Fix llvm backend debug info with opts (#8298)

We invoke wasm-opt after finalize, and it needs to be given the source map, and told to emit one, as it changes the binary.

This wasn't noticed in testing because finalize did emit a .map file - it just got out of date later when the binary was changed, but the test just checks for its existence and how many items it has, and doesn't literally understand the source map format and check if things line up to the binary.

emcc.py

@@ -956,6 +956,7 @@ def optimizing(opts):
     asm_target = unsuffixed(js_target) + '.asm.js' # might not be used, but if it is, this is the name
     wasm_text_target = asm_target.replace('.asm.js', '.wast') # ditto, might not be used
     wasm_binary_target = asm_target.replace('.asm.js', '.wasm') # ditto, might not be used
+    wasm_source_map_target = wasm_binary_target + '.map'
 
     if final_suffix == '.html' and not options.separate_asm and 'PRECISE_F32=2' in settings_changes:
       options.separate_asm = True
@@ -1925,7 +1926,7 @@ def get_final():
         wasm_temp = temp_basename + '.wasm'
         shutil.move(wasm_temp, wasm_binary_target)
         if use_source_map(options):
-          shutil.move(wasm_temp + '.map', wasm_binary_target + '.map')
+          shutil.move(wasm_temp + '.map', wasm_source_map_target)
 
       if shared.Settings.CYBERDWARF:
         cd_target = final + '.cd'
@@ -2200,7 +2201,8 @@ def get_eliminate():
 
       if shared.Settings.WASM:
         do_binaryen(target, asm_target, options, memfile, wasm_binary_target,
-                    wasm_text_target, misc_temp_files, optimizer)
+                    wasm_text_target, wasm_source_map_target, misc_temp_files,
+                    optimizer)
 
       if shared.Settings.MODULARIZE:
         modularize()
@@ -2593,7 +2595,8 @@ def separate_asm_js(final, asm_target):
 
 
 def do_binaryen(target, asm_target, options, memfile, wasm_binary_target,
-                wasm_text_target, misc_temp_files, optimizer):
+                wasm_text_target, wasm_source_map_target, misc_temp_files,
+                optimizer):
   global final
   logger.debug('using binaryen')
   binaryen_bin = shared.Building.get_binaryen_bin()
@@ -2657,7 +2660,7 @@ def do_binaryen(target, asm_target, options, memfile, wasm_binary_target,
       if debug_info:
         cmd += ['-g']
         if use_source_map(options):
-          cmd += ['--source-map=' + wasm_binary_target + '.map']
+          cmd += ['--source-map=' + wasm_source_map_target]
           cmd += ['--source-map-url=' + options.source_map_base + os.path.basename(wasm_binary_target) + '.map']
       logger.debug('wasm-as (text => binary): ' + ' '.join(cmd))
       shared.check_call(cmd)
@@ -2677,6 +2680,12 @@ def do_binaryen(target, asm_target, options, memfile, wasm_binary_target,
     cmd += shared.Building.get_binaryen_feature_flags()
     if debug_info:
       cmd += ['-g'] # preserve the debug info
+    if use_source_map(options):
+      cmd += ['--input-source-map=' + wasm_source_map_target]
+      cmd += ['--output-source-map=' + wasm_source_map_target]
+      cmd += ['--output-source-map-url=' + options.source_map_base + os.path.basename(wasm_binary_target) + '.map']
+      if DEBUG:
+        shared.safe_copy(wasm_source_map_target, os.path.join(shared.get_emscripten_temp_dir(), os.path.basename(wasm_source_map_target) + '.pre-byn'))
     logger.debug('wasm-opt on BINARYEN_PASSES: ' + ' '.join(cmd))
     shared.check_call(cmd)
   if shared.Settings.BINARYEN_SCRIPTS: