[PECOFF] Support =internalName syntax in .def file.

Export definitions in a module definition file is as follows:

  exportedname[=internalname] [@ordinal [NONAME]] [PRIVATE] [DATA]

Previously we did not support =internalname, so users couldn't export
symbols from a DLL with a different name.

llvm-svn: 207827

lld/include/lld/ReaderWriter/PECOFFLinkingContext.h

@@ -67,7 +67,7 @@ public:
     }
 
     std::string name;
-    std::string internalName;
+    std::string externalName;
     int ordinal;
     bool noname;
     bool isData;

lld/lib/Driver/WinLinkModuleDef.cpp

@@ -195,6 +195,17 @@ bool Parser::parseExport(PECOFFLinkingContext::ExportDesc &result) {
   }
   result.name = _tok._range;
 
+  consumeToken();
+  if (_tok._kind == Kind::equal) {
+    consumeToken();
+    if (_tok._kind != Kind::identifier)
+      return false;
+    result.externalName = result.name;
+    result.name = _tok._range;
+  } else {
+    ungetToken();
+  }
+
   for (;;) {
     consumeToken();
     if (_tok._kind == Kind::identifier && _tok._range[0] == '@') {

lld/lib/ReaderWriter/PECOFF/EdataPass.cpp

@@ -77,7 +77,8 @@ static bool getExportedAtoms(PECOFFLinkingContext &ctx, MutableFile *file,
     }
     const DefinedAtom *atom = it->second;
     ret.push_back(TableEntry(desc.name, desc.ordinal, atom, desc.noname));
-    desc.internalName = removeLeadingUnderscore(atom->name());
+    if (desc.externalName.empty())
+      desc.externalName = removeLeadingUnderscore(atom->name());
     exports.insert(desc);
   }
   ctx.getDllExports().swap(exports);

lld/lib/ReaderWriter/PECOFF/WriterImportLibrary.cpp

@@ -30,7 +30,7 @@ createModuleDefinitionFile(const PECOFFLinkingContext &ctx) {
      << "EXPORTS\n";
 
   for (const PECOFFLinkingContext::ExportDesc &desc : ctx.getDllExports()) {
-    os << "  " << desc.internalName << " @" << desc.ordinal;
+    os << "  " << desc.externalName << " @" << desc.ordinal;
     if (desc.noname)
       os << " NONAME";
     if (desc.isData)

lld/test/pecoff/Inputs/export.obj.yaml

@@ -48,4 +48,10 @@ symbols:
     SimpleType:      IMAGE_SYM_TYPE_NULL
     ComplexType:     IMAGE_SYM_DTYPE_NULL
     StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            _exportfn6
+    Value:           16
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
 ...

lld/test/pecoff/Inputs/exports.def

@@ -3,3 +3,4 @@
 EXPORTS
   exportfn1 @5   ; foo
   exportfn2
+  exportfn5=exportfn6

lld/test/pecoff/export.test

@@ -39,4 +39,5 @@ CHECK4:      DLL name: export.test.tmp4.dll
 CHECK4:       Ordinal      RVA  Name
 CHECK4-NEXT:        5   0x2008  exportfn1
 CHECK4-NEXT:        6   0x2010  exportfn2
-CHECK4-NEXT:        7   0x2010  exportfn3@256
+CHECK4-NEXT:        7   0x2010  exportfn6
+CHECK4-NEXT:        8   0x2010  exportfn3@256