[Qemu-devel] testandset asm fix

[Paul Brook]

The inline assembly used for the x86/x86-64 host testandset routine is bogus.
The operand constraints are wrong (Fails to compile at -O0).
Also the return value is incorrect. It should return 0 if the lock was 
successfully acquired. 

Patch below fixes it. The additional sete test is unnecessary, we can just use 
the comparison/writeback value.

Paul

Index: exec-all.h
===================================================================
RCS file: /cvsroot/qemu/qemu/exec-all.h,v
retrieving revision 1.26
diff -u -p -r1.26 exec-all.h
--- exec-all.h 10 Jan 2005 23:23:48 -0000 1.26
+++ exec-all.h 6 Feb 2005 14:35:43 -0000
@@ -392,28 +392,24 @@ static inline int testandset (int *p)
 #ifdef __i386__
 static inline int testandset (int *p)
 {
-    char ret;
-    long int readval;
-    
-    __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
-                          : "=q" (ret), "=m" (*p), "=a" (readval)
-                          : "r" (1), "m" (*p), "a" (0)
-                          : "memory");
-    return ret;
+    long int readval = 0;
+
+    __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
+                          : "+m" (*p), "+a" (readval)
+                          : "r" (1));
+    return readval;
 }
 #endif
 
 #ifdef __x86_64__
 static inline int testandset (int *p)
 {
-    char ret;
-    int readval;
-    
-    __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
-                          : "=q" (ret), "=m" (*p), "=a" (readval)
-                          : "r" (1), "m" (*p), "a" (0)
-                          : "memory");
-    return ret;
+    long int readval = 0;
+
+    __asm__ __volatile__ ("lock; cmpxchgl %2, %0"
+                          : "+m" (*p), "+a" (readval)
+                          : "r" (1));
+    return readval;
 }
 #endif