--- src/lisp.h
+++ src/lisp.h	2010-10-18 13:46:05.240426350 +0000
@@ -375,7 +375,7 @@ enum pvec_type
  For example, if tem is a Lisp_Object whose type is Lisp_Cons,
  XCONS (tem) is the struct Lisp_Cons * pointing to the memory for that cons.  */
 
-#ifndef USE_LISP_UNION_TYPE
+#if !defined(USE_LISP_UNION_TYPE) && !defined(__s390x__)
 
 /* Return a perfect hash of the Lisp_Object representation.  */
 #define XHASH(a) (a)
@@ -385,19 +385,31 @@ enum pvec_type
 #define TYPEMASK ((((EMACS_INT) 1) << GCTYPEBITS) - 1)
 #define XTYPE(a) ((enum Lisp_Type) (((EMACS_UINT) (a)) & TYPEMASK))
 #ifdef USE_2_TAGS_FOR_INTS
+#ifndef XINT
 # define XINT(a) (((EMACS_INT) (a)) >> (GCTYPEBITS - 1))
+#endif
+#ifndef XUINT
 # define XUINT(a) (((EMACS_UINT) (a)) >> (GCTYPEBITS - 1))
+#endif
 # define make_number(N) (((EMACS_INT) (N)) << (GCTYPEBITS - 1))
 #else
+#ifndef XINT
 # define XINT(a) (((EMACS_INT) (a)) >> GCTYPEBITS)
+#endif
+#ifndef XUINT
 # define XUINT(a) (((EMACS_UINT) (a)) >> GCTYPEBITS)
+#endif
 # define make_number(N) (((EMACS_INT) (N)) << GCTYPEBITS)
 #endif
+#ifndef XSET
 #define XSET(var, type, ptr)					\
     (eassert (XTYPE (ptr) == 0), /* Check alignment.  */	\
      (var) = ((EMACS_INT) (type)) | ((EMACS_INT) (ptr)))
+#endif
 
+#ifndef XPNTR
 #define XPNTR(a) ((EMACS_INT) ((a) & ~TYPEMASK))
+#endif
 
 #else  /* not USE_LSB_TAG */
 
@@ -418,19 +430,29 @@ enum pvec_type
 /* Extract the value of a Lisp_Object as a (un)signed integer.  */
 
 #ifdef USE_2_TAGS_FOR_INTS
+#ifndef XINT
 # define XINT(a) ((((EMACS_INT) (a)) << (GCTYPEBITS - 1)) >> (GCTYPEBITS - 1))
+#endif
+#ifndef XUINT
 # define XUINT(a) ((EMACS_UINT) ((a) & (1 + (VALMASK << 1))))
+#endif
 # define make_number(N) ((((EMACS_INT) (N)) & (1 + (VALMASK << 1))))
 #else
+#ifndef XINT
 # define XINT(a) ((((EMACS_INT) (a)) << (BITS_PER_EMACS_INT - VALBITS))	\
 		 >> (BITS_PER_EMACS_INT - VALBITS))
+#endif
+#ifndef XUINT
 # define XUINT(a) ((EMACS_UINT) ((a) & VALMASK))
+#endif
 # define make_number(N)		\
   ((((EMACS_INT) (N)) & VALMASK) | ((EMACS_INT) Lisp_Int) << VALBITS)
 #endif
 
+#ifndef XSET
 #define XSET(var, type, ptr) \
    ((var) = ((EMACS_INT)(type) << VALBITS) + ((EMACS_INT) (ptr) & VALMASK))
+#endif
 
 #define XPNTR(a) ((EMACS_UINT) ((a) & VALMASK))
 
@@ -457,14 +479,18 @@ enum pvec_type
 #define XINT(a) ((a).s.val)
 #endif /* EXPLICIT_SIGN_EXTEND */
 
+#ifndef XUINT
 #define XUINT(a) ((a).u.val)
+#endif
 
 #ifdef USE_LSB_TAG
 
+#ifndef XSET
 # define XSET(var, vartype, ptr) \
   (eassert ((((EMACS_UINT) (ptr)) & ((1 << GCTYPEBITS) - 1)) == 0),	\
    (var).u.val = ((EMACS_UINT) (ptr)) >> GCTYPEBITS,			\
    (var).u.type = ((char) (vartype)))
+#endif
 
 /* Some versions of gcc seem to consider the bitfield width when issuing
    the "cast to pointer from integer of different size" warning, so the
@@ -479,8 +505,10 @@ enum pvec_type
 # define XFASTINT(a) ((a).i + 0)
 # define XSETFASTINT(a, b) ((a).i = (b))
 
+#ifndef XSET
 # define XSET(var, vartype, ptr) \
    (((var).s.val = ((EMACS_INT) (ptr))), ((var).s.type = ((char) (vartype))))
+#endif
 
 #endif	/* !USE_LSB_TAG */
 
--- src/m/ibms390x.h
+++ src/m/ibms390x.h	2009-08-11 12:47:07.000000000 +0000
@@ -78,7 +78,9 @@ NOTE-END */
    working alloca function and it should be used.  Undefine it if an
    assembler-language alloca in the file alloca.s should be used. */
 
+#ifndef HAVE_ALLOCA
 #define HAVE_ALLOCA
+#endif
 
 /* On the 64 bit architecture, we can use 60 bits for addresses */