re PR other/56076 (Several 64-bit libgo tests FAIL in read_line_header)

	PR other/56076
runtime: Support sparc64 in lfstack.

From-SVN: r195479

libgo/runtime/lfstack.c

@@ -15,6 +15,15 @@
 # define PTR_BITS 32
 #endif
 #define PTR_MASK ((1ull<<PTR_BITS)-1)
+#define CNT_MASK (0ull-1)
+
+#if __SIZEOF_POINTER__ == 8 && defined(__sparc__)
+// SPARC64 uses all 64 bits of virtual addresses.  Use low-order three
+bits as ABA counter.
+#define PTR_BITS 0
+#define CNT_MASK 7
+#define PTR_MASK ((0ull-1)<<3)
+#endif
 
 void
 runtime_lfstackpush(uint64 *head, LFNode *node)
@@ -27,7 +36,7 @@ runtime_lfstackpush(uint64 *head, LFNode *node)
 	}
 
 	node->pushcnt++;
-	new = (uint64)(uintptr)node|(((uint64)node->pushcnt)<<PTR_BITS);
+	new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
 	old = runtime_atomicload64(head);
 	for(;;) {
 		node->next = (LFNode*)(uintptr)(old&PTR_MASK);
@@ -50,7 +59,7 @@ runtime_lfstackpop(uint64 *head)
 		node2 = runtime_atomicloadp(&node->next);
 		new = 0;
 		if(node2 != nil)
-			new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt)<<PTR_BITS);
+			new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
 		if(runtime_cas64(head, &old, new))
 			return node;
 	}