linux-kernel - [PATCH v3 6/6] x86, asm/rwsem: Use named operands in __downgrade

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Date:   Tue, 19 Sep 2017 18:37:45 -0500
From:   Miguel Bernal Marin <miguel.bernal.marin@...ux.intel.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH v3 6/6] x86, asm/rwsem: Use named operands in __downgrade_write()

Since GCC version 3.1, it is possible to specify input and output
operands using symbolic names which can be referenced within the
assembler code.

Convert to named operands makes easy to understand and maintain for
future changes.

Signed-off-by: Miguel Bernal Marin <miguel.bernal.marin@...ux.intel.com>
---
 arch/x86/include/asm/rwsem.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index 3245902e961f..1f5d083599ba 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -208,7 +208,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
 	register void *__sp asm(_ASM_SP);
 
 	asm volatile("# beginning __downgrade_write\n\t"
-		     LOCK_PREFIX _ASM_ADD "%3,(%2)\n\t"
+		     LOCK_PREFIX _ASM_ADD "%[inc],(%[sem])\n\t"
 		     /*
 		      * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386)
 		      *     0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64)
@@ -218,7 +218,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
 		     "1:\n\t"
 		     "# ending __downgrade_write\n"
 		     : "+m" (sem->count), "+r" (__sp)
-		     : "a" (sem), "er" (-RWSEM_WAITING_BIAS)
+		     : [sem] "a" (sem), [inc] "er" (-RWSEM_WAITING_BIAS)
 		     : "memory", "cc");
 }
 
-- 
2.14.1