[lld-link] initialize targets and asmparsers before invoking lib

[inglorion]

Summary

When using lld-link to build static libraries containing object files
with module assembly, the program would crash with "Assertion `T &&
T->hasMCAsmParser()' failed". This change causes the code in lld-link
that initialized Targets, TargetInfos, and AsmParsers (which already
existed) to be run before entering the lib building path (which needs
it). This avoids the error (and is what llvm-lib and llvm-ar do, too).

Fixes PR41803.

[rnk]

Nice.

lld/test/COFF/lib-module-asm.ll

4

Please extend this to put some symbols in the module assembly and then run llvm-nm on the archive to show that the archiver actually parsed the module level assembly and didn't just ignore it. There's a test at llvm/test/Object/X86/archive-ir-asm.ll that does this that you can steal.

[inglorion]

added symbols and check they are listed

[ruiu]

LGTM

lld/COFF/Driver.cpp

Symtab->forEachSymbol([&](Symbol *S) {
     if (Chunk *C = Def->getChunk())
       if (!(C->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
         E.Data = true;
     Config->Exports.push_back(E);
   });
 }
 
 void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
+  // Needed for LTO.
+  InitializeAllTargetInfos();
+  InitializeAllTargets();
+  InitializeAllTargetMCs();
+  InitializeAllAsmParsers();
+  InitializeAllAsmPrinters();
+
   // If the first command line argument is "/lib", link.exe acts like lib.exe.
   // We call our own implementation of lib.exe that understands bitcode files.
   if (ArgsArr.size() > 1 && StringRef(ArgsArr[1]).equals_lower("/lib")) {
     if (llvm::libDriverMain(ArgsArr.slice(1)) != 0)
       fatal("lib failed");
     return;
   }
 
-  // Needed for LTO.
-  InitializeAllTargetInfos();
-  InitializeAllTargets();
-  InitializeAllTargetMCs();
-  InitializeAllAsmParsers();
-  InitializeAllAsmPrinters();
-
   // Parse command line options.
   ArgParser Parser;
   opt::InputArgList Args = Parser.parseLINK(ArgsArr);
 
   // Parse and evaluate -mllvm options.
   std::vector<const char *> V;
   V.push_back("lld-link (LLVM option parsing)");
   for (auto *Arg : Args.filtered(OPT_mllvm))

lld/test/COFF/lib-module-asm.ll

+; PR41803: llvm-link /lib on object with module asm crashes
+; RUN: rm -f %t.lib
+; RUN: llvm-as -o %t.obj %s
+; RUN: lld-link /lib /out:%t.lib %t.obj
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc19.11.0"
+
+module asm ".section .text"