[PATCH] x86_64 : support atomic ops with 64 bits integer values

Mathieu Desnoyers
2008-08-16T07:39:38Z

x86_64 add/sub atomic ops does not seems to accept integer values bigger
than 32 bits as immediates. Intel's add/sub documentation specifies they
have to be passed as registers.

http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Machine-Constraints.html#Machine-Constraints

states :

e
32-bit signed integer constant, or a symbolic reference known to fit that range (for immediate operands in sign-extending x86-64 instructions).
Z
32-bit unsigned integer constant, or a symbolic reference known to fit that range (for immediate operands in zero-extending x86-64 instructions).

Since add/sub does sign extension, using the "e" constraint seems appropriate.

It applies to 2.6.27-rc, 2.6.26, 2.6.25...

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@elte.hu>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Joe Perches <joe@perches.com>
---
include/asm-x86/atomic_64.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux-2.6-lttng/include/asm-x86/atomic_64.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86/atomic_64.h 2008-08-16 03:19:35.000000000 -0400
+++ linux-2.6-lttng/include/asm-x86/atomic_64.h 2008-08-16 03:21:18.000000000 -0400
@@ -228,7 +228,7 @@ static inline void atomic64_add(long i,
{
asm volatile(LOCK_PREFIX "addq %1,%0"
: "=m" (v->counter)
- : "ir" (i), "m" (v->counter));
+ : "er" (i), "m" (v->counter));
}

/**
@@ -242,7 +242,7 @@ static inline void atomic64_sub(long i,
{
asm volatile(LOCK_PREFIX "subq %1,%0"
: "=m" (v->counter)
- : "ir" (i), "m" (v->counter));
+ : "er" (i), "m" (v->counter));
}

/**
@@ -260,7 +260,7 @@ static inline int atomic64_sub_and_test(

asm volatile(LOCK_PREFIX "subq %2,%0; sete %1"
: "=m" (v->counter), "=qm" (c)
- : "ir" (i), "m" (v->counter) : "memory");
+ : "er" (i), "m" (v->counter) : "memory");
return c;
}

@@ -341,7 +341,7 @@ static inline int atomic64_add_negative(

asm volatile(LOCK_PREFIX "addq %2,%0; sets %1"
: "=m" (v->counter), "=qm" (c)
- : "ir" (i), "m" (v->counter) : "memory");
+ : "er" (i), "m" (v->counter) : "memory");
return c;
}

--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68