Index: lib/External/CMakeLists.txt
===================================================================
--- lib/External/CMakeLists.txt
+++ lib/External/CMakeLists.txt
@@ -262,6 +262,22 @@
   ${ISL_FILES}
 )
 
+
+# TODO: use system isl instead
+if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+  set(POLLY_ISL_HEADER_PREFIX "include/polly" CACHE STRING
+    "Install prefix for the isl headers")
+  mark_as_advanced(POLLY_ISL_HEADER_PREFIX)
+
+  install(DIRECTORY ${ISL_SOURCE_DIR}/include/
+    DESTINATION ${POLLY_ISL_HEADER_PREFIX}
+    FILES_MATCHING
+    PATTERN "*.h"
+    PATTERN "CMakeFiles" EXCLUDE
+    PATTERN ".svn" EXCLUDE
+    )
+endif()
+
 add_executable(polly-isl-test
   isl/isl_test.c
 )