[Qemu-devel] [6435] Massage PPC version of cpu_get_real_ticks a little

[malc]

Revision: 6435
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6435
Author:   malc
Date:     2009-01-25 10:56:48 +0000 (Sun, 25 Jan 2009)

Log Message:
-----------
Massage PPC version of cpu_get_real_ticks a little

Modified Paths:
--------------
    trunk/cpu-all.h

Modified: trunk/cpu-all.h
===================================================================
--- trunk/cpu-all.h     2009-01-24 20:19:18 UTC (rev 6434)
+++ trunk/cpu-all.h     2009-01-25 10:56:48 UTC (rev 6435)
@@ -996,30 +996,30 @@
 
 #if defined(_ARCH_PPC)
 
-static inline uint32_t get_tbl(void)
-{
-    uint32_t tbl;
-    asm volatile("mftb %0" : "=r" (tbl));
-    return tbl;
-}
-
-static inline uint32_t get_tbu(void)
-{
-       uint32_t tbl;
-       asm volatile("mftbu %0" : "=r" (tbl));
-       return tbl;
-}
-
 static inline int64_t cpu_get_real_ticks(void)
 {
-    uint32_t l, h, h1;
-    /* NOTE: we test if wrapping has occurred */
-    do {
-        h = get_tbu();
-        l = get_tbl();
-        h1 = get_tbu();
-    } while (h != h1);
-    return ((int64_t)h << 32) | l;
+    int64_t retval;
+#ifdef _ARCH_PPC64
+    /* This reads timebase in one 64bit go and includes Cell workaround from:
+       http://ozlabs.org/pipermail/linuxppc-dev/2006-October/027052.html
+     */
+    __asm__ __volatile__ (
+        "mftb    %0\n\t"
+        "cmpwi   %0,0\n\t"
+        "beq-    $-8"
+        : "=r" (retval));
+#else
+    /* http://ozlabs.org/pipermail/linuxppc-dev/1999-October/003889.html */
+    unsigned long junk;
+    __asm__ __volatile__ (
+        "mftbu   %1\n\t"
+        "mftb    %L0\n\t"
+        "mftbu   %0\n\t"
+        "cmpw    %0,%1\n\t"
+        "bne     $-16"
+        : "=r" (retval), "=r" (junk));
+#endif
+    return retval;
 }
 
 #elif defined(__i386__)