PR go/56320
runtime: Support Solaris AMD64 in lfstack.
The address space layout is similar on SPARC64 and AMD64 when
running Solaris.
From-SVN: r196179
#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.
+#if __SIZEOF_POINTER__ == 8 && (defined(__sparc__) || (defined(__sun__) && defined(__amd64__)))
+// SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
+// Use low-order three bits as ABA counter.
+// http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
#undef PTR_BITS
#undef CNT_MASK
#undef PTR_MASK