[lld-macho] Initialize AsmParsers earlier

[int3]

Summary

We need to initialize AsmParsers before any calls to addFile, as
bitcode files may require them. Otherwise we trigger `Assertion T &&
T->hasMCAsmParser()' failed`.

[compnerd]

lld/MachO/Driver.cpp

752

Nit: a newline after this would be nice.

[int3]

newline

lld/MachO/Driver.cpp

if (args.hasArg(OPT_v)) {
     message(StringRef("Framework search paths:") +
             (config->frameworkSearchPaths.size()
                  ? "\n\t" + llvm::join(config->frameworkSearchPaths, "\n\t")
                  : ""));
     freeArena();
     return !errorCount();
   }
 
+  initLLVM(); // must be run before any call to addFile()
+
   for (const auto &arg : args) {
     const auto &opt = arg->getOption();
     warnIfDeprecatedOption(opt);
     warnIfUnimplementedOption(opt);
     // TODO: are any of these better handled via filtered() or getLastArg()?
     switch (opt.getID()) {
     case OPT_INPUT:
       addFile(arg->getValue(), false);
bool macho::link(llvm::ArrayRef<const char *> argsArr, bool canExitEarly,
   // Parse LTO options.
   if (auto *arg = args.getLastArg(OPT_mcpu))
     parseClangOption(saver.save("-mcpu=" + StringRef(arg->getValue())),
                      arg->getSpelling());
 
   for (auto *arg : args.filtered(OPT_mllvm))
     parseClangOption(arg->getValue(), arg->getSpelling());
 
-  initLLVM();
   compileBitcodeFiles();
   replaceCommonSymbols();
 
   StringRef orderFile = args.getLastArgValue(OPT_order_file);
   if (!orderFile.empty())
     parseOrderFile(orderFile);
 
   if (config->outputType == MH_EXECUTE && isa<Undefined>(config->entry)) {

lld/test/MachO/module-asm.ll

+; REQUIRES: x86
+; RUN: llvm-as %s -o %t.o
+; RUN: %lld %t.o -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s
+
+; CHECK:      <_foo>:
+; CHECK-NEXT: retq
+
+; CHECK:      <_main>:
+; CHECK-NEXT: jmp {{.*}} <_foo>
+
+target triple = "x86_64-apple-macosx10.15.0"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+module asm ".text"
+module asm ".globl _foo"
+module asm "_foo: ret"
+
+declare void @foo()
+
+define void @main() {
+  call void @foo()
+  ret void
+}