do not save debug info if js opts will remove it anyhow

emcc

@@ -1456,8 +1456,9 @@ try:
 
   # Request LLVM debug info if explicitly specified, or building bitcode with -g, or if building a source all the way to JS with -g
   if debug_level >= 4 or ((final_suffix not in JS_CONTAINING_SUFFIXES or (has_source_inputs and final_suffix in JS_CONTAINING_SUFFIXES)) and requested_debug == '-g'):
-    newargs.append('-g') # preserve LLVM debug info
-    debug_level = 4
+    if not (final_suffix in JS_CONTAINING_SUFFIXES and js_opts): # do not save llvm debug info if js optimizer will wipe it out anyhow
+      newargs.append('-g') # preserve LLVM debug info
+      debug_level = 4
 
   # First, generate LLVM bitcode. For each input file, we get base.o with bitcode
   for i, input_file in input_files:

tests/test_other.py

@@ -1940,14 +1940,15 @@ int f() {
     if os.environ.get('EMCC_DEBUG'): return self.skip('cannot run in debug mode')
     try:
       os.environ['EMCC_DEBUG'] = '1'
-      # llvm debug info is kept only when we can see it, which is without the js optimize, -O0. js debug info is lost by registerize in -O2, so - g disables it
       for args, expect_llvm, expect_js in [
-          (['-O0'], True, True),
+          (['-O0'], False, True),
           (['-O0', '-g'], True, True),
+          (['-O0', '-g4'], True, True),
           (['-O1'], False, True),
-          (['-O1', '-g'], False, True),
+          (['-O1', '-g'], True, True),
           (['-O2'], False, False),
-          (['-O2', '-g'], False, True),
+          (['-O2', '-g'], False, True), # drop llvm debug info as js opts kill it anyway
+          (['-O2', '-g4'], True, True), # drop llvm debug info as js opts kill it anyway
         ]:
         print args, expect_llvm, expect_js
         output, err = Popen([PYTHON, EMCC, path_from_root('tests', 'hello_world.cpp')] + args, stdout=PIPE, stderr=PIPE).communicate()