[llvm-dlltool] Make sure to strip decorations from ExtName for renamed exports

ExtName should not be decorated, just like Name.

This avoids double decoration on symbols in import libraries
that use = for renaming functions. (Weak aliases, which use ==,
worked fine with respect to decoration.)

Differential Revision: https://reviews.llvm.org/D66617

llvm-svn: 369747

lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp

@@ -171,6 +171,7 @@ int llvm::dlltoolDriverMain(llvm::ArrayRef<const char *> ArgsArr) {
       // By making sure E.SymbolName != E.Name for decorated symbols,
       // writeImportLibrary writes these symbols with the type
       // IMPORT_NAME_UNDECORATE.
+      E.ExtName = E.ExtName.substr(0, E.ExtName.find('@', 1));
     }
   }
 

test/tools/llvm-dlltool/coff-decorated.def

@@ -9,6 +9,7 @@ StdcallFunction@4
 @FastcallFunction@4
 StdcallAlias@4==StdcallFunction@4
 ??_7exception@@6B@
+StdcallExportName@4=StdcallInternalFunction@4
 
 ; CHECK: Name type: noprefix
 ; CHECK: Symbol: __imp__CdeclFunction
@@ -24,3 +25,5 @@ StdcallAlias@4==StdcallFunction@4
 ; CHECK: Symbol: ??_7exception@@6B@
 ; CHECK-NM: W _StdcallAlias@4
 ; CHECK-NM: U _StdcallFunction@4
+; CHECK: Symbol: __imp__StdcallExportName@4{{$}}
+; CHECK: Symbol: _StdcallExportName@4{{$}}