diff --git a/acconfig.h b/acconfig.h
index 5c8dbcb49edcfa33eb9a872ad27ef2c5f4a610ef..d77c28956623f9fd8c7e4a2e146e236eb026a173 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -59,6 +59,15 @@
 /* Define to unsigned long long int if <sys/types.h> doesn't define */
 #undef ullong
 
+/* Define to alignment constraint on doubles or on unsigned int - whichever is the greater */
+#undef ALIGNMENT_DOUBLE
+
+/* Define to alignment constraint on floats or on unsigned int - whichever is the greater */
+#undef ALIGNMENT_FLOAT
+
+/* Define to alignment constraint on unsigned int - whichever is the greater */
+#undef ALIGNMENT_UNSIGNED_INT
+
 
 /* Leave that blank line there!!  Autoheader needs it.
    If you're adding to this file, keep in mind:
diff --git a/aclocal.m4 b/aclocal.m4
index 0535dc10725007715758d1b3304493b182a7de31..d1f9a6436481997e10a85e92d7dd692ed36d68c3 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1,4 +1,4 @@
-# $Id: aclocal.m4,v 1.19 1998/03/03 04:45:07 reid Exp $
+# $Id: aclocal.m4,v 1.20 1998/03/03 19:04:48 reid Exp $
 #
 # Extra autoconf macros for the Glasgow fptools
 #
@@ -340,3 +340,45 @@ else
 fi
 rm -fr conftest*
 ])
+
+dnl ** figure out whether types can be word-aligned
+dnl    (test based on test in smalltalk-1.1.5 configuration)
+dnl    (required SIZEOF test but AC_CHECK_SIZEOF doesn't call PROVIDE
+dnl     so we can't call REQUIRE)
+
+dnl GHC_CHECK_ALIGNMENT(TYPE)
+AC_DEFUN(GHC_CHECK_ALIGNMENT,
+[changequote(<<, >>)dnl
+dnl The name to #define.
+define(<<AC_TYPE_NAME>>, translit(alignment_$1, [a-z *], [A-Z_P]))dnl
+dnl The cache variable name.
+define(<<AC_CV_NAME>>, translit(ac_cv_alignment_$1, [ *], [_p]))dnl
+dnl The name of the corresponding size.
+define(<<AC_CV_SIZEOF_NAME>>, translit(ac_cv_sizeof_$1, [ *], [_p]))dnl
+changequote([, ])dnl
+AC_MSG_CHECKING(alignment of $1)
+AC_CACHE_VAL(AC_CV_NAME,
+[AC_TRY_RUN([
+main()
+{
+    unsigned int vec[3];
+    $1 test, *testptr;
+
+    test = *($1 *)&vec[1];
+    testptr = ($1 *)&vec[1];
+    *testptr = test;
+
+    exit(0);
+}
+],
+AC_CV_NAME=$ac_cv_sizeof_unsigned_int,
+AC_CV_NAME=$AC_CV_SIZEOF_NAME,
+AC_CV_NAME=$AC_CV_SIZEOF_NAME)])
+AC_MSG_RESULT($AC_CV_NAME)
+AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME)
+AC_PROVIDE($AC_TYPE_NAME)
+undefine([AC_TYPE_NAME])dnl
+undefine([AC_CV_NAME])dnl
+undefine([AC_CV_SIZEOF_NAME])dnl
+])
+
diff --git a/configure.in b/configure.in
index 7487fc9a8c7d29e89d0e2b1c68c4293715e30bba..f14eab27453c19d20974dc969cf2735151728807 100644
--- a/configure.in
+++ b/configure.in
@@ -443,13 +443,24 @@ dnl ** how do we get a timezone name, and UTC offset ?
 AC_STRUCT_TIMEZONE
 
 # 
-dnl what's the type of timezone?
+dnl ** what's the type of timezone?
 AC_TYPE_TIMEZONE
 
 #
-dnl do we have altzone?
+dnl ** do we have altzone?
 AC_ALTZONE
 
+dnl ** what are the sizes of various types
+dnl    (these must come before GHC_CHECK_ALIGNMENT)
+AC_CHECK_SIZEOF(unsigned int,4)
+AC_CHECK_SIZEOF(float,4)
+AC_CHECK_SIZEOF(double,8)
+
+dnl ** what are alignment constraints on various types
+GHC_CHECK_ALIGNMENT(unsigned int) dnl redundant but harmless
+GHC_CHECK_ALIGNMENT(float)
+GHC_CHECK_ALIGNMENT(double)
+
 #
 dnl ** check for specific library functions that we are interested in
 #