[clang] serialize SUBMODULE_TOPHEADER relative to BaseDirectory

[rmaz]

Summary

This diff changes the serialization of the SUBMODULE_TOPHEADER
entry in module files to be serialized relative to the module's
BaseDirectory. This matches the behavior of the
SUBMODULE_HEADER entry and will allow for the module to be
relocatable across machines.

The path is restored relative to the module's BaseDirectory on
deserialization.

[urnathan]

lgtm

clang/lib/Serialization/ASTReader.cpp

case SUBMODULE_PRIVATE_HEADER:
       break;
 
     case SUBMODULE_TEXTUAL_HEADER:
     case SUBMODULE_PRIVATE_TEXTUAL_HEADER:
       // FIXME: Textual headers are not marked in the HeaderInfo table. Load
       // them here.
       break;
 
-    case SUBMODULE_TOPHEADER:
-      CurrentModule->addTopHeaderFilename(Blob);
+    case SUBMODULE_TOPHEADER: {
+      std::string HeaderName(Blob);
+      ResolveImportedPath(F, HeaderName);
+      CurrentModule->addTopHeaderFilename(HeaderName);
       break;
+    }
 
     case SUBMODULE_UMBRELLA_DIR: {
       // See comments in SUBMODULE_UMBRELLA_HEADER
       std::string Dirname = std::string(Blob);
       ResolveImportedPath(F, Dirname);
       if (auto Umbrella = PP.getFileManager().getDirectory(Dirname)) {
         if (!CurrentModule->getUmbrellaDir()) {
           // FIXME: NameAsWritten

clang/lib/Serialization/ASTWriter.cpp

for (auto &HL : HeaderLists) {
       for (auto &H : Mod->Headers[HL.HeaderKind])
         Stream.EmitRecordWithBlob(HL.Abbrev, Record, H.NameAsWritten);
     }
 
     // Emit the top headers.
     {
       auto TopHeaders = Mod->getTopHeaders(PP->getFileManager());
       RecordData::value_type Record[] = {SUBMODULE_TOPHEADER};
-      for (auto *H : TopHeaders)
-        Stream.EmitRecordWithBlob(TopHeaderAbbrev, Record, H->getName());
+      for (auto *H : TopHeaders) {
+        SmallString<128> HeaderName(H->getName());
+        PreparePathForOutput(HeaderName);
+        Stream.EmitRecordWithBlob(TopHeaderAbbrev, Record, HeaderName);
+      }
     }
 
     // Emit the imports.
     if (!Mod->Imports.empty()) {
       RecordData Record;
       for (auto *I : Mod->Imports)
         Record.push_back(getSubmoduleID(I));
       Stream.EmitRecord(SUBMODULE_IMPORTS, Record);

clang/test/Modules/relative-submodule-topheader.m

+// RUN: cd %S
+// RUN: %clang_cc1 -fmodules -fno-implicit-modules -x objective-c++ -fmodule-name=std -emit-module Inputs/submodules/module.map -o %t/mod.pcm
+// RUN: llvm-bcanalyzer --dump --disable-histogram %t/mod.pcm | FileCheck %s
+
+// CHECK: <SUBMODULE_HEADER abbrevid=6/> blob data = 'vector.h'
+// CHECK: <SUBMODULE_TOPHEADER abbrevid=7/> blob data = 'vector.h'
+// CHECK: <SUBMODULE_HEADER abbrevid=6/> blob data = 'type_traits.h'
+// CHECK: <SUBMODULE_TOPHEADER abbrevid=7/> blob data = 'type_traits.h'
+// CHECK: <SUBMODULE_HEADER abbrevid=6/> blob data = 'hash_map.h'
+// CHECK: <SUBMODULE_TOPHEADER abbrevid=7/> blob data = 'hash_map.h'