arm64: cmpxchg: avoid "cc" clobber in ll/sc routines

We can perform the cmpxchg comparison using eor and cbnz which avoids
the "cc" clobber for the ll/sc case and consequently for the LSE case
where we may have to fall-back on the ll/sc code at runtime.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
index f3cb1052ab24..a3d21e7cee4f 100644
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -166,7 +166,7 @@ static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
 	"	mov	%w[ret], w30")
 	: [ret] "+r" (x0), [v] "+Q" (ptr->counter)
 	: [old] "r" (w1), [new] "r" (w2)
-	: "x30", "cc", "memory");
+	: "x30", "memory");
 
 	return x0;
 }
@@ -313,7 +313,7 @@ static inline long atomic64_cmpxchg(atomic64_t *ptr, long old, long new)
 	"	mov	%[ret], x30")
 	: [ret] "+r" (x0), [v] "+Q" (ptr->counter)
 	: [old] "r" (x1), [new] "r" (x2)
-	: "x30", "cc", "memory");
+	: "x30", "memory");
 
 	return x0;
 }