Update build to allow setting external paths (#6528)

* Update build to allow setting external paths

Update the build to allow setting user-specific paths for the external modules.
This allows building Slang without also fetching the external modules, assuming
they are already present elsewhere locally.

5 files changed, 130 insertions, 13 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 48d263d14..a74047e0f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -166,6 +166,43 @@ option(
 )
 mark_as_advanced(SLANG_SPIRV_HEADERS_INCLUDE_DIR)
 
+# Options for user defined paths for external modules.
+advanced_option(
+    SLANG_OVERRIDE_LZ4_PATH
+    "Build using user defined path for LZ4"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_MINIZ_PATH
+    "Build using user defined path for Miniz"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_UNORDERED_DENSE_PATH
+    "Build using user defined path for unordered_dense"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_VULKAN_HEADERS_PATH
+    "Build using user defined path for Vulkan headers"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_SPIRV_HEADERS_PATH
+    "Build using user defined path for SPIR-V headers"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_SPIRV_TOOLS_PATH
+    "Build using user defined path for SPIR-V tools"
+    OFF
+)
+advanced_option(
+    SLANG_OVERRIDE_GLSLANG_PATH
+    "Build using user defined path for glslang, this also requires "
+    OFF
+)
+
 if(${SLANG_USE_SYSTEM_LZ4})
     add_compile_definitions(SLANG_USE_SYSTEM_LZ4_HEADER)
 endif()
@@ -178,6 +215,10 @@ if(${SLANG_USE_SYSTEM_UNORDERED_DENSE})
     add_compile_definitions(SLANG_USE_SYSTEM_UNORDERED_DENSE_HEADER)
 endif()
 
+if(SLANG_OVERRIDE_SPIRV_HEADERS_PATH)
+    add_compile_definitions(SLANG_USE_SYSTEM_SPIRV_HEADER)
+endif()
+
 enum_option(
     SLANG_LIB_TYPE
     # Default
diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index f23027f68..a590fe538 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -27,13 +27,32 @@ if(NOT SLANG_ENABLE_EXTERNAL_COMPILER_WARNINGS)
     endif()
 endif()
 
+# Unordered dense
 if(NOT ${SLANG_USE_SYSTEM_UNORDERED_DENSE})
-    add_subdirectory(unordered_dense EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_UNORDERED_DENSE_PATH)
+        add_subdirectory(unordered_dense EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_UNORDERED_DENSE_PATH}
+            unordered_dense
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
 endif()
 
 # Miniz
 if(NOT ${SLANG_USE_SYSTEM_MINIZ})
-    add_subdirectory(miniz EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_MINIZ_PATH)
+        add_subdirectory(miniz EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_MINIZ_PATH}
+            miniz
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
     set_property(TARGET miniz PROPERTY POSITION_INDEPENDENT_CODE ON)
     # Work around https://github.com/richgel999/miniz/pull/292
     get_target_property(miniz_c_launcher miniz C_COMPILER_LAUNCHER)
@@ -46,7 +65,16 @@ endif()
 # LZ4
 if(NOT ${SLANG_USE_SYSTEM_LZ4})
     set(LZ4_BUNDLED_MODE ON)
-    add_subdirectory(lz4/build/cmake EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_LZ4_PATH)
+        add_subdirectory(lz4/build/cmake EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_LZ4_PATH}/build/cmake
+            lz4/build/cmake
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
     if(MSVC)
         target_compile_options(
             lz4_static
@@ -57,7 +85,16 @@ endif()
 
 # Vulkan headers
 if(NOT ${SLANG_USE_SYSTEM_VULKAN_HEADERS})
-    add_subdirectory(vulkan EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_VULKAN_HEADERS_PATH)
+        add_subdirectory(vulkan EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_VULKAN_HEADERS_PATH}
+            vulkan
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
 endif()
 
 # metal-cpp headers
@@ -69,22 +106,55 @@ target_include_directories(
 
 # SPIRV-Headers
 if(NOT ${SLANG_USE_SYSTEM_SPIRV_HEADERS})
-    add_subdirectory(spirv-headers EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_SPIRV_HEADERS_PATH)
+        add_subdirectory(spirv-headers EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_SPIRV_HEADERS_PATH}
+            spirv-headers
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
 endif()
 
 if(SLANG_ENABLE_SLANG_GLSLANG)
     # SPIRV-Tools
     set(SPIRV_TOOLS_BUILD_STATIC ON)
     set(SPIRV_WERROR OFF)
-    set(SPIRV_HEADER_DIR "${CMAKE_CURRENT_LIST_DIR}/spirv-headers/")
+    # Headers
+    if(NOT SLANG_OVERRIDE_SPIRV_HEADERS_PATH)
+        set(SPIRV_HEADER_DIR "${CMAKE_CURRENT_LIST_DIR}/spirv-headers/")
+    else()
+        set(SPIRV_HEADER_DIR ${SLANG_OVERRIDE_SPIRV_HEADERS_PATH})
+    endif()
     set(SPIRV_SKIP_TESTS ON)
-    add_subdirectory(spirv-tools EXCLUDE_FROM_ALL ${system})
+    # Tools
+    if(NOT SLANG_OVERRIDE_SPIRV_TOOLS_PATH)
+        add_subdirectory(spirv-tools EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_SPIRV_TOOLS_PATH}
+            spirv-tools
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
 
     # glslang
     set(SKIP_GLSLANG_INSTALL ON)
     set(ENABLE_OPT ON)
     set(ENABLE_PCH OFF)
-    add_subdirectory(glslang EXCLUDE_FROM_ALL ${system})
+    if(NOT SLANG_OVERRIDE_GLSLANG_PATH)
+        add_subdirectory(glslang EXCLUDE_FROM_ALL ${system})
+    else()
+        add_subdirectory(
+            ${SLANG_OVERRIDE_GLSLANG_PATH}
+            glslang
+            EXCLUDE_FROM_ALL
+            ${system}
+        )
+    endif()
 endif()
 
 # imgui
diff --git a/source/core/slang-dictionary.h b/source/core/slang-dictionary.h
index 79f6dee30..639978a08 100644
--- a/source/core/slang-dictionary.h
+++ b/source/core/slang-dictionary.h
@@ -1,7 +1,6 @@
 #ifndef SLANG_CORE_DICTIONARY_H
 #define SLANG_CORE_DICTIONARY_H
 
-#include "../../external/unordered_dense/include/ankerl/unordered_dense.h"
 #include "slang-common.h"
 #include "slang-exception.h"
 #include "slang-hash.h"
@@ -10,6 +9,7 @@
 #include "slang-math.h"
 #include "slang-uint-set.h"
 
+#include <ankerl/unordered_dense.h>
 #include <initializer_list>
 
 namespace Slang
diff --git a/source/core/slang-hash.h b/source/core/slang-hash.h
index ebe3d1973..eee58878b 100644
--- a/source/core/slang-hash.h
+++ b/source/core/slang-hash.h
@@ -1,10 +1,10 @@
 #ifndef SLANG_CORE_HASH_H
 #define SLANG_CORE_HASH_H
 
-#include "../../external/unordered_dense/include/ankerl/unordered_dense.h"
 #include "slang-math.h"
 #include "slang.h"
 
+#include <ankerl/unordered_dense.h>
 #include <cstring>
 #include <type_traits>
 
diff --git a/source/slang/CMakeLists.txt b/source/slang/CMakeLists.txt
index b9e78407b..9c51ed767 100644
--- a/source/slang/CMakeLists.txt
+++ b/source/slang/CMakeLists.txt
@@ -110,9 +110,15 @@ target_include_directories(
 #
 
 if(NOT SLANG_USE_SYSTEM_SPIRV_HEADERS)
-    set(SLANG_SPIRV_HEADERS_INCLUDE_DIR
-        "${slang_SOURCE_DIR}/external/spirv-headers/include"
-    )
+    if(NOT SLANG_OVERRIDE_SPIRV_HEADERS_PATH)
+        set(SLANG_SPIRV_HEADERS_INCLUDE_DIR
+            "${slang_SOURCE_DIR}/external/spirv-headers/include"
+        )
+    else()
+        set(SLANG_SPIRV_HEADERS_INCLUDE_DIR
+            "${SLANG_OVERRIDE_SPIRV_HEADERS_PATH}/include"
+        )
+    endif()
 endif()
 
 set(SLANG_LOOKUP_GENERATOR_INPUT_JSON