Add isl to LLVM repository.

[Meinersbur]

Summary

Add the integer set library ("isl", http://isl.gforge.inria.fr, MIT-licensed) into the contrib/isl directory and add a new component "LLVMISL".

The integer set library contains functions for polyhedral (integer and rational) vector sets and program transformations. Polly uses it to implement its analysis and optimization. The isl source is already included in Polly (in lib/External/isl) and this patch is derived from that. For upstreaming Polly into the main LLVM repository, it is necessary to include isl as well.

This is marked as Work-In-Progress; depending on feedback given the following might be added:

• An option to use the isl installed on the host system
• Polly requires an additional header file isl-noexecptions.h which is a C++ wrapper around isl's C API. It is generated from the public headers using a python script by make dist. However, vanilla isl only generates a version that does not contain all functionality required by Polly. We are working upstream to change that, but in the meantime Polly comes with its own isl-noexceptions.h, i.e. Polly keeps a slightly modified version of isl that requires merging ("merging" here means that we just discard isl's isl-noexceptions.h und use Polly's). I did not integrate this file in this patch, we can either maintain a slightly modified version of isl, or put our custom isl-noexceptions.h in a different folder.

Decision rationales:

• The library is named LLVMISL and contained in the lib/ISL folder to work best with LLVM's component system. The component's name "ISL" was chosen over "isl" as it matches the capitalization of other two/three-letter-acronym components.

• Isl's headers are installed into $PREFIX/include/llvm/ISL/isl. This is to not conflict with potentially user/system-installed isl headers. Please note that this means that MIT-licensed headers land on the target system.

• The source of isl itself is added to the contrib/isl directory. This is to keep the source in one directory rather than spreading it into the lib and include directories, facilitating integration of upstream changes. There is a script "isl-merge.py" that automates this. It currently requires LLVM being checked out using git. The new subfolder "contrib" should make it clear that this is downstream code and maybe one shouldn't run clang-format over it which would make the next merge difficult.

• There is an additional "GIT_HEAD_ID" file containing the upstream's revision. It is used by isl-merge.py to determine the common ancestor and CMakeLists.txt to determine the version. Normally isl's make dist would generate this file, it is done manually here to not require a configure/make/make dist cycle when merging the latest isl. Due to different Autotools versions being installed on the different systems, this might lead to spurious conflicts with the generated configure etc. files. However, due to the need of an isl-noexeceptions.h, I may need to include such a cycle in isl-merge.py anyway.

• Isl has its own unittest "isl_test.c". It is put into bin/ (but not installed) and run by llvm-lit on llvm-check. This was just the simplest to do since it doesn't require any additional lit.site.cfg in order to find the isl_test in a different directory.

[Eugene.Zelenko]

lib/ISL/CMakeLists.txt

55

Please remove duplicated empty line.

90

Please remove duplicated empty line.

105

Please remove duplicated empty line.

120

Please remove duplicated empty line.

135

Please remove duplicated empty line.

152

Please remove duplicated empty line.

159

Please remove duplicated empty line.

285

Please remove duplicated empty line.

lib/ISL/isl_config.h.cmake

6

Please remove duplicated empty line.

18

Please remove duplicated empty line.

27

Please remove duplicated empty line.

36

Please remove duplicated empty line.

45

Please remove duplicated empty line.

[Meinersbur]

Remove duplicated empty lines.

[philip.pfaffe]

I think this should be an RFC on llvm-dev. This needs a wider audience and a discussion that goes beyond the technical.

[Meinersbur]

• Include isl conditionally using LLVM_INCLUDE_ISL (defaults to OFF)
• Fix include paths (llvm-config and install)
• Use -w flag only for gcc/clang

CMakeLists.txt

install(DIRECTORY ${LLVM_INCLUDE_DIR}/llvm
     PATTERN "*.gen"
     PATTERN "*.inc"
     # Exclude include/llvm/CMakeFiles/intrinsics_gen.dir, matched by "*.def"
     PATTERN "CMakeFiles" EXCLUDE
     PATTERN "config.h" EXCLUDE
     PATTERN ".svn" EXCLUDE
     )
 
+  install(DIRECTORY contrib/isl/include/isl
+    DESTINATION include/llvm/ISL
+    COMPONENT llvm-headers
+    FILES_MATCHING
+    PATTERN "*.h"
+    )
+
+  install(DIRECTORY ${LLVM_BINARY_DIR}/contrib/isl/include/isl
+    DESTINATION include/llvm/ISL
+    COMPONENT llvm-headers
+    FILES_MATCHING
+    PATTERN "*.h"
+    )
+
   # Installing the headers needs to depend on generating any public
   # tablegen'd headers.
   add_custom_target(llvm-headers DEPENDS intrinsics_gen)
   set_target_properties(llvm-headers PROPERTIES FOLDER "Misc")
 
   if (NOT CMAKE_CONFIGURATION_TYPES)
     add_custom_target(install-llvm-headers
                       DEPENDS llvm-headers

contrib/isl-merge.py

+#! /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 expect the existence 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()

contrib/isl/.gitmodules

-[submodule "imath"]
-  path = imath
-  url = https://github.com/creachadair/imath.git

contrib/isl/GIT_HEAD_ID

+isl-0.18-979-g130e0d9
 No newline at end of file

lib/CMakeLists.txt

 add_subdirectory(AsmParser)
 add_subdirectory(LineEditor)
 add_subdirectory(ProfileData)
 add_subdirectory(Passes)
 add_subdirectory(ToolDrivers)
 add_subdirectory(XRay)
 add_subdirectory(Testing)
 add_subdirectory(WindowsManifest)
+add_subdirectory(ISL)

lib/ISL/CMakeLists.txt

+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.
+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
+  )
+else ()
+  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 ()

lib/ISL/LLVMBuild.txt

+;===- ./lib/isl/LLVMBuild.txt ----------------------------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = ISL
+parent = Libraries
+required_libraries =

lib/ISL/gitversion.h.cmake

+#define GIT_HEAD_ID "@ISL_GIT_HEAD_ID@"

lib/ISL/isl_config.h.cmake

+/* 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>

lib/ISL/isl_srcdir.c.cmake

+static const char *srcdir = "@ISL_SOURCE_DIR@";

lib/ISL/stdint.h.cmake

+#include <@INCLUDE_STDINT_H@>

lib/LLVMBuild.txt

  ProfileData
  Support
  TableGen
  Target
  Testing
  ToolDrivers
  Transforms
  WindowsManifest
+ ISL
 
 [component_0]
 type = Group
 name = Libraries
 parent = $ROOT

test/CMakeLists.txt

set(LLVM_TEST_DEPENDS
           not
           obj2yaml
           opt
           sancov
           sanstats
           verify-uselistorder
           yaml-bench
           yaml2obj
+          isl-test
         )
 
 if(TARGET llvm-lto)
   set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} llvm-lto)
 endif()
 
 # If Intel JIT events are supported, depend on a tool that tests the listener.
 if( LLVM_USE_INTEL_JITEVENTS )

test/UnitISL/isl-test.test

+; RUN: isl-test

tools/llvm-config/llvm-config.cpp

case CMakeBuildModeStyle:
       ActiveLibDir =
           ActiveObjRoot + "/lib" + LLVM_LIBDIR_SUFFIX + "/" + build_mode;
       ActiveCMakeDir = ActiveLibDir + "/cmake/llvm";
       break;
     }
 
     // We need to include files from both the source and object trees.
     ActiveIncludeOption =
-        ("-I" + ActiveIncludeDir + " " + "-I" + ActiveObjRoot + "/include");
+        ("-I" + ActiveIncludeDir + " " + "-I" + ActiveObjRoot + "/include" +
+         " -I" + ActiveIncludeDir + "/contrib/isl/include" + " -I" +
+         ActiveObjRoot + "/llvm/ISL");
   } else {
     ActivePrefix = CurrentExecPrefix;
     ActiveIncludeDir = ActivePrefix + "/include";
     SmallString<256> path(StringRef(LLVM_TOOLS_INSTALL_DIR));
     sys::fs::make_absolute(ActivePrefix, path);
     ActiveBinDir = path.str();
     ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
     ActiveCMakeDir = ActiveLibDir + "/cmake/llvm";
-    ActiveIncludeOption = "-I" + ActiveIncludeDir;
+    ActiveIncludeOption =
+        ("-I" + ActiveIncludeDir + " -I" + ActiveIncludeDir + "/llvm/ISL");
   }
 
   /// We only use `shared library` mode in cases where the static library form
   /// of the components provided are not available; note however that this is
   /// skipped if we're run from within the build dir. However, once installed,
   /// we still need to provide correct output when the static archives are
   /// removed or, as in the case of CMake's `BUILD_SHARED_LIBS`, never present
   /// in the first place. This can't be done at configure/build time.