[ms] [llvm-ml] Use cleaner COFF symbol handling

[epastor]

Summary

Rather than directly controlling the streamer, use MCSymbolCOFF's interface for type, etc.

[rnk]

lgtm

[epastor]

Incorporated into D87403.

llvm/lib/MC/MCParser/COFFMasmParser.cpp

 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/MC/MCParser/MCAsmParserUtils.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbolCOFF.h"
 #include "llvm/MC/SectionKind.h"
 #include "llvm/Support/SMLoc.h"
 #include <cassert>
 #include <cstdint>
 #include <limits>
 #include <utility>
 
 using namespace llvm;
if (nextVal.equals_lower("far")) {
       Lex();
       return Error(nextLoc, "far procedure definitions not yet supported");
     } else if (nextVal.equals_lower("near")) {
       Lex();
       nextVal = getTok().getString();
       nextLoc = getTok().getLoc();
     }
   }
-  MCSymbol *Sym = getContext().getOrCreateSymbol(Label);
+  MCSymbolCOFF *Sym = cast<MCSymbolCOFF>(getContext().getOrCreateSymbol(Label));
 
-  // Define symbol as simple function
-  getStreamer().BeginCOFFSymbolDef(Sym);
-  getStreamer().EmitCOFFSymbolStorageClass(2);
-  getStreamer().EmitCOFFSymbolType(0x20);
-  getStreamer().EndCOFFSymbolDef();
+  // Define symbol as simple external function
+  Sym->setExternal(true);
+  Sym->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION << COFF::SCT_COMPLEX_TYPE_SHIFT);
 
   bool Framed = false;
   if (getLexer().is(AsmToken::Identifier) &&
       getTok().getString().equals_lower("frame")) {
     Lex();
     Framed = true;
     getStreamer().EmitWinCFIStartProc(Sym, Loc);
   }

llvm/lib/MC/MCWinCOFFStreamer.cpp

void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
   Symbol->setExternal(false);
   emitZeros(Size);
   PopSection();
 }
 
 void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
                                           const MCSymbol *Symbol) {
   auto *Alias = cast<MCSymbolCOFF>(AliasS);
-  Alias->setIsWeakExternal();
+  emitSymbolAttribute(Alias, MCSA_Weak);
 
-  BeginCOFFSymbolDef(AliasS);
-  EmitCOFFSymbolStorageClass(
-      COFF::SymbolStorageClass::IMAGE_SYM_CLASS_WEAK_EXTERNAL);
-  EmitCOFFSymbolType(COFF::SymbolBaseType::IMAGE_SYM_TYPE_NULL);
-  EndCOFFSymbolDef();
+  getAssembler().registerSymbol(*Symbol);
+  Alias->setVariableValue(MCSymbolRefExpr::create(
+      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
 }
 
 void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
                                      uint64_t Size, unsigned ByteAlignment,
                                      SMLoc Loc) {
   llvm_unreachable("not implemented");
 }