COFF: actually synthesize CONST imports properly

CONSTANT imports expect both the `_imp_` prefixed and non-prefixed
symbols should be added to the symbol table.  This allows for linking
symbols like _NSConcreteGlobalBlock in WinObjC.  The previous change
would generate the import library properly by handling the option but
would not consume the generated entry properly.

llvm-svn: 301657

lld/COFF/InputFiles.cpp

@@ -327,6 +327,9 @@ void ImportFile::parse() {
 
   ImpSym = cast<DefinedImportData>(
       Symtab->addImportData(ImpName, this)->body());
+  if (Hdr->getType() == llvm::COFF::IMPORT_CONST)
+    ConstSym =
+        cast<DefinedImportData>(Symtab->addImportData(Name, this)->body());
 
   // If type is function, we need to create a thunk which jump to an
   // address pointed by the __imp_ symbol. (This allows you to call

lld/COFF/InputFiles.h

@@ -167,6 +167,7 @@ public:
   static bool classof(const InputFile *F) { return F->kind() == ImportKind; }
 
   DefinedImportData *ImpSym = nullptr;
+  DefinedImportData *ConstSym = nullptr;
   DefinedImportThunk *ThunkSym = nullptr;
   std::string DLLName;
 

lld/test/COFF/Inputs/constant-import.s

@@ -0,0 +1,21 @@
+
+	.def __DllMainCRTStartup@12
+		.type 32
+		.scl 2
+	.endef
+	.global __DllMainCRTStartup@12
+__DllMainCRTStartup@12:
+	ret
+
+	.data
+	.def _Data
+		.type 0
+		.scl 2
+	.endef
+	.global _Data
+_Data:
+	.long ___CFConstantStringClassReference
+
+	.section .drectve
+	.ascii " -export:_Data"
+

lld/test/COFF/constant.test

@@ -0,0 +1,5 @@
+RUN: mkdir -p %t
+RUN: llvm-mc -triple i686-unknown-windows-msvc -filetype obj -o %t/import.o %S/Inputs/constant-import.s
+RUN: llc -mtriple i686-unknown-windows-msvc -filetype obj -o %t/export.o %S/Inputs/constant-export.ll
+RUN: lld-link -machine:x86 -dll -out:%t/export.dll %t/export.o -entry:__CFConstantStringClassReference
+RUN: lld-link -machine:x86 -dll -out:%t/import.dll %t/import.o %t/export.lib