[Module map] Introduce a private module re-export directive.

Introduce a new "export_as" directive for top-level modules, which
indicates that the current module is a "private" module whose symbols
will eventually be exported through the named "public" module. This is
in support of a common pattern in the Darwin ecosystem where a single
public framework is constructed of several private frameworks, with
(currently) header duplication and some support from the linker.

Addresses rdar://problem/34438420.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313316 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 3dba299790..46823030d3 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -5123,7 +5123,7 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
     }
 
-    case SUBMODULE_INITIALIZERS:
+    case SUBMODULE_INITIALIZERS: {
       if (!ContextObj)
         break;
       SmallVector<uint32_t, 16> Inits;
@@ -5132,6 +5132,11 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       ContextObj->addLazyModuleInitializers(CurrentModule, Inits);
       break;
     }
+
+    case SUBMODULE_EXPORT_AS:
+      CurrentModule->ExportAsModule = Blob.str();
+      break;
+    }
   }
 }