diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,15 @@
 # Changelog for [`integer-gmp` package](http://hackage.haskell.org/package/integer-gmp)
 
+## 1.0.0.1  *Feb 2016*
+
+  * Bundled with GHC 8.0.1
+
+  * Optimise `bitBigNat`/`bigInteger`
+
+  * Fix minor issue in `eqBigNatWord#`
+
+  * Various minor optimisations
+
 ## 1.0.0.0  *Mar 2015*
 
   * Bundled with GHC 7.10.1
diff --git a/configure b/configure
--- a/configure
+++ b/configure
@@ -676,6 +676,7 @@
 docdir
 oldincludedir
 includedir
+runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -698,7 +699,6 @@
 ac_subst_files=''
 ac_user_opts='
 enable_option_checking
-with_cc
 with_gmp_includes
 with_gmp_libraries
 with_gmp_framework_preferred
@@ -751,6 +751,7 @@
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
+runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -1003,6 +1004,15 @@
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
+  -runstatedir | --runstatedir | --runstatedi | --runstated \
+  | --runstate | --runstat | --runsta | --runst | --runs \
+  | --run | --ru | --r)
+    ac_prev=runstatedir ;;
+  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
+  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
+  | --run=* | --ru=* | --r=*)
+    runstatedir=$ac_optarg ;;
+
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1140,7 +1150,7 @@
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir
+		libdir localedir mandir runstatedir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -1293,6 +1303,7 @@
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
+  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]
@@ -1326,7 +1337,6 @@
 Optional Packages:
   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]
   --without-PACKAGE       do not use PACKAGE (same as --with-PACKAGE=no)
-C compiler
   --with-gmp-includes     directory containing gmp.h
   --with-gmp-libraries    directory containing gmp library
   --with-gmp-framework-preferred
@@ -1461,52 +1471,6 @@
 
 } # ac_fn_c_try_compile
 
-# ac_fn_c_try_link LINENO
-# -----------------------
-# Try to link conftest.$ac_ext, and return whether this succeeded.
-ac_fn_c_try_link ()
-{
-  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  rm -f conftest.$ac_objext conftest$ac_exeext
-  if { { ac_try="$ac_link"
-case "(($ac_try" in
-  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
-  *) ac_try_echo=$ac_try;;
-esac
-eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
-  (eval "$ac_link") 2>conftest.err
-  ac_status=$?
-  if test -s conftest.err; then
-    grep -v '^ *+' conftest.err >conftest.er1
-    cat conftest.er1 >&5
-    mv -f conftest.er1 conftest.err
-  fi
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; } && {
-	 test -z "$ac_c_werror_flag" ||
-	 test ! -s conftest.err
-       } && test -s conftest$ac_exeext && {
-	 test "$cross_compiling" = yes ||
-	 test -x conftest$ac_exeext
-       }; then :
-  ac_retval=0
-else
-  $as_echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-	ac_retval=1
-fi
-  # Delete the IPA/IPO (Inter Procedural Analysis/Optimization) information
-  # created by the PGI compiler (conftest_ipa8_conftest.oo), as it would
-  # interfere with the next link command; also delete a directory that is
-  # left behind by Apple's compiler.  We do this before executing the actions.
-  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
-  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
-  as_fn_set_status $ac_retval
-
-} # ac_fn_c_try_link
-
 # ac_fn_c_try_cpp LINENO
 # ----------------------
 # Try to preprocess conftest.$ac_ext, and return whether this succeeded.
@@ -1708,6 +1672,52 @@
 
 } # ac_fn_c_check_header_compile
 
+# ac_fn_c_try_link LINENO
+# -----------------------
+# Try to link conftest.$ac_ext, and return whether this succeeded.
+ac_fn_c_try_link ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  rm -f conftest.$ac_objext conftest$ac_exeext
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>conftest.err
+  ac_status=$?
+  if test -s conftest.err; then
+    grep -v '^ *+' conftest.err >conftest.er1
+    cat conftest.er1 >&5
+    mv -f conftest.er1 conftest.err
+  fi
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 test -x conftest$ac_exeext
+       }; then :
+  ac_retval=0
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	ac_retval=1
+fi
+  # Delete the IPA/IPO (Inter Procedural Analysis/Optimization) information
+  # created by the PGI compiler (conftest_ipa8_conftest.oo), as it would
+  # interfere with the next link command; also delete a directory that is
+  # left behind by Apple's compiler.  We do this before executing the actions.
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_c_try_link
+
 # ac_fn_c_compute_int LINENO EXPR VAR INCLUDES
 # --------------------------------------------
 # Tries to find the compile-time value of EXPR in a program that includes
@@ -2243,7 +2253,6 @@
 
 
 
-
 # Safety check: Ensure that we are in the correct source directory.
 
 
@@ -2387,12 +2396,6 @@
     NONENONEs,x,x, &&
   program_prefix=${target_alias}-
 
-
-# Check whether --with-cc was given.
-if test "${with_cc+set}" = set; then :
-  withval=$with_cc; CC=$withval
-fi
-
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -3183,9 +3186,468 @@
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking how to run the C preprocessor" >&5
+$as_echo_n "checking how to run the C preprocessor... " >&6; }
+# On Suns, sometimes $CPP names a directory.
+if test -n "$CPP" && test -d "$CPP"; then
+  CPP=
+fi
+if test -z "$CPP"; then
+  if ${ac_cv_prog_CPP+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+      # Double quotes because CPP needs to be expanded
+    for CPP in "$CC -E" "$CC -E -traditional-cpp" "/lib/cpp"
+    do
+      ac_preproc_ok=false
+for ac_c_preproc_warn_flag in '' yes
+do
+  # Use a header file that comes with gcc, so configuring glibc
+  # with a fresh cross-compiler works.
+  # Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+  # <limits.h> exists even on freestanding compilers.
+  # On the NeXT, cc -E runs the code through the compiler's parser,
+  # not just through cpp. "Syntax error" is here to catch this case.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+		     Syntax error
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"; then :
 
+else
+  # Broken: fails on valid input.
+continue
+fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
+  # OK, works on sane cases.  Now check whether nonexistent headers
+  # can be detected and how.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <ac_nonexistent.h>
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"; then :
+  # Broken: success on invalid input.
+continue
+else
+  # Passes both tests.
+ac_preproc_ok=:
+break
+fi
+rm -f conftest.err conftest.i conftest.$ac_ext
 
+done
+# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
+rm -f conftest.i conftest.err conftest.$ac_ext
+if $ac_preproc_ok; then :
+  break
+fi
+
+    done
+    ac_cv_prog_CPP=$CPP
+
+fi
+  CPP=$ac_cv_prog_CPP
+else
+  ac_cv_prog_CPP=$CPP
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $CPP" >&5
+$as_echo "$CPP" >&6; }
+ac_preproc_ok=false
+for ac_c_preproc_warn_flag in '' yes
+do
+  # Use a header file that comes with gcc, so configuring glibc
+  # with a fresh cross-compiler works.
+  # Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+  # <limits.h> exists even on freestanding compilers.
+  # On the NeXT, cc -E runs the code through the compiler's parser,
+  # not just through cpp. "Syntax error" is here to catch this case.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+		     Syntax error
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"; then :
+
+else
+  # Broken: fails on valid input.
+continue
+fi
+rm -f conftest.err conftest.i conftest.$ac_ext
+
+  # OK, works on sane cases.  Now check whether nonexistent headers
+  # can be detected and how.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <ac_nonexistent.h>
+_ACEOF
+if ac_fn_c_try_cpp "$LINENO"; then :
+  # Broken: success on invalid input.
+continue
+else
+  # Passes both tests.
+ac_preproc_ok=:
+break
+fi
+rm -f conftest.err conftest.i conftest.$ac_ext
+
+done
+# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
+rm -f conftest.i conftest.err conftest.$ac_ext
+if $ac_preproc_ok; then :
+
+else
+  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "C preprocessor \"$CPP\" fails sanity check
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for grep that handles long lines and -e" >&5
+$as_echo_n "checking for grep that handles long lines and -e... " >&6; }
+if ${ac_cv_path_GREP+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -z "$GREP"; then
+  ac_path_GREP_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in grep ggrep; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_GREP" || continue
+# Check for GNU ac_path_GREP and select it if it is found.
+  # Check for GNU $ac_path_GREP
+case `"$ac_path_GREP" --version 2>&1` in
+*GNU*)
+  ac_cv_path_GREP="$ac_path_GREP" ac_path_GREP_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo 'GREP' >> "conftest.nl"
+    "$ac_path_GREP" -e 'GREP$' -e '-(cannot match)-' < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_GREP_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_GREP="$ac_path_GREP"
+      ac_path_GREP_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_GREP_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_GREP"; then
+    as_fn_error $? "no acceptable grep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
+  fi
+else
+  ac_cv_path_GREP=$GREP
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_GREP" >&5
+$as_echo "$ac_cv_path_GREP" >&6; }
+ GREP="$ac_cv_path_GREP"
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for egrep" >&5
+$as_echo_n "checking for egrep... " >&6; }
+if ${ac_cv_path_EGREP+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if echo a | $GREP -E '(a|b)' >/dev/null 2>&1
+   then ac_cv_path_EGREP="$GREP -E"
+   else
+     if test -z "$EGREP"; then
+  ac_path_EGREP_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in egrep; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_EGREP" || continue
+# Check for GNU ac_path_EGREP and select it if it is found.
+  # Check for GNU $ac_path_EGREP
+case `"$ac_path_EGREP" --version 2>&1` in
+*GNU*)
+  ac_cv_path_EGREP="$ac_path_EGREP" ac_path_EGREP_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo 'EGREP' >> "conftest.nl"
+    "$ac_path_EGREP" 'EGREP$' < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_EGREP_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_EGREP="$ac_path_EGREP"
+      ac_path_EGREP_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_EGREP_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_EGREP"; then
+    as_fn_error $? "no acceptable egrep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
+  fi
+else
+  ac_cv_path_EGREP=$EGREP
+fi
+
+   fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_EGREP" >&5
+$as_echo "$ac_cv_path_EGREP" >&6; }
+ EGREP="$ac_cv_path_EGREP"
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
+$as_echo_n "checking for ANSI C header files... " >&6; }
+if ${ac_cv_header_stdc+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <float.h>
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_header_stdc=yes
+else
+  ac_cv_header_stdc=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+if test $ac_cv_header_stdc = yes; then
+  # SunOS 4.x string.h does not declare mem*, contrary to ANSI.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <string.h>
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "memchr" >/dev/null 2>&1; then :
+
+else
+  ac_cv_header_stdc=no
+fi
+rm -f conftest*
+
+fi
+
+if test $ac_cv_header_stdc = yes; then
+  # ISC 2.0.2 stdlib.h does not declare free, contrary to ANSI.
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdlib.h>
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "free" >/dev/null 2>&1; then :
+
+else
+  ac_cv_header_stdc=no
+fi
+rm -f conftest*
+
+fi
+
+if test $ac_cv_header_stdc = yes; then
+  # /bin/cc in Irix-4.0.5 gets non-ANSI ctype macros unless using -ansi.
+  if test "$cross_compiling" = yes; then :
+  :
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <ctype.h>
+#include <stdlib.h>
+#if ((' ' & 0x0FF) == 0x020)
+# define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
+# define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
+#else
+# define ISLOWER(c) \
+		   (('a' <= (c) && (c) <= 'i') \
+		     || ('j' <= (c) && (c) <= 'r') \
+		     || ('s' <= (c) && (c) <= 'z'))
+# define TOUPPER(c) (ISLOWER(c) ? ((c) | 0x40) : (c))
+#endif
+
+#define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
+int
+main ()
+{
+  int i;
+  for (i = 0; i < 256; i++)
+    if (XOR (islower (i), ISLOWER (i))
+	|| toupper (i) != TOUPPER (i))
+      return 2;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+
+else
+  ac_cv_header_stdc=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_header_stdc" >&5
+$as_echo "$ac_cv_header_stdc" >&6; }
+if test $ac_cv_header_stdc = yes; then
+
+$as_echo "#define STDC_HEADERS 1" >>confdefs.h
+
+fi
+
+# On IRIX 5.3, sys/types and inttypes.h are conflicting.
+for ac_header in sys/types.h sys/stat.h stdlib.h string.h memory.h strings.h \
+		  inttypes.h stdint.h unistd.h
+do :
+  as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
+ac_fn_c_check_header_compile "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default
+"
+if eval test \"x\$"$as_ac_Header"\" = x"yes"; then :
+  cat >>confdefs.h <<_ACEOF
+#define `$as_echo "HAVE_$ac_header" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+
+done
+
+
+
+  ac_fn_c_check_header_mongrel "$LINENO" "minix/config.h" "ac_cv_header_minix_config_h" "$ac_includes_default"
+if test "x$ac_cv_header_minix_config_h" = xyes; then :
+  MINIX=yes
+else
+  MINIX=
+fi
+
+
+  if test "$MINIX" = yes; then
+
+$as_echo "#define _POSIX_SOURCE 1" >>confdefs.h
+
+
+$as_echo "#define _POSIX_1_SOURCE 2" >>confdefs.h
+
+
+$as_echo "#define _MINIX 1" >>confdefs.h
+
+  fi
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether it is safe to define __EXTENSIONS__" >&5
+$as_echo_n "checking whether it is safe to define __EXTENSIONS__... " >&6; }
+if ${ac_cv_safe_to_define___extensions__+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#         define __EXTENSIONS__ 1
+          $ac_includes_default
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ac_cv_safe_to_define___extensions__=yes
+else
+  ac_cv_safe_to_define___extensions__=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_safe_to_define___extensions__" >&5
+$as_echo "$ac_cv_safe_to_define___extensions__" >&6; }
+  test $ac_cv_safe_to_define___extensions__ = yes &&
+    $as_echo "#define __EXTENSIONS__ 1" >>confdefs.h
+
+  $as_echo "#define _ALL_SOURCE 1" >>confdefs.h
+
+  $as_echo "#define _GNU_SOURCE 1" >>confdefs.h
+
+  $as_echo "#define _POSIX_PTHREAD_SEMANTICS 1" >>confdefs.h
+
+  $as_echo "#define _TANDEM_SOURCE 1" >>confdefs.h
+
+
+
+
+
+
 # Check whether --with-gmp-includes was given.
 if test "${with_gmp_includes+set}" = set; then :
   withval=$with_gmp_includes; GMP_INCLUDE_DIRS=$withval; CPPFLAGS="-I$withval"
@@ -3233,7 +3695,6 @@
     if test "$GMP_PREFER_FRAMEWORK" = "YES"
     then
 
-
     if test "$HaveLibGmp" = "NO"
     then
         case $target_os in
@@ -3588,404 +4049,7 @@
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
     UseIntreeGmp=0
-    ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking how to run the C preprocessor" >&5
-$as_echo_n "checking how to run the C preprocessor... " >&6; }
-# On Suns, sometimes $CPP names a directory.
-if test -n "$CPP" && test -d "$CPP"; then
-  CPP=
-fi
-if test -z "$CPP"; then
-  if ${ac_cv_prog_CPP+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-      # Double quotes because CPP needs to be expanded
-    for CPP in "$CC -E" "$CC -E -traditional-cpp" "/lib/cpp"
-    do
-      ac_preproc_ok=false
-for ac_c_preproc_warn_flag in '' yes
-do
-  # Use a header file that comes with gcc, so configuring glibc
-  # with a fresh cross-compiler works.
-  # Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
-  # <limits.h> exists even on freestanding compilers.
-  # On the NeXT, cc -E runs the code through the compiler's parser,
-  # not just through cpp. "Syntax error" is here to catch this case.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#ifdef __STDC__
-# include <limits.h>
-#else
-# include <assert.h>
-#endif
-		     Syntax error
-_ACEOF
-if ac_fn_c_try_cpp "$LINENO"; then :
-
-else
-  # Broken: fails on valid input.
-continue
-fi
-rm -f conftest.err conftest.i conftest.$ac_ext
-
-  # OK, works on sane cases.  Now check whether nonexistent headers
-  # can be detected and how.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <ac_nonexistent.h>
-_ACEOF
-if ac_fn_c_try_cpp "$LINENO"; then :
-  # Broken: success on invalid input.
-continue
-else
-  # Passes both tests.
-ac_preproc_ok=:
-break
-fi
-rm -f conftest.err conftest.i conftest.$ac_ext
-
-done
-# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
-rm -f conftest.i conftest.err conftest.$ac_ext
-if $ac_preproc_ok; then :
-  break
-fi
-
-    done
-    ac_cv_prog_CPP=$CPP
-
-fi
-  CPP=$ac_cv_prog_CPP
-else
-  ac_cv_prog_CPP=$CPP
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $CPP" >&5
-$as_echo "$CPP" >&6; }
-ac_preproc_ok=false
-for ac_c_preproc_warn_flag in '' yes
-do
-  # Use a header file that comes with gcc, so configuring glibc
-  # with a fresh cross-compiler works.
-  # Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
-  # <limits.h> exists even on freestanding compilers.
-  # On the NeXT, cc -E runs the code through the compiler's parser,
-  # not just through cpp. "Syntax error" is here to catch this case.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#ifdef __STDC__
-# include <limits.h>
-#else
-# include <assert.h>
-#endif
-		     Syntax error
-_ACEOF
-if ac_fn_c_try_cpp "$LINENO"; then :
-
-else
-  # Broken: fails on valid input.
-continue
-fi
-rm -f conftest.err conftest.i conftest.$ac_ext
-
-  # OK, works on sane cases.  Now check whether nonexistent headers
-  # can be detected and how.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <ac_nonexistent.h>
-_ACEOF
-if ac_fn_c_try_cpp "$LINENO"; then :
-  # Broken: success on invalid input.
-continue
-else
-  # Passes both tests.
-ac_preproc_ok=:
-break
-fi
-rm -f conftest.err conftest.i conftest.$ac_ext
-
-done
-# Because of `break', _AC_PREPROC_IFELSE's cleaning code was skipped.
-rm -f conftest.i conftest.err conftest.$ac_ext
-if $ac_preproc_ok; then :
-
-else
-  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
-$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "C preprocessor \"$CPP\" fails sanity check
-See \`config.log' for more details" "$LINENO" 5; }
-fi
-
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for grep that handles long lines and -e" >&5
-$as_echo_n "checking for grep that handles long lines and -e... " >&6; }
-if ${ac_cv_path_GREP+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -z "$GREP"; then
-  ac_path_GREP_found=false
-  # Loop through the user's path and test for each of PROGNAME-LIST
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_prog in grep ggrep; do
-    for ac_exec_ext in '' $ac_executable_extensions; do
-      ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
-      as_fn_executable_p "$ac_path_GREP" || continue
-# Check for GNU ac_path_GREP and select it if it is found.
-  # Check for GNU $ac_path_GREP
-case `"$ac_path_GREP" --version 2>&1` in
-*GNU*)
-  ac_cv_path_GREP="$ac_path_GREP" ac_path_GREP_found=:;;
-*)
-  ac_count=0
-  $as_echo_n 0123456789 >"conftest.in"
-  while :
-  do
-    cat "conftest.in" "conftest.in" >"conftest.tmp"
-    mv "conftest.tmp" "conftest.in"
-    cp "conftest.in" "conftest.nl"
-    $as_echo 'GREP' >> "conftest.nl"
-    "$ac_path_GREP" -e 'GREP$' -e '-(cannot match)-' < "conftest.nl" >"conftest.out" 2>/dev/null || break
-    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
-    as_fn_arith $ac_count + 1 && ac_count=$as_val
-    if test $ac_count -gt ${ac_path_GREP_max-0}; then
-      # Best one so far, save it but keep looking for a better one
-      ac_cv_path_GREP="$ac_path_GREP"
-      ac_path_GREP_max=$ac_count
-    fi
-    # 10*(2^10) chars as input seems more than enough
-    test $ac_count -gt 10 && break
-  done
-  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
-esac
-
-      $ac_path_GREP_found && break 3
-    done
-  done
-  done
-IFS=$as_save_IFS
-  if test -z "$ac_cv_path_GREP"; then
-    as_fn_error $? "no acceptable grep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
-  fi
-else
-  ac_cv_path_GREP=$GREP
-fi
-
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_GREP" >&5
-$as_echo "$ac_cv_path_GREP" >&6; }
- GREP="$ac_cv_path_GREP"
-
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for egrep" >&5
-$as_echo_n "checking for egrep... " >&6; }
-if ${ac_cv_path_EGREP+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if echo a | $GREP -E '(a|b)' >/dev/null 2>&1
-   then ac_cv_path_EGREP="$GREP -E"
-   else
-     if test -z "$EGREP"; then
-  ac_path_EGREP_found=false
-  # Loop through the user's path and test for each of PROGNAME-LIST
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_prog in egrep; do
-    for ac_exec_ext in '' $ac_executable_extensions; do
-      ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
-      as_fn_executable_p "$ac_path_EGREP" || continue
-# Check for GNU ac_path_EGREP and select it if it is found.
-  # Check for GNU $ac_path_EGREP
-case `"$ac_path_EGREP" --version 2>&1` in
-*GNU*)
-  ac_cv_path_EGREP="$ac_path_EGREP" ac_path_EGREP_found=:;;
-*)
-  ac_count=0
-  $as_echo_n 0123456789 >"conftest.in"
-  while :
-  do
-    cat "conftest.in" "conftest.in" >"conftest.tmp"
-    mv "conftest.tmp" "conftest.in"
-    cp "conftest.in" "conftest.nl"
-    $as_echo 'EGREP' >> "conftest.nl"
-    "$ac_path_EGREP" 'EGREP$' < "conftest.nl" >"conftest.out" 2>/dev/null || break
-    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
-    as_fn_arith $ac_count + 1 && ac_count=$as_val
-    if test $ac_count -gt ${ac_path_EGREP_max-0}; then
-      # Best one so far, save it but keep looking for a better one
-      ac_cv_path_EGREP="$ac_path_EGREP"
-      ac_path_EGREP_max=$ac_count
-    fi
-    # 10*(2^10) chars as input seems more than enough
-    test $ac_count -gt 10 && break
-  done
-  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
-esac
-
-      $ac_path_EGREP_found && break 3
-    done
-  done
-  done
-IFS=$as_save_IFS
-  if test -z "$ac_cv_path_EGREP"; then
-    as_fn_error $? "no acceptable egrep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" "$LINENO" 5
-  fi
-else
-  ac_cv_path_EGREP=$EGREP
-fi
-
-   fi
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_EGREP" >&5
-$as_echo "$ac_cv_path_EGREP" >&6; }
- EGREP="$ac_cv_path_EGREP"
-
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
-$as_echo_n "checking for ANSI C header files... " >&6; }
-if ${ac_cv_header_stdc+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-#include <stdarg.h>
-#include <string.h>
-#include <float.h>
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_header_stdc=yes
-else
-  ac_cv_header_stdc=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-
-if test $ac_cv_header_stdc = yes; then
-  # SunOS 4.x string.h does not declare mem*, contrary to ANSI.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <string.h>
-
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "memchr" >/dev/null 2>&1; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f conftest*
-
-fi
-
-if test $ac_cv_header_stdc = yes; then
-  # ISC 2.0.2 stdlib.h does not declare free, contrary to ANSI.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "free" >/dev/null 2>&1; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f conftest*
-
-fi
-
-if test $ac_cv_header_stdc = yes; then
-  # /bin/cc in Irix-4.0.5 gets non-ANSI ctype macros unless using -ansi.
-  if test "$cross_compiling" = yes; then :
-  :
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <ctype.h>
-#include <stdlib.h>
-#if ((' ' & 0x0FF) == 0x020)
-# define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
-# define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
-#else
-# define ISLOWER(c) \
-		   (('a' <= (c) && (c) <= 'i') \
-		     || ('j' <= (c) && (c) <= 'r') \
-		     || ('s' <= (c) && (c) <= 'z'))
-# define TOUPPER(c) (ISLOWER(c) ? ((c) | 0x40) : (c))
-#endif
-
-#define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
-int
-main ()
-{
-  int i;
-  for (i = 0; i < 256; i++)
-    if (XOR (islower (i), ISLOWER (i))
-	|| toupper (i) != TOUPPER (i))
-      return 2;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-fi
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_header_stdc" >&5
-$as_echo "$ac_cv_header_stdc" >&6; }
-if test $ac_cv_header_stdc = yes; then
-
-$as_echo "#define STDC_HEADERS 1" >>confdefs.h
-
-fi
-
-# On IRIX 5.3, sys/types and inttypes.h are conflicting.
-for ac_header in sys/types.h sys/stat.h stdlib.h string.h memory.h strings.h \
-		  inttypes.h stdint.h unistd.h
-do :
-  as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
-ac_fn_c_check_header_compile "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default
-"
-if eval test \"x\$"$as_ac_Header"\" = x"yes"; then :
-  cat >>confdefs.h <<_ACEOF
-#define `$as_echo "HAVE_$ac_header" | $as_tr_cpp` 1
-_ACEOF
-
-fi
-
-done
-
-
-ac_fn_c_check_header_mongrel "$LINENO" "gmp.h" "ac_cv_header_gmp_h" "$ac_includes_default"
+    ac_fn_c_check_header_mongrel "$LINENO" "gmp.h" "ac_cv_header_gmp_h" "$ac_includes_default"
 if test "x$ac_cv_header_gmp_h" = xyes; then :
 
 else
diff --git a/configure.ac b/configure.ac
--- a/configure.ac
+++ b/configure.ac
@@ -1,15 +1,14 @@
+AC_PREREQ(2.60)
 AC_INIT([Haskell integer (GMP)], [1.0], [libraries@haskell.org], [integer])
-AC_PREREQ(2.52)
 
 # Safety check: Ensure that we are in the correct source directory.
 AC_CONFIG_SRCDIR([cbits/wrappers.c])
 
 AC_CANONICAL_TARGET
 
-AC_ARG_WITH([cc],
-            [C compiler],
-            [CC=$withval])
-AC_PROG_CC()
+AC_PROG_CC
+dnl make extensions visible to allow feature-tests to detect them lateron
+AC_USE_SYSTEM_EXTENSIONS
 
 
 dnl--------------------------------------------------------------------
diff --git a/integer-gmp.cabal b/integer-gmp.cabal
--- a/integer-gmp.cabal
+++ b/integer-gmp.cabal
@@ -1,5 +1,5 @@
 name:                integer-gmp
-version:             1.0.0.0
+version:             1.0.0.1
 synopsis:            Integer library based on GMP
 license:             BSD3
 license-file:        LICENSE
@@ -48,7 +48,7 @@
     UnliftedFFITypes
   build-depends:       ghc-prim
   hs-source-dirs:      src/
-  ghc-options: -this-package-key integer-gmp -Wall
+  ghc-options: -this-unit-id integer-gmp -Wall
   cc-options: -std=c99 -Wall
 
   include-dirs: include
diff --git a/src/GHC/Integer/Type.hs b/src/GHC/Integer/Type.hs
--- a/src/GHC/Integer/Type.hs
+++ b/src/GHC/Integer/Type.hs
@@ -426,7 +426,7 @@
 
 -- | Multiply two 'Integer's
 timesInteger :: Integer -> Integer -> Integer
-timesInteger _       (S# 0#) = S# 0#
+timesInteger !_      (S# 0#) = S# 0#
 timesInteger (S# 0#) _       = S# 0#
 timesInteger x       (S# 1#) = x
 timesInteger (S# 1#) y       = y
@@ -460,23 +460,23 @@
 
 -- | Construct 'Integer' from the product of two 'Int#'s
 timesInt2Integer :: Int# -> Int# -> Integer
-timesInt2Integer x# y# = case (# x# >=# 0#, y# >=# 0# #) of
-    (# 0#, 0# #) -> case timesWord2# (int2Word# (negateInt# x#))
+timesInt2Integer x# y# = case (# isTrue# (x# >=# 0#), isTrue# (y# >=# 0#) #) of
+    (# False, False #) -> case timesWord2# (int2Word# (negateInt# x#))
                                      (int2Word# (negateInt# y#)) of
         (# 0##,l #) -> inline wordToInteger l
         (# h  ,l #) -> Jp# (wordToBigNat2 h l)
 
-    (#  _, 0# #) -> case timesWord2# (int2Word# x#)
+    (#  True, False #) -> case timesWord2# (int2Word# x#)
                                      (int2Word# (negateInt# y#)) of
         (# 0##,l #) -> wordToNegInteger l
         (# h  ,l #) -> Jn# (wordToBigNat2 h l)
 
-    (# 0#,  _ #) -> case timesWord2# (int2Word# (negateInt# x#))
+    (# False,  True #) -> case timesWord2# (int2Word# (negateInt# x#))
                                      (int2Word# y#) of
         (# 0##,l #) -> wordToNegInteger l
         (# h  ,l #) -> Jn# (wordToBigNat2 h l)
 
-    (#  _,  _ #) -> case timesWord2# (int2Word# x#)
+    (#  True,  True #) -> case timesWord2# (int2Word# x#)
                                      (int2Word# y#) of
         (# 0##,l #) -> inline wordToInteger l
         (# h  ,l #) -> Jp# (wordToBigNat2 h l)
@@ -515,7 +515,7 @@
 
 -- | Test if /n/-th bit is set.
 testBitInteger :: Integer -> Int# -> Bool
-testBitInteger _  n# | isTrue# (n# <# 0#) = False
+testBitInteger !_  n# | isTrue# (n# <# 0#) = False
 testBitInteger (S# i#) n#
   | isTrue# (n# <# GMP_LIMB_BITS#) = isTrue# (((uncheckedIShiftL# 1# n#)
                                                `andI#` i#) /=# 0#)
@@ -614,7 +614,7 @@
 -- | Bitwise AND operation
 andInteger :: Integer -> Integer -> Integer
 -- short-cuts
-andInteger (S# 0#)       _       = S# 0#
+andInteger (S# 0#)     !_        = S# 0#
 andInteger _           (S# 0#)   = S# 0#
 andInteger (S# -1#)   y          = y
 andInteger x           (S# -1#)  = x
@@ -646,7 +646,7 @@
 quotRemInteger :: Integer -> Integer -> (# Integer, Integer #)
 quotRemInteger n       (S# 1#) = (# n, S# 0# #)
 quotRemInteger n      (S# -1#) = let !q = negateInteger n in (# q, (S# 0#) #)
-quotRemInteger _       (S# 0#) = (# S# (quotInt# 0# 0#),S# (remInt# 0# 0#) #)
+quotRemInteger !_      (S# 0#) = (# S# (quotInt# 0# 0#),S# (remInt# 0# 0#) #)
 quotRemInteger (S# 0#) _       = (# S# 0#, S# 0# #)
 quotRemInteger (S# n#) (S# d#) = case quotRemInt# n# d# of
     (# q#, r# #) -> (# S# q#, S# r# #)
@@ -679,7 +679,7 @@
 quotInteger :: Integer -> Integer -> Integer
 quotInteger n       (S# 1#) = n
 quotInteger n      (S# -1#) = negateInteger n
-quotInteger _       (S# 0#) = S# (quotInt# 0# 0#)
+quotInteger !_      (S# 0#) = S# (quotInt# 0# 0#)
 quotInteger (S# 0#) _       = S# 0#
 quotInteger (S# n#)  (S# d#) = S# (quotInt# n# d#)
 quotInteger (Jp# n)   (S# d#)
@@ -699,7 +699,7 @@
 {-# CONSTANT_FOLDED quotInteger #-}
 
 remInteger :: Integer -> Integer -> Integer
-remInteger _        (S# 1#) = S# 0#
+remInteger !_       (S# 1#) = S# 0#
 remInteger _       (S# -1#) = S# 0#
 remInteger _        (S# 0#) = S# (remInt# 0# 0#)
 remInteger (S# 0#) _        = S# 0#
@@ -763,7 +763,7 @@
 
 -- | Compute least common multiple.
 lcmInteger :: Integer -> Integer -> Integer
-lcmInteger (S# 0#) _   = S# 0#
+lcmInteger (S# 0#) !_  = S# 0#
 lcmInteger (S# 1#)  b  = absInteger b
 lcmInteger (S# -1#) b  = absInteger b
 lcmInteger _ (S# 0#)   = S# 0#
@@ -835,7 +835,7 @@
 
 eqBigNatWord# :: BigNat -> GmpLimb# -> Int#
 eqBigNatWord# bn w#
-    = sizeofBigNat# bn ==# 1# `andI#` (bigNatToWord bn `eqWord#` w#)
+    = (sizeofBigNat# bn ==# 1#) `andI#` (bigNatToWord bn `eqWord#` w#)
 
 
 -- | Same as @'indexBigNat#' bn 0\#@
@@ -998,7 +998,7 @@
 sqrBigNat x = timesBigNat x x -- TODO: mpn_sqr
 
 timesBigNatWord :: BigNat -> GmpLimb# -> BigNat
-timesBigNatWord _ 0## = zeroBigNat
+timesBigNatWord !_ 0## = zeroBigNat
 timesBigNatWord x 1## = x
 timesBigNatWord x@(BN# x#) y#
   | isTrue# (nx# ==# 1#) =
@@ -1014,8 +1014,25 @@
   where
     nx# = sizeofBigNat# x
 
+-- | Specialised version of
+--
+-- > bitBigNat = shiftLBigNat (wordToBigNat 1##)
+--
+-- avoiding a few redundant allocations
 bitBigNat :: Int# -> BigNat
-bitBigNat i# = shiftLBigNat (wordToBigNat 1##) i# -- FIXME
+bitBigNat i#
+  | isTrue# (i#  <#  0#) = zeroBigNat -- or maybe 'nullBigNat'?
+  | isTrue# (i# ==#  0#) = oneBigNat
+  | True = runS $ do
+      mbn@(MBN# mba#) <- newBigNat# (li# +# 1#)
+      -- FIXME: do we really need to zero-init MBAs returned by 'newByteArray#'?
+      -- clear all limbs (except for the most-significant limb)
+      _ <- svoid (setByteArray# mba# 0# (li# `uncheckedIShiftL#` GMP_LIMB_SHIFT#) 0#)
+      -- set single bit in most-significant limb
+      _ <- svoid (writeBigNat# mbn li# (uncheckedShiftL# 1## bi#))
+      unsafeFreezeBigNat# mbn
+  where
+    (# li#, bi# #) = quotRemInt# i# GMP_LIMB_BITS#
 
 testBitBigNat :: BigNat -> Int# -> Bool
 testBitBigNat bn i#
@@ -1104,9 +1121,9 @@
     ior' a# na# b# nb# = do -- na >= nb
         mbn@(MBN# mba#) <- newBigNat# na#
         _ <- liftIO (c_mpn_ior_n mba# a# b# nb#)
-        _ <- case na# ==# nb# of
-            0# -> svoid (copyWordArray# a# nb# mba# nb# (na# -# nb#))
-            _  -> return ()
+        _ <- case isTrue# (na# ==# nb#) of
+            False -> svoid (copyWordArray# a# nb# mba# nb# (na# -# nb#))
+            True  -> return ()
         unsafeFreezeBigNat# mbn
 
     nx# = sizeofBigNat# x
@@ -1123,10 +1140,10 @@
     xor' a# na# b# nb# = do -- na >= nb
         mbn@(MBN# mba#) <- newBigNat# na#
         _ <- liftIO (c_mpn_xor_n mba# a# b# nb#)
-        case na# ==# nb# of
-            0# -> do _ <- svoid (copyWordArray# a# nb# mba# nb# (na# -# nb#))
-                     unsafeFreezeBigNat# mbn
-            _  -> unsafeRenormFreezeBigNat# mbn
+        case isTrue# (na# ==# nb#) of
+            False -> do _ <- svoid (copyWordArray# a# nb# mba# nb# (na# -# nb#))
+                        unsafeFreezeBigNat# mbn
+            True  -> unsafeRenormFreezeBigNat# mbn
 
     nx# = sizeofBigNat# x
     ny# = sizeofBigNat# y
@@ -1139,9 +1156,9 @@
   | True = runS $ do
       mbn@(MBN# mba#) <- newBigNat# nx#
       _ <- liftIO (c_mpn_andn_n mba# x# y# n#)
-      _ <- case nx# ==# n# of
-            0# -> svoid (copyWordArray# x# n# mba# n# (nx# -# n#))
-            _  -> return ()
+      _ <- case isTrue# (nx# ==# n#) of
+            False -> svoid (copyWordArray# x# n# mba# n# (nx# -# n#))
+            True  -> return ()
       unsafeRenormFreezeBigNat# mbn
   where
     n# | isTrue# (nx# <# ny#) = nx#
@@ -1214,7 +1231,7 @@
 
 -- | Note: Result of div/0 undefined
 quotRemBigNatWord :: BigNat -> GmpLimb# -> (# BigNat, GmpLimb# #)
-quotRemBigNatWord _            0## = (# nullBigNat, 0## #)
+quotRemBigNatWord !_           0## = (# nullBigNat, 0## #)
 quotRemBigNatWord n            1## = (# n,          0## #)
 quotRemBigNatWord n@(BN# nba#) d# = case compareBigNatWord n d# of
     LT -> (# zeroBigNat, bigNatToWord n #)
@@ -1249,9 +1266,9 @@
         mbn@(MBN# mba#) <- newBigNat# nb#
         I# rn'# <- liftIO (c_mpn_gcd# mba# a# na# b# nb#)
         let rn# = narrowGmpSize# rn'#
-        case rn# ==# nb# of
-            0# -> unsafeShrinkFreezeBigNat# mbn rn#
-            _  -> unsafeFreezeBigNat# mbn
+        case isTrue# (rn# ==# nb#) of
+            False -> unsafeShrinkFreezeBigNat# mbn rn#
+            True  -> unsafeFreezeBigNat# mbn
 
     nx# = sizeofBigNat# x
     ny# = sizeofBigNat# y
@@ -1284,9 +1301,9 @@
             sn#  = absI# ssn#
         s' <- unsafeShrinkFreezeBigNat# s sn#
         g' <- unsafeRenormFreezeBigNat# g
-        case ssn# >=# 0# of
-            0# -> return ( g', NegBN s' )
-            _  -> return ( g', PosBN s' )
+        case isTrue# (ssn# >=# 0#) of
+            False -> return ( g', NegBN s' )
+            True  -> return ( g', PosBN s' )
 
     !(BN# x#) = absSBigNat x
     !(BN# y#) = absSBigNat y
@@ -1351,9 +1368,9 @@
     r@(MBN# r#) <- newBigNat# mn#
     I# rn_# <- liftIO (integer_gmp_powm# r# b# bn# e# en# m# mn#)
     let rn# = narrowGmpSize# rn_#
-    case rn# ==# mn# of
-        0# -> unsafeShrinkFreezeBigNat# r rn#
-        _  -> unsafeFreezeBigNat# r
+    case isTrue# (rn# ==# mn#) of
+        False -> unsafeShrinkFreezeBigNat# r rn#
+        True  -> unsafeFreezeBigNat# r
   where
     !(BN# b#) = absSBigNat b
     !(BN# e#) = absSBigNat e
@@ -1413,9 +1430,9 @@
     r@(MBN# r#) <- newBigNat# mn#
     I# rn_# <- liftIO (integer_gmp_invert# r# x# xn# m# mn#)
     let rn# = narrowGmpSize# rn_#
-    case rn# ==# mn# of
-        0# -> unsafeShrinkFreezeBigNat# r rn#
-        _  -> unsafeFreezeBigNat# r
+    case isTrue# (rn# ==# mn#) of
+        False -> unsafeShrinkFreezeBigNat# r rn#
+        True  -> unsafeFreezeBigNat# r
   where
     !(BN# x#) = absSBigNat x
     xn# = ssizeofSBigNat# x
@@ -1611,9 +1628,11 @@
 
 data MutBigNat s = MBN# !(MutableByteArray# s)
 
-sizeofMutBigNat# :: MutBigNat s -> GmpSize#
-sizeofMutBigNat# (MBN# x#)
-    = sizeofMutableByteArray# x# `uncheckedIShiftRL#` GMP_LIMB_SHIFT#
+getSizeofMutBigNat# :: MutBigNat s -> State# s -> (# State# s, GmpSize# #)
+--getSizeofMutBigNat# :: MutBigNat s -> S s GmpSize#
+getSizeofMutBigNat# (MBN# x#) s =
+    case getSizeofMutableByteArray# x# s of
+        (# s', n# #) -> (# s', n# `uncheckedIShiftRL#` GMP_LIMB_SHIFT# #)
 
 newBigNat# :: GmpSize# -> S s (MutBigNat s)
 newBigNat# limbs# s =
@@ -1634,40 +1653,42 @@
 
 resizeMutBigNat# :: MutBigNat s -> GmpSize# -> S s (MutBigNat s)
 resizeMutBigNat# (MBN# mba0#) nsz# s
-  | isTrue# (bsz# ==# sizeofMutableByteArray# mba0#) = (# s, MBN# mba0# #)
-  | True = case resizeMutableByteArray# mba0# bsz# s of
-        (# s', mba# #) -> (# s' , MBN# mba# #)
+  | isTrue# (bsz# ==# n#) = (# s', MBN# mba0# #)
+  | True =
+    case resizeMutableByteArray# mba0# bsz# s' of
+        (# s'', mba# #) -> (# s'', MBN# mba# #)
   where
     bsz# = nsz# `uncheckedIShiftL#` GMP_LIMB_SHIFT#
+    (# s', n# #) = getSizeofMutableByteArray# mba0# s
 
 shrinkMutBigNat# :: MutBigNat s -> GmpSize# -> State# s -> State# s
-shrinkMutBigNat# (MBN# mba0#) nsz#
-  | isTrue# (bsz# ==# sizeofMutableByteArray# mba0#) = \s -> s -- no-op
-  | True = shrinkMutableByteArray# mba0# bsz#
+shrinkMutBigNat# (MBN# mba0#) nsz# s
+  | isTrue# (bsz# ==# n#) = s' -- no-op
+  | True                  = shrinkMutableByteArray# mba0# bsz# s'
   where
     bsz# = nsz# `uncheckedIShiftL#` GMP_LIMB_SHIFT#
+    (# s', n# #) = getSizeofMutableByteArray# mba0# s
 
 unsafeSnocFreezeBigNat# :: MutBigNat s -> GmpLimb# -> S s BigNat
-unsafeSnocFreezeBigNat# mbn0@(MBN# mba0#) limb# = do
-    -- (MBN# mba#) <- newBigNat# (n# +# 1#)
-    -- _ <- svoid (copyMutableByteArray# mba0# 0# mba# 0# nb0#)
-    (MBN# mba#) <- resizeMutBigNat# mbn0 (n# +# 1#)
-    _ <- svoid (writeWordArray# mba# n# limb#)
-    unsafeFreezeBigNat# (MBN# mba#)
+unsafeSnocFreezeBigNat# mbn0@(MBN# mba0#) limb# s = go s'
   where
     n#   = nb0# `uncheckedIShiftRL#` GMP_LIMB_SHIFT#
-    nb0# = sizeofMutableByteArray# mba0#
+    (# s', nb0# #) = getSizeofMutableByteArray# mba0# s
+    go = do
+        (MBN# mba#) <- resizeMutBigNat# mbn0 (n# +# 1#)
+        _ <- svoid (writeWordArray# mba# n# limb#)
+        unsafeFreezeBigNat# (MBN# mba#)
 
 -- | May shrink underlyng 'ByteArray#' if needed to satisfy BigNat invariant
 unsafeRenormFreezeBigNat# :: MutBigNat s -> S s BigNat
 unsafeRenormFreezeBigNat# mbn s
-  | isTrue# (n0# ==# 0#)  = (# s', nullBigNat #)
-  | isTrue# (n#  ==# 0#)  = (# s', zeroBigNat #)
-  | isTrue# (n#  ==# n0#) = (unsafeFreezeBigNat# mbn) s'
-  | True                  = (unsafeShrinkFreezeBigNat# mbn n#) s'
+  | isTrue# (n0# ==# 0#)  = (# s'', nullBigNat #)
+  | isTrue# (n#  ==# 0#)  = (# s'', zeroBigNat #)
+  | isTrue# (n#  ==# n0#) = (unsafeFreezeBigNat# mbn) s''
+  | True                  = (unsafeShrinkFreezeBigNat# mbn n#) s''
   where
-    (# s', n# #) = normSizeofMutBigNat'# mbn n0# s
-    n0# = sizeofMutBigNat# mbn
+    (# s', n0# #) = getSizeofMutBigNat# mbn s
+    (# s'', n# #) = normSizeofMutBigNat'# mbn n0# s'
 
 -- | Shrink MBN
 unsafeShrinkFreezeBigNat# :: MutBigNat s -> GmpSize# -> S s BigNat
@@ -1695,9 +1716,10 @@
 
 -- | Version of 'normSizeofMutBigNat'#' which scans all allocated 'MutBigNat#'
 normSizeofMutBigNat# :: MutBigNat s -> State# s -> (# State# s, Int# #)
-normSizeofMutBigNat# mbn@(MBN# mba) = normSizeofMutBigNat'# mbn sz#
+normSizeofMutBigNat# mbn@(MBN# mba) s = normSizeofMutBigNat'# mbn sz# s'
   where
-    sz# = sizeofMutableByteArray# mba `uncheckedIShiftRA#` GMP_LIMB_SHIFT#
+    (# s', n# #) = getSizeofMutableByteArray# mba s
+    sz# = n# `uncheckedIShiftRA#` GMP_LIMB_SHIFT#
 
 -- | Find most-significant non-zero limb and return its index-position
 -- plus one. Start scanning downward from the initial limb-size
@@ -1726,10 +1748,12 @@
   | isTrue# (n#  ==# 0#)    = zeroBigNat
   | isTrue# (baszr# ==# 0#) -- i.e. ba# is multiple of limb-size
   , isTrue# (baszq# ==# n#) = (BN# ba#)
-  | True = runS $ do
-      mbn@(MBN# mba#) <- newBigNat# n#
-      _ <- svoid (copyByteArray# ba# 0# mba# 0# (sizeofMutableByteArray# mba#))
-      unsafeFreezeBigNat# mbn
+  | True = runS $ \s ->
+      let (# s', mbn@(MBN# mba#) #) = newBigNat# n# s
+          (# s'', ba_sz# #) = getSizeofMutableByteArray# mba# s'
+          go = do _ <- svoid (copyByteArray# ba# 0# mba# 0# ba_sz# )
+                  unsafeFreezeBigNat# mbn
+      in go s''
   where
     (# baszq#, baszr# #) = quotRemInt# (sizeofByteArray# ba#) GMP_LIMB_BYTES#
 
@@ -1850,9 +1874,9 @@
 isValidBigNat# (BN# ba#)
   = (szq# ># 0#) `andI#` (szr# ==# 0#) `andI#` isNorm#
   where
-    isNorm# = case szq# ># 1# of
-                1# -> (indexWordArray# ba# (szq# -# 1#)) `neWord#` 0##
-                _  -> 1#
+    isNorm#
+      | isTrue# (szq# ># 1#) = (indexWordArray# ba# (szq# -# 1#)) `neWord#` 0##
+      | True                 = 1#
 
     sz# = sizeofByteArray# ba#
 
@@ -1910,8 +1934,7 @@
 
 -- NB: equivalent of GHC.IO.unsafeDupablePerformIO, see notes there
 runS :: S RealWorld a -> a
-runS m = lazy (case m realWorld# of (# _, r #) -> r)
-{-# NOINLINE runS #-}
+runS m = case runRW# m of (# _, a #) -> a
 
 -- stupid hack
 fail :: [Char] -> S s a
@@ -1963,13 +1986,6 @@
   | isTrue# (x# `eqWord#` y#) = EQ
   | True                      = GT
 {-# INLINE cmpW# #-}
-
-subWordC# :: Word# -> Word# -> (# Word#, Int# #)
-subWordC# x# y# = (# d#, c# #)
-  where
-    d# = x# `minusWord#` y#
-    c# = d# `gtWord#` x#
-{-# INLINE subWordC# #-}
 
 bitWord# :: Int# -> Word#
 bitWord# = uncheckedShiftL# 1##