Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -434,6 +434,8 @@
 option(LLVM_USE_SPLIT_DWARF
   "Use -gsplit-dwarf when compiling llvm." OFF)
 
+option(LLVM_INCLUDE_ISL "Include the integer set library to the build" OFF)
+
 option(LLVM_POLLY_LINK_INTO_TOOLS "Statically link Polly into tools (if available)" ON)
 option(LLVM_POLLY_BUILD "Build LLVM with Polly" ON)
 
@@ -969,6 +971,22 @@
     PATTERN ".svn" EXCLUDE
     )
 
+  if (LLVM_INCLUDE_ISL)
+    install(DIRECTORY contrib/isl/include/isl
+      DESTINATION include/llvm/ISL
+      COMPONENT llvm-headers
+      FILES_MATCHING
+      PATTERN "*.h"
+      )
+
+    install(DIRECTORY ${LLVM_BINARY_DIR}/lib/ISL/isl/include/isl
+      DESTINATION include/llvm/ISL
+      COMPONENT llvm-headers
+      FILES_MATCHING
+      PATTERN "*.h"
+      )
+  endif ()
+
   # Installing the headers needs to depend on generating any public
   # tablegen'd headers.
   add_custom_target(llvm-headers DEPENDS intrinsics_gen)
Index: contrib/isl-merge.py
===================================================================
--- /dev/null
+++ contrib/isl-merge.py
@@ -0,0 +1,64 @@
+#! /usr/bin/env python3
+# -*- coding: UTF-8 -*-
+
+import os
+import subprocess
+
+def main():
+    # TODO: Does not yet update imath
+    print("Updating to latest isl version...")
+
+    # Get the version we already merged in
+    idfile = os.path.join('isl', 'GIT_HEAD_ID')
+    with open(idfile, 'rt') as f:
+        ca = f.readline().rstrip()
+    if not ca or ca.isspace():
+        raise Exception("Error reading GIT_HEAD_ID")
+
+    # Remember the LLVM trunk revision for later
+    llvmhead = subprocess.check_output(
+        ['git', 'rev-parse', 'HEAD'], universal_newlines=True).rstrip()
+
+    # Fetch the latest isl from the official repository
+    subprocess.check_call(
+        ['git', 'fetch', 'http://repo.or.cz/isl.git', 'master'])
+    isldesc = subprocess.check_output(
+        ['git', 'describe', 'FETCH_HEAD'], universal_newlines=True).rstrip()
+    if isldesc == ca:
+        print("Already at latest version, abort")
+        return
+
+    # Update GIT_HEAD_ID
+    with open(idfile, 'wt') as f:
+        f.write(isldesc)
+    subprocess.check_call(['git', 'add', idfile])
+    subprocess.check_call(['git', 'commit', '-m',
+        ("Update GIT_HEAD_ID\n"
+         "\n"
+         "This commit is only temporary to have an updated GIT_HEAD_ID\n"
+         "in the repository even if a merge conflict occurs")])
+
+    # Do the actual merge
+    # Cannot use 'git merge' because it expects the existence of a common
+    # ancestor commit. The linear history of LLVM does not allow subtree
+    # merge commits to find such an ancestor, hence we use 'git rebase --onto'
+    # which acts like a cherry-pick.
+    try:
+        subprocess.check_call(
+            ['git', 'rebase', '-Xsubtree=contrib/isl',
+             ca, 'FETCH_HEAD', '--onto', 'HEAD'])
+    except:
+        print("A merge conflict occurred, manual commit necessary")
+        return
+
+    print("Rebase succeeded, squash and commit...")
+    subprocess.check_call(['git', 'reset', '--soft', llvmhead])
+    subprocess.check_call(
+        ['git', 'commit', '-m', "Update isl to {desc}".format(desc=isldesc)])
+
+    print()
+    print("Done. Push using 'git svn dcommit'"
+          "(maybe verify using 'git svn dcommit -n' first)")
+
+if __name__ == '__main__':
+    main()
Index: contrib/isl/.gitmodules
===================================================================
--- contrib/isl/.gitmodules
+++ /dev/null
@@ -1,3 +0,0 @@
-[submodule "imath"]
-	path = imath
-	url = https://github.com/creachadair/imath.git
Index: contrib/isl/GIT_HEAD_ID
===================================================================
--- /dev/null
+++ contrib/isl/GIT_HEAD_ID
@@ -0,0 +1 @@
+isl-0.18-979-g130e0d9
\ No newline at end of file
Index: lib/CMakeLists.txt
===================================================================
--- lib/CMakeLists.txt
+++ lib/CMakeLists.txt
@@ -26,3 +26,6 @@
 add_subdirectory(XRay)
 add_subdirectory(Testing)
 add_subdirectory(WindowsManifest)
+if (LLVM_INCLUDE_ISL)
+  add_subdirectory(ISL)
+endif ()
\ No newline at end of file
Index: lib/ISL/CMakeLists.txt
===================================================================
--- /dev/null
+++ lib/ISL/CMakeLists.txt
@@ -0,0 +1,297 @@
+set(ISL_SOURCE_DIR "${LLVM_MAIN_SRC_DIR}/contrib/isl")
+set(ISL_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/isl")
+
+# Determine version of isl
+if (EXISTS "${ISL_SOURCE_DIR}/GIT_HEAD_ID")
+  # The source comes from a 'make dist' archive
+  file(READ "${ISL_SOURCE_DIR}/GIT_HEAD_ID" ISL_GIT_HEAD_ID)
+  string(STRIP "${ISL_GIT_HEAD_ID}" ISL_GIT_HEAD_ID)
+elseif (EXISTS "${ISL_SOURCE_DIR}/gitversion.h")
+  # The source directory is preconfigured
+  file(READ "${ISL_SOURCE_DIR}/gitversion.h" GITVERSION_H)
+  string(REGEX REPLACE ".*\\\"([^\\\"]*)\\\".*" "\\1" ISL_GIT_HEAD_ID "${GITVERSION_H}")
+elseif ()
+  # Unknown revision
+  set(ISL_GIT_HEAD_ID "UNKNOWN")
+endif ()
+
+message(STATUS "isl version: ${ISL_GIT_HEAD_ID}")
+
+# Enable small integer optimization and imath. We currently do not allow
+# configuring them.
+set(USE_GMP_FOR_MP OFF)
+set(USE_IMATH_FOR_MP ON)
+set(USE_SMALL_INT_OPT ON)
+
+# Determine compiler characteristics
+include(CheckCSourceCompiles)
+
+# Like check_c_source_compiles, but sets the result to either
+# 0 (error while compiling) or 1 (compiled successfully)
+# Required for compatibility with autotool's AC_CHECK_DECLS
+function (check_c_source_compiles_numeric _prog _var)
+  check_c_source_compiles("${_prog}" "${_var}")
+  if ("${${_var}}")
+    set("${_var}" 1 PARENT_SCOPE)
+  else ()
+    set("${_var}" 0 PARENT_SCOPE)
+  endif ()
+endfunction ()
+
+# Check for the existance of a type
+function (check_c_type_exists _type _files _variable)
+  set(_includes "")
+  foreach (file_name ${_files})
+    set(_includes "${_includes}#include<${file_name}>\n")
+  endforeach()
+  check_c_source_compiles("
+  ${_includes}
+  ${_type} typeVar;
+  int main() {
+  return 0;
+  }
+  " ${_variable})
+endfunction ()
+
+check_c_source_compiles("
+int func(void) __attribute__((__warn_unused_result__));
+int main() { return 0; }
+" HAS_ATTRIBUTE_WARN_UNUSED_RESULT)
+set(GCC_WARN_UNUSED_RESULT)
+if (HAS_ATTRIBUTE_WARN_UNUSED_RESULT)
+  set(GCC_WARN_UNUSED_RESULT "__attribute__((__warn_unused_result__))")
+endif ()
+
+check_c_source_compiles("
+__attribute__ ((unused)) static void foo(void);
+int main() { return 0; }
+" HAVE___ATTRIBUTE__)
+
+check_c_source_compiles_numeric("
+#include <strings.h>
+int main() { (void)ffs(0); return 0; }
+" HAVE_DECL_FFS)
+
+check_c_source_compiles_numeric("
+int main() { (void)__builtin_ffs(0); return 0; }
+" HAVE_DECL___BUILTIN_FFS)
+
+check_c_source_compiles_numeric("
+#include <intrin.h>
+int main() { (void)_BitScanForward(NULL, 0); return 0; }
+" HAVE_DECL__BITSCANFORWARD)
+
+if (NOT HAVE_DECL_FFS AND
+    NOT HAVE_DECL___BUILTIN_FFS AND
+    NOT HAVE_DECL__BITSCANFORWARD)
+  message(FATAL_ERROR "No ffs implementation found")
+endif ()
+
+check_c_source_compiles_numeric("
+#include <strings.h>
+int main() { (void)strcasecmp(\"\", \"\"); return 0; }
+" HAVE_DECL_STRCASECMP)
+
+check_c_source_compiles_numeric("
+#include <string.h>
+int main() { (void)_stricmp(\"\", \"\"); return 0; }
+" HAVE_DECL__STRICMP)
+
+if (NOT HAVE_DECL_STRCASECMP AND NOT HAVE_DECL__STRICMP)
+  message(FATAL_ERROR "No strcasecmp implementation found")
+endif ()
+
+check_c_source_compiles_numeric("
+#include <strings.h>
+int main() { (void)strncasecmp(\"\", \"\", 0); return 0; }
+" HAVE_DECL_STRNCASECMP)
+
+check_c_source_compiles_numeric("
+#include <string.h>
+int main() { (void)_strnicmp(\"\", \"\", 0); return 0; }
+" HAVE_DECL__STRNICMP)
+
+if (NOT HAVE_DECL_STRNCASECMP AND NOT HAVE_DECL__STRNICMP)
+  message(FATAL_ERROR "No strncasecmp implementation found")
+endif ()
+
+check_c_source_compiles_numeric("
+#include <stdio.h>
+int main() { snprintf((void*)0, 0, \" \"); return 0; }
+" HAVE_DECL_SNPRINTF)
+
+check_c_source_compiles_numeric("
+#include <stdio.h>
+int main() { _snprintf((void*)0, 0, \" \"); return 0; }
+" HAVE_DECL__SNPRINTF)
+
+if (NOT HAVE_DECL_SNPRINTF AND NOT HAVE_DECL__SNPRINTF)
+  message(FATAL_ERROR "No snprintf implementation found")
+endif ()
+
+check_c_type_exists(uint8_t "" HAVE_UINT8T)
+check_c_type_exists(uint8_t "stdint.h" HAVE_STDINT_H)
+check_c_type_exists(uint8_t "inttypes.h" HAVE_INTTYPES_H)
+check_c_type_exists(uint8_t "sys/types.h" HAVE_SYS_INTTYPES_H)
+if (HAVE_UINT8T)
+  set(INCLUDE_STDINT_H "")
+elseif (HAVE_STDINT_H)
+  set(INCLUDE_STDINT_H "stdint.h")
+elseif (HAVE_INTTYPES_H)
+  set(INCLUDE_STDINT_H "inttypes.h")
+elseif (HAVE_SYS_INTTYPES_H)
+  set(INCLUDE_STDINT_H "sys/inttypes.h")
+else ()
+  message(FATAL_ERROR "No stdint.h or compatible found")
+endif ()
+
+# Write probing result.
+configure_file("stdint.h.cmake" "${ISL_BINARY_DIR}/include/isl/stdint.h")
+configure_file("gitversion.h.cmake" "${ISL_BINARY_DIR}/gitversion.h")
+configure_file("isl_config.h.cmake" "${ISL_BINARY_DIR}/isl_config.h")
+configure_file("isl_srcdir.c.cmake" "${ISL_BINARY_DIR}/isl_srcdir.c")
+
+# isl files to compile.
+set (ISL_FILES
+  basis_reduction_tab.c
+  isl_aff.c
+  isl_affine_hull.c
+  isl_arg.c
+  isl_ast_build.c
+  isl_ast_build_expr.c
+  isl_ast.c
+  isl_ast_codegen.c
+  isl_ast_graft.c
+  isl_bernstein.c
+  isl_blk.c
+  isl_bound.c
+  isl_coalesce.c
+  isl_constraint.c
+  isl_convex_hull.c
+  isl_ctx.c
+  isl_deprecated.c
+  isl_dim_map.c
+  isl_equalities.c
+  isl_factorization.c
+  isl_farkas.c
+  isl_ffs.c
+  isl_flow.c
+  isl_fold.c
+  isl_hash.c
+  isl_id.c
+  isl_id_to_ast_expr.c
+  isl_id_to_id.c
+  isl_id_to_pw_aff.c
+  isl_ilp.c
+  isl_imath.c
+  isl_input.c
+  isl_int_sioimath.c
+  isl_local.c
+  isl_local_space.c
+  isl_lp.c
+  isl_map.c
+  isl_map_list.c
+  isl_map_simplify.c
+  isl_map_subtract.c
+  isl_map_to_basic_set.c
+  isl_mat.c
+  isl_morph.c
+  isl_obj.c
+  isl_options.c
+  isl_output.c
+  isl_point.c
+  isl_polynomial.c
+  isl_printer.c
+  isl_range.c
+  isl_reordering.c
+  isl_sample.c
+  isl_scan.c
+  isl_schedule.c
+  isl_schedule_band.c
+  isl_schedule_constraints.c
+  isl_schedule_node.c
+  isl_schedule_read.c
+  isl_schedule_tree.c
+  isl_scheduler.c
+  isl_seq.c
+  isl_set_list.c
+  isl_sort.c
+  isl_space.c
+  isl_stream.c
+  isl_tab.c
+  isl_tab_pip.c
+  isl_tarjan.c
+  isl_transitive_closure.c
+  isl_union_map.c
+  isl_val.c
+  isl_val_sioimath.c
+  isl_vec.c
+  isl_version.c
+  isl_vertices.c
+  print.c
+  imath/gmp_compat.c
+  imath/imath.c
+  imath/imrat.c
+  )
+
+set(ISL_FILES_PATHS)
+foreach (srcfile IN LISTS ISL_FILES)
+  list(APPEND ISL_FILES_PATHS "${ISL_SOURCE_DIR}/${srcfile}")
+endforeach ()
+
+add_llvm_library(LLVMISL
+    ${ISL_FILES_PATHS}
+  ADDITIONAL_HEADER_DIRS
+    "${LLVM_MAIN_SRC_DIR}/contrib/isl/include"
+    "${ISL_BINARY_DIR}"
+  )
+
+# isl requires at least C99 to compile. gcc < 5.0 uses -std=gnu89 as default.
+set_target_properties(LLVMISL PROPERTIES C_STANDARD 99)
+
+target_include_directories(LLVMISL
+  PRIVATE
+    "${ISL_BINARY_DIR}"
+    "${ISL_BINARY_DIR}/include"
+    "${ISL_SOURCE_DIR}"
+    "${ISL_SOURCE_DIR}/imath"
+  PUBLIC
+    $<BUILD_INTERFACE:${ISL_BINARY_DIR}/include>
+    $<BUILD_INTERFACE:${ISL_SOURCE_DIR}/include>
+	  $<INSTALL_INTERFACE:llvm/ISL>
+  )
+
+# Disable warnings for upstream project.
+set(ISL_DISABLE_WARNINGS_FLAGS)
+if (MSVC)
+  set(ISL_DISABLE_WARNINGS_FLAGS
+    -wd4018 # 'expression' : signed/unsigned mismatch
+    -wd4090 # 'operation' : different 'modifier' qualifiers
+    -wd4200 # nonstandard extension used: zero-sized array in struct/union
+    -wd4201 # nonstandard extension used: nameless struct/union
+    -wd4334 # 'operator': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
+    -wd4221 # nonstandard extension used : 'identifier' : cannot be initialized using address of automatic variable
+    )
+elseif (CMAKE_COMPILER_IS_GNUCC OR CMAKE_CXX_COMPILER MATCHES ".*clang")
+  set(ISL_DISABLE_WARNINGS_FLAGS -w)
+endif ()
+target_compile_options(LLVMISL PRIVATE ${ISL_DISABLE_WARNINGS_FLAGS})
+
+if (LLVM_INCLUDE_TESTS)
+	set(LLVM_LINK_COMPONENTS ISL)
+	add_llvm_executable(isl-test
+	  IGNORE_EXTERNALIZE_DEBUGINFO NO_INSTALL_RPATH
+	  "${ISL_SOURCE_DIR}/isl_test.c"
+	  )
+
+  # isl-test needs access to private headers.
+	target_include_directories(isl-test
+	  PRIVATE
+        "${ISL_BINARY_DIR}"
+        "${ISL_BINARY_DIR}/include"
+        "${ISL_SOURCE_DIR}"
+        "${ISL_SOURCE_DIR}/imath"
+	  )
+
+	target_compile_options(isl-test PRIVATE ${ISL_DISABLE_WARNINGS_FLAGS})
+endif ()
Index: lib/ISL/LLVMBuild.txt
===================================================================
--- lib/ISL/LLVMBuild.txt
+++ lib/ISL/LLVMBuild.txt
@@ -1,4 +1,4 @@
-;===- ./lib/LLVMBuild.txt --------------------------------------*- Conf -*--===;
+;===- ./lib/isl/LLVMBuild.txt ----------------------------------*- Conf -*--===;
 ;
 ;                     The LLVM Compiler Infrastructure
 ;
@@ -15,37 +15,8 @@
 ;
 ;===------------------------------------------------------------------------===;
 
-[common]
-subdirectories =
- Analysis
- AsmParser
- Bitcode
- CodeGen
- DebugInfo
- Demangle
- ExecutionEngine
- FuzzMutate
- LineEditor
- Linker
- IR
- IRReader
- LTO
- MC
- Object
- BinaryFormat
- ObjectYAML
- Option
- Passes
- ProfileData
- Support
- TableGen
- Target
- Testing
- ToolDrivers
- Transforms
- WindowsManifest
-
 [component_0]
-type = Group
-name = Libraries
-parent = $ROOT
+type = Library
+name = ISL
+parent = Libraries
+required_libraries =
Index: lib/ISL/gitversion.h.cmake
===================================================================
--- /dev/null
+++ lib/ISL/gitversion.h.cmake
@@ -0,0 +1 @@
+#define GIT_HEAD_ID "@ISL_GIT_HEAD_ID@"
Index: lib/ISL/isl_config.h.cmake
===================================================================
--- /dev/null
+++ lib/ISL/isl_config.h.cmake
@@ -0,0 +1,51 @@
+/* define if your compiler has __attribute__ */
+#cmakedefine HAVE___ATTRIBUTE__ /**/
+
+/* most gcc compilers know a function __attribute__((__warn_unused_result__)) */
+#define GCC_WARN_UNUSED_RESULT @GCC_WARN_UNUSED_RESULT@
+
+/* Define to 1 if you have the declaration of `ffs', and to 0 if you don't. */
+#define HAVE_DECL_FFS @HAVE_DECL_FFS@
+
+/* Define to 1 if you have the declaration of `__builtin_ffs', and to 0 if you
+   don't. */
+#define HAVE_DECL___BUILTIN_FFS @HAVE_DECL___BUILTIN_FFS@
+
+/* Define to 1 if you have the declaration of `_BitScanForward', and to 0 if
+   you don't. */
+#define HAVE_DECL__BITSCANFORWARD @HAVE_DECL__BITSCANFORWARD@
+
+/* Define to 1 if you have the declaration of `strcasecmp', and to 0 if you
+   don't. */
+#define HAVE_DECL_STRCASECMP @HAVE_DECL_STRCASECMP@
+
+/* Define to 1 if you have the declaration of `_stricmp', and to 0 if you
+   don't. */
+#define HAVE_DECL__STRICMP @HAVE_DECL__STRICMP@
+
+/* Define to 1 if you have the declaration of `strncasecmp', and to 0 if you
+   don't. */
+#define HAVE_DECL_STRNCASECMP @HAVE_DECL_STRNCASECMP@
+
+/* Define to 1 if you have the declaration of `_strnicmp', and to 0 if you
+   don't. */
+#define HAVE_DECL__STRNICMP @HAVE_DECL__STRNICMP@
+
+/* Define to 1 if you have the declaration of `snprintf', and to 0 if you
+   don't. */
+#define HAVE_DECL_SNPRINTF @HAVE_DECL_SNPRINTF@
+
+/* Define to 1 if you have the declaration of `_snprintf', and to 0 if you
+   don't. */
+#define HAVE_DECL__SNPRINTF @HAVE_DECL__SNPRINTF@
+
+/* use gmp to implement isl_int */
+#cmakedefine USE_GMP_FOR_MP
+
+/* use imath to implement isl_int */
+#cmakedefine USE_IMATH_FOR_MP
+
+/* Use small integer optimization */
+#cmakedefine USE_SMALL_INT_OPT
+
+#include <isl_config_post.h>
Index: lib/ISL/isl_srcdir.c.cmake
===================================================================
--- /dev/null
+++ lib/ISL/isl_srcdir.c.cmake
@@ -0,0 +1 @@
+static const char *srcdir = "@ISL_SOURCE_DIR@";
Index: lib/ISL/stdint.h.cmake
===================================================================
--- /dev/null
+++ lib/ISL/stdint.h.cmake
@@ -0,0 +1 @@
+#include <@INCLUDE_STDINT_H@>
Index: lib/LLVMBuild.txt
===================================================================
--- lib/LLVMBuild.txt
+++ lib/LLVMBuild.txt
@@ -44,6 +44,7 @@
  ToolDrivers
  Transforms
  WindowsManifest
+ ISL
 
 [component_0]
 type = Group
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -117,6 +117,10 @@
   set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} LTO)
 endif()
 
+if (TARGET ISL)
+  set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} isl-test)
+endif()
+
 if(LLVM_BUILD_EXAMPLES)
   list(APPEND LLVM_TEST_DEPENDS
     Kaleidoscope-Ch3
Index: test/UnitISL/isl-test.test
===================================================================
--- /dev/null
+++ test/UnitISL/isl-test.test
@@ -0,0 +1 @@
+; RUN: isl-test
Index: tools/llvm-config/BuildVariables.inc.in
===================================================================
--- tools/llvm-config/BuildVariables.inc.in
+++ tools/llvm-config/BuildVariables.inc.in
@@ -35,3 +35,4 @@
 #define LLVM_DYLIB_VERSION "@LLVM_DYLIB_VERSION@"
 #define LLVM_HAS_GLOBAL_ISEL @LLVM_HAS_GLOBAL_ISEL@
 #define LLVM_TOOLS_INSTALL_DIR "@LLVM_TOOLS_INSTALL_DIR@"
+#define LLVM_INCLUDE_ISL @LLVM_INCLUDE_ISL@
Index: tools/llvm-config/CMakeLists.txt
===================================================================
--- tools/llvm-config/CMakeLists.txt
+++ tools/llvm-config/CMakeLists.txt
@@ -49,7 +49,8 @@
   LLVM_LINK_LLVM_DYLIB
   LLVM_HAS_RTTI
   LLVM_HAS_GLOBAL_ISEL
-  BUILD_SHARED_LIBS)
+  BUILD_SHARED_LIBS
+  LLVM_INCLUDE_ISL)
 configure_file(${BUILDVARIABLES_SRCPATH} ${BUILDVARIABLES_OBJPATH} @ONLY)
 
 # Set build-time environment(s).
Index: tools/llvm-config/llvm-config.cpp
===================================================================
--- tools/llvm-config/llvm-config.cpp
+++ tools/llvm-config/llvm-config.cpp
@@ -330,6 +330,11 @@
     // We need to include files from both the source and object trees.
     ActiveIncludeOption =
         ("-I" + ActiveIncludeDir + " " + "-I" + ActiveObjRoot + "/include");
+#if LLVM_INCLUDE_ISL
+    ActiveIncludeOption +=
+        (" -I" + std::string(LLVM_SRC_ROOT) + "/contrib/isl/include" + " -I" +
+         ActiveLibDir + "/ISL/isl/include");
+#endif
   } else {
     ActivePrefix = CurrentExecPrefix;
     ActiveIncludeDir = ActivePrefix + "/include";
@@ -338,7 +343,10 @@
     ActiveBinDir = path.str();
     ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
     ActiveCMakeDir = ActiveLibDir + "/cmake/llvm";
-    ActiveIncludeOption = "-I" + ActiveIncludeDir;
+    ActiveIncludeOption = ActiveIncludeOption = "-I" + ActiveIncludeDir;
+#if LLVM_INCLUDE_ISL
+    ActiveIncludeOption += " -I" + ActiveIncludeDir + "/llvm/ISL";
+#endif
   }
 
   /// We only use `shared library` mode in cases where the static library form