Add WASM build target for Web version of glslang

CMakeLists.txt

@@ -32,6 +32,9 @@ option(ENABLE_HLSL "Enables HLSL input support" ON)
 
 option(ENABLE_OPT "Enables spirv-opt capability if present" ON)
 
+option(ENABLE_GLSLANG_WEB "Reduces glslang to minumum needed for web use" OFF)
+option(ENABLE_EMSCRIPTEN_SINGLE_FILE "If using emscripten, enables SINGLE_FILE build" OFF)
+
 if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT AND WIN32)
     set(CMAKE_INSTALL_PREFIX "install" CACHE STRING "..." FORCE)
 endif()
@@ -98,6 +101,27 @@ elseif(${CMAKE_CXX_COMPILER_ID} MATCHES "MSVC")
     add_compile_options(/GR-) # Disable RTTI
 endif()
 
+if(ENABLE_GLSLANG_WEB)
+    if(EMSCRIPTEN)
+        add_compile_options(-Os -fno-exceptions)
+        add_compile_options("SHELL: -s WASM=1")
+        add_compile_options("SHELL: -s WASM_OBJECT_FILES=0")
+        add_link_options(-Os)
+        add_link_options("SHELL: -s FILESYSTEM=0")
+        add_link_options("SHELL: --llvm-lto 1")
+        add_link_options("SHELL: --closure 1")
+        add_link_options("SHELL: -s ENVIRONMENT=web,worker")
+        add_link_options("SHELL: -s ALLOW_MEMORY_GROWTH=1")
+
+        add_link_options("SHELL: -s MODULARIZE=1")
+        if(ENABLE_EMSCRIPTEN_SINGLE_FILE)
+            add_link_options("SHELL: -s SINGLE_FILE=1")
+        endif(ENABLE_EMSCRIPTEN_SINGLE_FILE)
+    else(EMSCRIPTEN)
+        add_compile_options(-Os -g -flto -fno-exceptions)
+    endif(EMSCRIPTEN)
+endif(ENABLE_GLSLANG_WEB)
+
 # Request C++11
 if(${CMAKE_VERSION} VERSION_LESS 3.1)
     # CMake versions before 3.1 do not understand CMAKE_CXX_STANDARD

HOWTO-build-wasm.md

+Build as usual (see `README.md`), but:
+  * Need `emsdk` in your *PATH*
+    + Instructions located
+      [here](https://emscripten.org/docs/getting_started/downloads.html#sdk-download-and-install)
+  * Do not checkout SPIRV-Tools into External/
+    + Does not work correctly with emscripten out of the box and we don't want
+      it in the build anyway.
+    + *TBD* Add flag to disable SPIRV-Tool inclusion even if directory is
+      present.
+  * Wrap call to `cmake` using `emconfigure`:
+    + e.g. `emconfigure cmake -DCMAKE_BUILD_TYPE=Release -DENABLE_GLSLANG_WEB=ON
+    -DENABLE_HLSL=OFF -DCMAKE_INSTALL_PREFIX="$(pwd)/install" ..`
+    + To get a 'true' size, make sure to use `brotli` to compress the .js and .wasm files
+

glslang/CMakeLists.txt

@@ -122,3 +122,15 @@ if(ENABLE_GLSLANG_INSTALL)
         install(FILES ${file} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/glslang/${dir})
     endforeach()
 endif(ENABLE_GLSLANG_INSTALL)
+
+if(ENABLE_GLSLANG_WEB)
+    add_executable(glslang.js glslang.js.cpp)
+    glslang_set_link_args(glslang.js)
+    target_link_libraries(glslang.js glslang SPIRV)
+    if(EMSCRIPTEN)
+        set_target_properties(glslang.js PROPERTIES
+          OUTPUT_NAME "glslang"
+          SUFFIX ".js"
+          LINK_FLAGS "--bind")
+    endif(EMSCRIPTEN)
+endif(ENABLE_GLSLANG_WEB)