diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 606af6e9ed5..159036699fb 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2000-01-04  David Edelsohn  <edelsohn@gnu.org>
+
+	* rs6000/sysv4.h (ASM_OUTPUT_DEF): Undefine.
+	(HANDLE_PRAGMA_PACK): Undefine.
+	(SLOW_UNALIGNED_ACCESS): Define.
+
 2000-01-04  David Edelsohn  <edelsohn@gnu.org>
 
 	* expmed.c (SLOW_UNALIGNED_ACCESS): Add mode and align parameters
diff --git a/gcc/config/rs6000/sysv4.h b/gcc/config/rs6000/sysv4.h
index b3d52e0e918..65b6cd5f104 100644
--- a/gcc/config/rs6000/sysv4.h
+++ b/gcc/config/rs6000/sysv4.h
@@ -350,13 +350,15 @@ do {									\
 
 /* Undefine some things which are defined by the generic svr4.h.  */
 
-#undef ASM_FILE_END
-#undef ASM_OUTPUT_EXTERNAL_LIBCALL
-#undef READONLY_DATA_SECTION
-#undef SELECT_SECTION
 #undef ASM_DECLARE_FUNCTION_NAME
+#undef ASM_FILE_END
 #undef ASM_OUTPUT_CONSTRUCTOR
 #undef ASM_OUTPUT_DESTRUCTOR
+#undef ASM_OUTPUT_DEF
+#undef ASM_OUTPUT_EXTERNAL_LIBCALL
+#undef HANDLE_PRAGMA_PACK
+#undef READONLY_DATA_SECTION
+#undef SELECT_SECTION
 
 /* Use the regular svr4 definitions.  */
 
@@ -397,6 +399,14 @@ do {									\
 #undef	STRICT_ALIGNMENT
 #define	STRICT_ALIGNMENT (TARGET_STRICT_ALIGN)
 
+/* Define this macro to be the value 1 if unaligned accesses have a cost
+   many times greater than aligned accesses, for example if they are
+   emulated in a trap handler.  */
+#define SLOW_UNALIGNED_ACCESS(MODE, ALIGN)			\
+   ((STRICT_ALIGNMENT						\
+     || (((MODE) == SFmode || (MODE) == DFmode || (MODE) == DImode) \
+         && (ALIGN) < 4)) ? 1 : 0)
+
 /* Alignment in bits of the stack boundary.  Note, in order to allow building
    one set of libraries with -mno-eabi instead of eabi libraries and non-eabi
    versions, just use 64 as the stack boundary.  */
diff --git a/gcc/tm.texi b/gcc/tm.texi
index 95a252b8b14..6a3ff5185d5 100644
--- a/gcc/tm.texi
+++ b/gcc/tm.texi
@@ -4731,7 +4731,9 @@ moves.  This can cause significantly more instructions to be produced.
 Therefore, do not set this macro non-zero if unaligned accesses only add a
 cycle or two to the time for a memory access.
 
-If the value of this macro is always zero, it need not be defined.
+If the value of this macro is always zero, it need not be defined.  If
+this macro is defined, it should produce a non-zero value when
+@code{STRICT_ALIGNMENT} is non-zero.
 
 @findex DONT_REDUCE_ADDR
 @item DONT_REDUCE_ADDR