s390/spinlock: use R constraint in inline assembly

hcahca · hcahca · commit 4f9abb7e70f2 · 2021-04-12T12:46:43.000+02:00
Allow the compiler to generate slightly better code by using the R
constraint.

Signed-off-by: Heiko Carstens &lt;hca@linux.ibm.com&gt;
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
@@ -88,7 +88,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lp)
 	asm_inline volatile(
 		ALTERNATIVE("", ".long 0xb2fa0070", 49)	/* NIAI 7 */
 		"	sth	%1,%0\n"
-		: "=Q" (((unsigned short *) &lp->lock)[1])
+		: "=R" (((unsigned short *) &lp->lock)[1])
 		: "d" (0) : "cc", "memory");
 }
 

Original file line number	Diff line number	Diff line change
`@@ -88,7 +88,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lp)`
`88`	`88`	`asm_inline volatile(`
`89`	`89`	`ALTERNATIVE("", ".long 0xb2fa0070", 49) /* NIAI 7 */`
`90`	`90`	`" sth %1,%0\n"`
`91`		`- : "=Q" (((unsigned short *) &lp->lock)[1])`
	`91`	`+ : "=R" (((unsigned short *) &lp->lock)[1])`
`92`	`92`	`: "d" (0) : "cc", "memory");`
`93`	`93`	`}`
`94`	`94`