Don't dump full debug info section when creating source maps (#9580)

wasm-sourcemap.py dumps the entire .debug_info section when creating source maps (which really only contains the info from the .debug_line section). It does this because it wants to find the compilation directory (DW_AT_comp_dir) associated with each compile unit, and remove it from the path of each file in the debug line section. However dumping the entire debug info section is very slow for large wasm files, and is unnecessary. Instead, only dump the top-level entities (the DW_TAG_compile_unit and don't recurse into their children).

This goes a long way toward fixing #8948.

Author: dschuff

tools/wasm-sourcemap.py

@@ -178,7 +178,7 @@ def read_dwarf_entries(wasm, options):
     if not os.path.exists(options.dwarfdump):
       logger.error('llvm-dwarfdump not found: ' + options.dwarfdump)
       sys.exit(1)
-    process = Popen([options.dwarfdump, "-debug-info", "-debug-line", wasm], stdout=PIPE)
+    process = Popen([options.dwarfdump, '-debug-info', '-debug-line', '--recurse-depth=0', wasm], stdout=PIPE)
     output, err = process.communicate()
     exit_code = process.wait()
     if exit_code != 0: