llvm: add llvm-dlltool support to the archiver

A PE COFF spec compliant import library generator.
Intended to be used with mingw-w64.

Supports:
PE COFF spec (section 8, Import Library Format)
PE COFF spec (Aux Format 3: Weak Externals)

Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D29892

This reapplies rL308329, which was reverted in rL308374

llvm-svn: 308379

llvm/lib/Object/COFFModuleDefinition.cpp

@@ -55,8 +55,10 @@ struct Token {
   StringRef Value;
 };
 
-static bool isDecorated(StringRef Sym) {
-  return Sym.startswith("_") || Sym.startswith("@") || Sym.startswith("?");
+static bool isDecorated(StringRef Sym, bool MingwDef) {
+  // mingw does not prepend "_".
+  return (!MingwDef && Sym.startswith("_")) || Sym.startswith("@") ||
+         Sym.startswith("?");
 }
 
 static Error createError(const Twine &Err) {
@@ -83,6 +85,9 @@ public:
     }
     case '=':
       Buf = Buf.drop_front();
+      // GNU dlltool accepts both = and ==.
+      if (Buf.startswith("="))
+        Buf = Buf.drop_front();
       return Token(Equal, "=");
     case ',':
       Buf = Buf.drop_front();
@@ -120,7 +125,8 @@ private:
 
 class Parser {
 public:
-  explicit Parser(StringRef S, MachineTypes M) : Lex(S), Machine(M) {}
+  explicit Parser(StringRef S, MachineTypes M, bool B)
+      : Lex(S), Machine(M), MingwDef(B) {}
 
   Expected<COFFModuleDefinition> parse() {
     do {
@@ -213,9 +219,9 @@ private:
     }
 
     if (Machine == IMAGE_FILE_MACHINE_I386) {
-      if (!isDecorated(E.Name))
+      if (!isDecorated(E.Name, MingwDef))
         E.Name = (std::string("_").append(E.Name));
-      if (!E.ExtName.empty() && !isDecorated(E.ExtName))
+      if (!E.ExtName.empty() && !isDecorated(E.ExtName, MingwDef))
         E.ExtName = (std::string("_").append(E.ExtName));
     }
 
@@ -308,11 +314,13 @@ private:
   std::vector<Token> Stack;
   MachineTypes Machine;
   COFFModuleDefinition Info;
+  bool MingwDef;
 };
 
 Expected<COFFModuleDefinition> parseCOFFModuleDefinition(MemoryBufferRef MB,
-                                                         MachineTypes Machine) {
-  return Parser(MB.getBuffer(), Machine).parse();
+                                                         MachineTypes Machine,
+                                                         bool MingwDef) {
+  return Parser(MB.getBuffer(), Machine, MingwDef).parse();
 }
 
 } // namespace object