Add debug option to wasm-ld to enable LLVM style debug info

[pmatos]

Summary

Adds -debug flag to wasm-ld to enable LLVM debug information.
Also adds test.

[sbc100]

This is already supported like via -mllvm. E.g. wasm-ld -mllvm -debug or wasm-ld -mllvm -debug-only=lld

[pmatos]

In D88226#2292764, @sbc100 wrote:

This is already supported like via -mllvm. E.g. wasm-ld -mllvm -debug or wasm-ld -mllvm -debug-only=lld

Argh - I completely forgot that was possible from wasm-ld. Abandoning revision. Apologies for the noise.

lld/test/wasm/debug.test

+RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/start.s -o %t.foo.o
+
+# Check -debug
+RUN: wasm-ld %t.foo.o -o %t.t.out.wasm -debug 2>&1 | FileCheck %s
+CHECK: Args: wasm-ld (LLVM option parsing)
+CHECK: wasm-ld: writing MEMORY
+

lld/wasm/Driver.cpp

static void wrapSymbols(ArrayRef<WrappedSymbol> wrapped) {
   for (const WrappedSymbol &w : wrapped)
     symtab->wrap(w.sym, w.real, w.wrap);
 }
 
 void LinkerDriver::link(ArrayRef<const char *> argsArr) {
   WasmOptTable parser;
   opt::InputArgList args = parser.parse(argsArr.slice(1));
 
+  // Handle -debug
+  if (args.hasArg(OPT_debug))
+    DebugFlag = true;
+
   // Handle --help
   if (args.hasArg(OPT_help)) {
     parser.PrintHelp(lld::outs(),
                      (std::string(argsArr[0]) + " [options] file...").c_str(),
                      "LLVM Linker", false);
     return;
   }
 

lld/wasm/Options.td

def import_table: F<"import-table">,
   HelpText<"Import function table from the environment">;
 
 def initial_memory: J<"initial-memory=">,
   HelpText<"Initial size of the linear memory">;
 
 def max_memory: J<"max-memory=">,
   HelpText<"Maximum size of the linear memory">;
 
+def debug: F<"debug">,
+  HelpText<"Enable LLVM style debug output">;
+
 def no_entry: F<"no-entry">,
   HelpText<"Do not output any entry point">;
 
 def stack_first: F<"stack-first">,
   HelpText<"Place stack at start of linear memory rather than after data">;
 
 defm whole_archive: B<"whole-archive",
     "Force load of all members in a static library",