Changeset 6653 in vbox

Timestamp:

Jan 31, 2008 12:13:00 PM (17 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

27719

Message:

Yet another fix for ASMAtomicCmpXchgExU64, needed by 32bit gcc with
debug build, to prevent gcc from running out of registers.

File:

• trunk/include/iprt/asm.h (modified) (1 diff)

trunk/include/iprt/asm.h

@@ -2602 +2602 @@
     uint64_t u64Ret;
 #   if defined(PIC) || defined(RT_OS_DARWIN) /* darwin: 4.0.1 compiler option / bug? */
-    __asm__ __volatile__("xchgl %%ebx, %2\n\t"
-                         "lock; cmpxchg8b %4\n\t"
-                         "xchgl %%ebx, %2\n\t"
-                         : "=A" (u64Ret),
-                           "=m" (*pu64)
+    /* NB: this code uses a memory clobber description, because the clean
+     * solution with an output value for *pu64 makes gcc run out of registers.
+     * This will cause suboptimal code, and anyone with a better solution is
+     * welcome to improve this. */
+    __asm__ __volatile__("xchgl %%ebx, %1\n\t"
+                         "lock; cmpxchg8b %3\n\t"
+                         "xchgl %%ebx, %1\n\t"
+                         : "=A" (u64Ret)
                          : "DS" ((uint32_t)u64New),
                            "c" ((uint32_t)(u64New >> 32)),
                            "m" (*pu64),
-                           "0" (u64Old));
+                           "0" (u64Old)
+                         : "memory" );
 #   else /* !PIC */
     __asm__ __volatile__("lock; cmpxchg8b %4\n\t"