Add optimize_wasm build option for Web

Author: adamscott

platform/web/SCsub

@@ -118,7 +118,15 @@ js_wrapped = env.NoCache(
     env.Textfile("#bin/godot", [env.File(f) for f in wrap_list], TEXTFILESUFFIX="${PROGSUFFIX}.wrapped.js")
 )
 
+main_wasm = build[1]
+side_wasm = build[2] if len(build) > 2 else None
+
+if env["optimize_wasm"]:
+    main_wasm = env.OptimizeWASM(main_wasm)
+    if side_wasm is not None:
+        side_wasm = env.OptimizeWASM(side_wasm)
+
 # 0 - unwrapped js file (use wrapped one instead)
 # 1 - wasm file
 # 2 - wasm side (when dlink is enabled).
-env.CreateTemplateZip(js_wrapped, build[1], build[2] if len(build) > 2 else None)
+env.CreateTemplateZip(js_wrapped, main_wasm, side_wasm)

platform/web/detect.py

@@ -10,6 +10,7 @@
     create_template_zip,
     get_template_zip_path,
     run_closure_compiler,
+    run_optimize_wasm,
 )
 from SCons.Util import WhereIs
 
@@ -57,6 +58,11 @@ def get_opts():
             "Use Emscripten PROXY_TO_PTHREAD option to run the main application code to a separate thread",
             False,
         ),
+        BoolVariable(
+            "optimize_wasm",
+            "Use binaryen `wasm-opt` to reduce the output .wasm file sizes",
+            False,
+        ),
     ]
 
 
@@ -303,3 +309,9 @@ def configure(env: "SConsEnvironment"):
     # This workaround creates a closure that prevents the garbage collector from freeing the WebGL context.
     # We also only use WebGL2, and changing context version is not widely supported anyway.
     env.Append(LINKFLAGS=["-sGL_WORKAROUND_SAFARI_GETCONTEXT_BUG=0"])
+
+    # Optimize WASM file
+    if env["optimize_wasm"]:
+        optimize_wasm_action = env.Action(run_optimize_wasm)
+        optimize_wasm_builder = env.Builder(action=optimize_wasm_action, suffix=".opt.wasm", src_suffix=".wasm")
+        env.Append(BUILDERS={"OptimizeWASM": optimize_wasm_builder})

platform/web/emscripten_helpers.py

@@ -1,8 +1,11 @@
 import json
 import os
+import subprocess
 
-from SCons.Util import WhereIs
+from SCons.Errors import UserError
+from SCons.Util import WhereIs, splitext
 
+from misc.utility.color import print_info
 from platform_methods import get_build_version
 
 
@@ -127,3 +130,19 @@ def add_js_pre(env, js_pre):
 
 def add_js_externs(env, externs):
     env.Append(JS_EXTERNS=env.File(externs))
+
+
+def run_optimize_wasm(target, source, env):
+    wasmopt_bin_path = WhereIs("wasm-opt")
+    if wasmopt_bin_path is None:
+        raise UserError(
+            '[wasm-opt] Cannot find `wasm-opt` command line utility. That binary is usually packed with the "binaryen" package.'
+        )
+
+    for s in source:
+        source_path = str(s)
+        target_path = splitext(source_path)[0] + ".opt.wasm"
+
+        if target_path in [str(t) for t in target]:
+            print_info(f"[wasm-opt] Optimizing {source_path}")
+            subprocess.run([wasmopt_bin_path, source_path, "-o", target_path, "-all", "--post-emscripten", "-Oz"])