CMake: Add support with Swiftshader with DAWN_ENABLE_SWIFTSHADER

Change-Id: I2b3d906bac760a22f33104231a6341415cbff3b5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/85365
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 060bac9..2d7d0ee 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -128,6 +128,7 @@
 
 option_if_not_defined(DAWN_BUILD_SAMPLES "Enables building Dawn's samples" ${BUILD_SAMPLES})
 option_if_not_defined(DAWN_BUILD_NODE_BINDINGS "Enables building Dawn's NodeJS bindings" OFF)
+option_if_not_defined(DAWN_ENABLE_SWIFTSHADER "Enables building Swiftshader as part of the build and Vulkan adapter discovery" OFF)
 
 option_if_not_defined(DAWN_ENABLE_PIC "Build with Position-Independent-Code enabled" OFF)
 
@@ -141,6 +142,7 @@
 set_if_not_defined(DAWN_JINJA2_DIR "${DAWN_THIRD_PARTY_DIR}/jinja2" "Directory in which to find Jinja2")
 set_if_not_defined(DAWN_SPIRV_HEADERS_DIR "${DAWN_THIRD_PARTY_DIR}/vulkan-deps/spirv-headers/src" "Directory in which to find SPIRV-Headers")
 set_if_not_defined(DAWN_SPIRV_TOOLS_DIR "${DAWN_THIRD_PARTY_DIR}/vulkan-deps/spirv-tools/src" "Directory in which to find SPIRV-Tools")
+set_if_not_defined(DAWN_SWIFTSHADER_DIR "${DAWN_THIRD_PARTY_DIR}/swiftshader" "Directory in which to find swiftshader")
 set_if_not_defined(DAWN_TINT_DIR "${Dawn_SOURCE_DIR}" "Directory in which to find Tint")
 set_if_not_defined(DAWN_VULKAN_DEPS_DIR "${DAWN_THIRD_PARTY_DIR}/vulkan-deps" "Directory in which to find vulkan-deps")
 set_if_not_defined(DAWN_VULKAN_HEADERS_DIR "${DAWN_VULKAN_DEPS_DIR}/vulkan-headers/src" "Directory in which to find Vulkan-Headers")

src/dawn/native/CMakeLists.txt

diff --git a/src/dawn/native/CMakeLists.txt b/src/dawn/native/CMakeLists.txt
index e7cab14..d695c20 100644
--- a/src/dawn/native/CMakeLists.txt
+++ b/src/dawn/native/CMakeLists.txt
@@ -442,6 +442,10 @@
     target_link_libraries(dawn_native PRIVATE dawn_khronos_platform)
 endif()
 
+if (DAWN_ENABLE_SWIFTSHADER)
+    target_compile_definitions(dawn_native PRIVATE "DAWN_ENABLE_SWIFTSHADER")
+endif()
+
 if (DAWN_ENABLE_VULKAN)
     target_sources(dawn_native PRIVATE
         "${DAWN_INCLUDE_DIR}/dawn/native/VulkanBackend.h"

third_party/CMakeLists.txt

diff --git a/third_party/CMakeLists.txt b/third_party/CMakeLists.txt
index bc75898..d516352 100644
--- a/third_party/CMakeLists.txt
+++ b/third_party/CMakeLists.txt
@@ -96,6 +96,14 @@
 )
 target_include_directories(dawn_vulkan_headers INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/khronos")
 
+if (${DAWN_ENABLE_SWIFTSHADER} AND NOT TARGET vk_swiftshader)
+    set(SWIFTSHADER_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+    set(SWIFTSHADER_BUILD_BENCHMARKS OFF CACHE BOOL "" FORCE)
+
+    message(STATUS "Dawn: using Swiftshader at ${DAWN_SWIFTSHADER_DIR}")
+    add_subdirectory(${DAWN_SWIFTSHADER_DIR} "${CMAKE_CURRENT_BINARY_DIR}/swiftshader")
+endif()
+
 if (${TINT_BUILD_BENCHMARKS})
   set(BENCHMARK_ENABLE_TESTING FALSE CACHE BOOL FALSE FORCE)
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/benchmark EXCLUDE_FROM_ALL)