Index: autoconf/configure.ac
===================================================================
--- autoconf/configure.ac
+++ autoconf/configure.ac
@@ -97,6 +97,11 @@
 
 dnl Let ISL's configure generate isl_config.h and gitversion.h
 AC_CONFIG_SUBDIRS(lib/External/isl)
+AC_CONFIG_COMMANDS_POST([
+	dnl Configure ISL with small integer optimization, but do not add the
+	dnl ooption to config.status as it is mandatory for Polly.
+	ac_configure_args="$ac_configure_args --with-int=imath-32"
+])
 
 dnl This must be last
 AC_CONFIG_HEADERS(include/polly/Config/config.h)
Index: configure
===================================================================
--- configure
+++ configure
@@ -2499,6 +2499,7 @@
 subdirs="$subdirs lib/External/isl"
 
 
+
 ac_config_headers="$ac_config_headers include/polly/Config/config.h"
 
 cat >confcache <<\_ACEOF
@@ -3762,6 +3763,9 @@
   as_fn_error $? "write failure creating $CONFIG_STATUS" "$LINENO" 5
 
 
+			ac_configure_args="$ac_configure_args --with-int=imath-32"
+
+
 # configure is writing to config.log, and then calls config.status.
 # config.status does its own redirection, appending to config.log.
 # Unfortunately, on DOS this fails, as config.log is still kept open
Index: lib/CMakeLists.txt
===================================================================
--- lib/CMakeLists.txt
+++ lib/CMakeLists.txt
@@ -40,7 +40,7 @@
 # Enable small integer optimization and imath
 set(USE_GMP_FOR_MP OFF)
 set(USE_IMATH_FOR_MP ON)
-set(USE_SMALL_INT_OPT OFF)
+set(USE_SMALL_INT_OPT ON)
 
 # Determine compiler characteristics
 include(CheckCSourceCompiles)
@@ -112,6 +112,7 @@
     External/isl/isl_ilp.c
     External/isl/isl_imath.c
     External/isl/isl_input.c
+    External/isl/isl_int_sioimath.c
     External/isl/isl_local_space.c
     External/isl/isl_lp.c
     External/isl/isl_map.c
@@ -148,7 +149,7 @@
     External/isl/isl_transitive_closure.c
     External/isl/isl_union_map.c
     External/isl/isl_val.c
-    External/isl/isl_val_imath.c
+    External/isl/isl_val_sioimath.c
     External/isl/isl_vec.c
     External/isl/isl_version.c
     External/isl/isl_vertices.c
Index: lib/Makefile
===================================================================
--- lib/Makefile
+++ lib/Makefile
@@ -61,6 +61,7 @@
            External/isl/isl_ilp.c \
            External/isl/isl_imath.c \
            External/isl/isl_input.c \
+           External/isl/isl_int_sioimath.c \
            External/isl/isl_local_space.c \
            External/isl/isl_lp.c \
            External/isl/isl_map.c \
@@ -97,7 +98,7 @@
            External/isl/isl_transitive_closure.c \
            External/isl/isl_union_map.c \
            External/isl/isl_val.c \
-           External/isl/isl_val_imath.c \
+           External/isl/isl_val_sioimath.c \
            External/isl/isl_vec.c \
            External/isl/isl_version.c \
            External/isl/isl_vertices.c \