linux-kernel - [PATCH v3 4/6] x86, asm/rwsem: Use named operands in __up

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Date:   Tue, 19 Sep 2017 18:37:43 -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 4/6] x86, asm/rwsem: Use named operands in __up_read()

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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index 8400ad3e17dc..2b3fb6d316f5 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -169,14 +169,14 @@ static inline void __up_read(struct rw_semaphore *sem)
 	register void *__sp asm(_ASM_SP);
 
 	asm volatile("# beginning __up_read\n\t"
-		     LOCK_PREFIX "  xadd      %1,(%3)\n\t"
+		     LOCK_PREFIX "  xadd      %[tmp],(%[sem])\n\t"
 		     /* subtracts 1, returns the old value */
 		     "  jns        1f\n\t"
 		     "  call call_rwsem_wake\n" /* expects old value in %edx */
 		     "1:\n"
 		     "# ending __up_read\n"
-		     : "+m" (sem->count), "=d" (tmp), "+r" (__sp)
-		     : "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
+		     : "+m" (sem->count), [tmp] "=d" (tmp), "+r" (__sp)
+		     : [sem] "a" (sem), "[tmp]" (-RWSEM_ACTIVE_READ_BIAS)
 		     : "memory", "cc");
 }
 
-- 
2.14.1