#define TSL_SET(tsl) ({							\
+#ifdef __GNUC__
+#define	TSL_SET(tsl) ({							\
 	register tsl_t *__l = (tsl);					\
-	register tsl_t __r1, __r2;					\
-	__asm__ volatile("						\n\
-	   10: ldq_l %0,(%2)						\n\
-	       blbs  %0,30f						\n\
-	       or    %0,1,%1						\n\
-	       stq_c %1,(%2)						\n\
-	       beq   %1,20f						\n\
-	       mb							\n\
-	       br    30f						\n\
-	   20: br    10b						\n\
-	   30: "							\
-	  : "=&r" (__r1), "=&r" (__r2)					\
-	  : "r" (__l));							\
-	!__r1;								\
+	int __r;							\
+	asm volatile(							\
+		"1:	ldl_l	%0,%1\n"				\
+		"	blbs	%0,2f\n"				\
+		"	mov	1,%0\n"					\
+		"	stl_c	%0,%1\n"				\
+		"	bne	%0,1b\n"				\
+		"	mb\n"						\
+		"2:"							\
+		: "=&r"(__r), "=m"(*__l) : "m"(*__l) : "memory");	\
+	__r;								\
 })
+#endif
 
-#define TSL_UNSET(tsl) ({						\
-	register tsl_t *__l = (tsl);					\
-	__asm__ volatile("mb; stq $31,(%0);" : : "r" (__l));		\
-})
+#define	TSL_UNSET(tsl)	(*(tsl) = 0)
 #define	TSL_INIT(tsl)	TSL_UNSET(tsl)