From 16cb0502e6a117cc2758e69042518a33326107dc Mon Sep 17 00:00:00 2001
From: Connor Baker <connor.baker@tweag.io>
Date: Sat, 20 Jan 2024 20:37:09 +0000
Subject: [PATCH] cmake: make pre-built library discoverable via CMake
 configuration files

Co-Authored-By: Someone Serge <sergei.kozlukov@aalto.fi>
---
 .gitignore              |  1 +
 CMakeLists.txt          | 58 ++++++++++++++++++++++++++++++++---------
 drjit-core-config.cmake |  1 +
 3 files changed, 47 insertions(+), 13 deletions(-)
 create mode 100644 drjit-core-config.cmake

diff --git a/.gitignore b/.gitignore
index aabfccc92..f3a36f602 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 /.clangd
 /compile_commands.json
 *.cmake
+!drjit-core-config.cmake
 CMakeCache.txt
 CMakeFiles
 Makefile
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 02250dbbc..3a0acbcc5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -70,11 +70,42 @@ if (NOT APPLE)
 endif()
 
 # ----------------------------------------------------------
-#  Build the nanothread library
+#  Find or build the dependencies
 # ----------------------------------------------------------
 
-add_subdirectory(ext/nanothread)
-mark_as_advanced(NANOTHREAD_ENABLE_TESTS)
+find_package(nanothread)
+if (NOT nanothread_FOUND)
+  add_subdirectory(ext/nanothread)
+  mark_as_advanced(NANOTHREAD_ENABLE_TESTS)
+endif()
+
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+  pkg_check_modules(lz4 liblz4 IMPORTED_TARGET)
+  add_library(lz4 ALIAS PkgConfig::lz4)
+endif()
+if(NOT lz4_FOUND)
+  add_library(lz4 ext/lz4/lz4.c ext/lz4/xxhash.c)
+  target_include_directories(lz4 PUBLIC ext/lz4)
+endif()
+
+find_package(xxHash)
+if (NOT xxHash_FOUND)
+  add_library(xxhash ext/lz4/xxhash.c)
+  target_include_directories(xxhash PUBLIC ext/lz4)
+
+  add_library(xxHash::xxhash ALIAS xxhash)
+endif()
+
+find_package(tsl-robin-map)
+if (NOT tsl-robin-map_FOUND)
+  add_subdirectory(ext/robin_map)
+endif()
+
+find_package(LLVM)
+if (LLVM_FOUND)
+  target_link_libraries(drjit-core PRIVATE LLVM)
+endif()
 
 # ----------------------------------------------------------
 #  Build Dr.Jit-Core
@@ -135,21 +166,13 @@ add_library(
   src/init.cpp
   src/api.cpp
 
-  # LZ4 compression library & XXHash hash function
-  ext/lz4/lz4.h ext/lz4/lz4.c
-  ext/lz4/xxhash.h ext/lz4/xxh3.h ext/lz4/xxhash.c
-
   # Precompiled kernels in compressed PTX format
   resources/kernels.h resources/kernels.c
 )
 
 target_compile_features(drjit-core PRIVATE cxx_std_17)
 
-target_include_directories(drjit-core PRIVATE
-  ext/nanothread/include
-  ext/robin_map/include
-  ext/lz4
-)
+target_link_libraries(drjit-core PRIVATE nanothread tsl::robin_map lz4 xxHash::xxhash)
 
 if (MSVC)
   # Conditional expression is constant (a few in robin_hash.h)
@@ -170,7 +193,7 @@ target_compile_definitions(drjit-core PRIVATE -DLZ4LIB_VISIBILITY=)
 target_include_directories(drjit-core
   PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+  $<INSTALL_INTERFACE:include>)
 
 target_compile_definitions(drjit-core PRIVATE -DDRJIT_BUILD=1)
 target_link_libraries(drjit-core PRIVATE nanothread)
@@ -229,3 +252,12 @@ set_target_properties(drjit-core PROPERTIES INTERPROCEDURAL_OPTIMIZATION_DEBUG
 if (DRJIT_ENABLE_TESTS)
   add_subdirectory(tests)
 endif()
+
+configure_file(drjit-core-config.cmake "${CMAKE_CURRENT_BINARY_DIR}/drjit-core/drjit-core-config.cmake")
+install(TARGETS drjit-core EXPORT drjit-core-targets INCLUDES DESTINATION include)
+install(DIRECTORY include/drjit-core DESTINATION include)
+install(FILES drjit-core-config.cmake DESTINATION lib/cmake/drjit-core)
+install(
+  EXPORT drjit-core-targets
+  FILE drjit-core-targets.cmake
+  DESTINATION lib/cmake/drjit-core)
diff --git a/drjit-core-config.cmake b/drjit-core-config.cmake
new file mode 100644
index 000000000..0b800fd66
--- /dev/null
+++ b/drjit-core-config.cmake
@@ -0,0 +1 @@
+include("${CMAKE_CURRENT_LIST_DIR}/drjit-core-targets.cmake")