diff --git a/js/src/jstypes.h b/js/src/jstypes.h
index c2103d80b34..3df17bb3e69 100644
--- a/js/src/jstypes.h
+++ b/js/src/jstypes.h
@@ -323,11 +323,21 @@
 #  define JS_64BIT
 # endif
 #elif defined(__GNUC__)
-# ifdef __x86_64__
+/* Additional GCC defines are when running on Solaris, AIX, and HPUX */
+# if defined(__x86_64__) || defined(__sparcv9) || \
+        defined(__64BIT__) || defined(__LP64__)
 #  define JS_64BIT
 # endif
-#elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
-# ifdef __x86_64
+#elif defined(__SUNPRO_C) || defined(__SUNPRO_CC) /* Sun Studio C/C++ */
+# if defined(__x86_64) || defined(__sparcv9)
+#  define JS_64BIT
+# endif
+#elif defined(__xlc__) || defined(__xlC__)        /* IBM XL C/C++ */
+# if defined(__64BIT__)
+#  define JS_64BIT
+# endif
+#elif defined(__HP_cc) || defined(__HP_aCC)       /* HP-UX cc/aCC */
+# if defined(__LP64__)
 #  define JS_64BIT
 # endif
 #else