centos5 gcc 4.1 asm bug

include/atomic/x86-gcc.h:
  force %esi register, don't give gcc a choice.
  (otherwise it could choose %ebx, and 4.1 did)

cmake/os/Linux.cmake

@@ -47,9 +47,3 @@ IF(HAVE_DECL_SHM_HUGETLB)
   SET(HAVE_LARGE_PAGE_OPTION 1)
 ENDIF()
 
-IF(CMAKE_SIZEOF_VOID_P EQUAL 4 AND CMAKE_SYSTEM_PROCESSOR MATCHES "86")
-  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=i686")
-  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=i686")
-  SET(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -march=i686")
-ENDIF()
-

include/atomic/x86-gcc.h

@@ -124,10 +124,10 @@
   asm volatile ("push %%ebx;"                                     \
                 "movl (%%ecx), %%ebx;"                            \
                 "movl 4(%%ecx), %%ecx;"                           \
-                LOCK_prefix "; cmpxchg8b %0;"                     \
+                LOCK_prefix "; cmpxchg8b (%%esi);"                \
                 "setz %2; pop %%ebx"                              \
-                : "=m" (*a), "+A" (*cmp), "=c" (ret)              \
-                : "c" (&set), "m" (*a)                            \
+                : "+S" (a), "+A" (*cmp), "=c" (ret)               \
+                : "c" (&set)                                      \
                 : "memory", "esp")
 #endif