Add CMake option to explicitly skip wasm-opt and use `wasm-tools stri…

…p` instead. (#89)

As per #8, it seems the main purpose of using wasm-opt was to reduce
module size by stripping debug sections. The comment in the CMake file
also indicates an intent to optimize the binary.

However, `wasm-opt -O3` is extremely expensive on large programs; on
my 18-core, 36-thread workstation, it took several minutes to
complete. This is very painful when part of a debug loop that requires
release builds (e.g. for performance features).

This PR adds a `USE_WASM_OPT` CMake option, on by default to preserve
existing behavior, that allows one to do `cmake
-DCMAKE_BUILD_TYPE=Release -DUSE_WASM_OPT=OFF` to get a release build
without `wasm-opt`. In its place, this PR uses `wasm-tools strip -a`,
which strips debug sections (and all other custom sections) without
rewriting code.

CMakeLists.txt

@@ -58,24 +58,36 @@ add_executable(starling.wasm
         runtime/script_loader.cpp
 )
 
+option(USE_WASM_OPT "use wasm-opt to optimize the StarlingMonkey binary" ON)
+
 # For release builds, use wasm-opt to optimize the generated wasm file.
-if (CMAKE_BUILD_TYPE STREQUAL "Release")
-    add_custom_command(
-            TARGET starling.wasm
-            POST_BUILD
-            COMMAND ${WASM_OPT} --strip-debug -O3 -o starling.wasm starling.wasm
-            WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
-    )
-elseif (CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
-    add_custom_command(
+if (USE_WASM_OPT)
+    if (CMAKE_BUILD_TYPE STREQUAL "Release")
+        add_custom_command(
+                TARGET starling.wasm
+                POST_BUILD
+                COMMAND ${WASM_OPT} --strip-debug -O3 -o starling.wasm starling.wasm
+                WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        )
+    elseif (CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
+        add_custom_command(
+                TARGET starling.wasm
+                POST_BUILD
+                COMMAND ${WASM_OPT} -O3 -o starling.wasm starling.wasm
+                WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        )
+    endif()
+else()
+    if (CMAKE_BUILD_TYPE STREQUAL "Release")
+        add_custom_command(
             TARGET starling.wasm
             POST_BUILD
-            COMMAND ${WASM_OPT} -O3 -o starling.wasm starling.wasm
+            COMMAND ${WASM_TOOLS_BIN} strip -a -o starling.wasm starling.wasm
             WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
-    )
+        )
+    endif()
 endif()
 
-
 target_link_libraries(starling.wasm PRIVATE host_api extension_api builtins spidermonkey rust-url)
 
 set(RUNTIME_FILE "starling.wasm")

cmake/wasm-tools.cmake

@@ -3,3 +3,4 @@ set(WASM_TOOLS_VERSION 1.0.54)
 set(WASM_TOOLS_URL https://github.com/bytecodealliance/wasm-tools/releases/download/wasm-tools-${WASM_TOOLS_VERSION}/wasm-tools-${WASM_TOOLS_VERSION}-${HOST_ARCH}-${HOST_OS}.tar.gz)
 CPMAddPackage(NAME wasm-tools URL ${WASM_TOOLS_URL} DOWNLOAD_ONLY TRUE)
 set(WASM_TOOLS_DIR ${CPM_PACKAGE_wasm-tools_SOURCE_DIR})
+set(WASM_TOOLS_BIN ${WASM_TOOLS_DIR}/wasm-tools)