make -fmodules-codegen and -fmodules-debuginfo work also with PCHs

Allow to build PCH's (with -building-pch-with-obj and the extra .o file)
with -fmodules-codegen -fmodules-debuginfo to allow emitting shared code
into the extra .o file, similarly to how it works with modules. A bit of
a misnomer, but the underlying functionality is the same. This saves up
to 20% of build time here.

Differential Revision: https://reviews.llvm.org/D69778

6 files changed, 60 insertions, 11 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index a9f433b5007..6c8bc7dc33a 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3224,7 +3224,8 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
     case MODULAR_CODEGEN_DECLS:
       // FIXME: Skip reading this record if our ASTConsumer doesn't care about
       // them (ie: if we're not codegenerating this module).
-      if (F.Kind == MK_MainFile)
+      if (F.Kind == MK_MainFile ||
+          getContext().getLangOpts().BuildingPCHWithObjectFile)
         for (unsigned I = 0, N = Record.size(); I != N; ++I)
           EagerlyDeserializedDecls.push_back(getGlobalDeclID(F, Record[I]));
       break;
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index a132164d30e..3bcc9ad5805 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -501,8 +501,12 @@ uint64_t ASTDeclReader::GetCurrentCursorOffset() {
 }
 
 void ASTDeclReader::ReadFunctionDefinition(FunctionDecl *FD) {
-  if (Record.readInt())
+  if (Record.readInt()) {
     Reader.DefinitionSource[FD] = Loc.F->Kind == ModuleKind::MK_MainFile;
+    if (Reader.getContext().getLangOpts().BuildingPCHWithObjectFile &&
+        Reader.DeclIsFromPCHWithObjectFile(FD))
+      Reader.DefinitionSource[FD] = true;
+  }
   if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
     CD->setNumCtorInitializers(Record.readInt());
     if (CD->getNumCtorInitializers())
@@ -1417,8 +1421,12 @@ ASTDeclReader::RedeclarableResult ASTDeclReader::VisitVarDeclImpl(VarDecl *VD) {
       Reader.getContext().setBlockVarCopyInit(VD, CopyExpr, Record.readInt());
   }
 
-  if (VD->getStorageDuration() == SD_Static && Record.readInt())
+  if (VD->getStorageDuration() == SD_Static && Record.readInt()) {
     Reader.DefinitionSource[VD] = Loc.F->Kind == ModuleKind::MK_MainFile;
+    if (Reader.getContext().getLangOpts().BuildingPCHWithObjectFile &&
+        Reader.DeclIsFromPCHWithObjectFile(VD))
+      Reader.DefinitionSource[VD] = true;
+  }
 
   enum VarKind {
     VarNotTemplate = 0, VarTemplate, StaticDataMemberSpecialization
@@ -1677,8 +1685,12 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.ODRHash = Record.readInt();
   Data.HasODRHash = true;
 
-  if (Record.readInt())
+  if (Record.readInt()) {
     Reader.DefinitionSource[D] = Loc.F->Kind == ModuleKind::MK_MainFile;
+    if (Reader.getContext().getLangOpts().BuildingPCHWithObjectFile &&
+        Reader.DeclIsFromPCHWithObjectFile(D))
+      Reader.DefinitionSource[D] = true;
+  }
 
   Data.NumBases = Record.readInt();
   if (Data.NumBases)
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index aebdfa90706..6eba48a1abe 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5583,8 +5583,8 @@ void ASTRecordWriter::AddCXXDefinitionData(const CXXRecordDecl *D) {
 
   // getODRHash will compute the ODRHash if it has not been previously computed.
   Record->push_back(D->getODRHash());
-  bool ModulesDebugInfo = Writer->Context->getLangOpts().ModulesDebugInfo &&
-                          Writer->WritingModule && !D->isDependentType();
+  bool ModulesDebugInfo =
+      Writer->Context->getLangOpts().ModulesDebugInfo && !D->isDependentType();
   Record->push_back(ModulesDebugInfo);
   if (ModulesDebugInfo)
     Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(D));
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 74a49fa813a..6b8a9d9719d 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1010,15 +1010,16 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
 
   if (D->getStorageDuration() == SD_Static) {
     bool ModulesCodegen = false;
-    if (Writer.WritingModule &&
-        !D->getDescribedVarTemplate() && !D->getMemberSpecializationInfo() &&
+    if (!D->getDescribedVarTemplate() && !D->getMemberSpecializationInfo() &&
         !isa<VarTemplateSpecializationDecl>(D)) {
       // When building a C++ Modules TS module interface unit, a strong
       // definition in the module interface is provided by the compilation of
       // that module interface unit, not by its users. (Inline variables are
       // still emitted in module users.)
       ModulesCodegen =
-          (Writer.WritingModule->Kind == Module::ModuleInterfaceUnit &&
+          (((Writer.WritingModule &&
+             Writer.WritingModule->Kind == Module::ModuleInterfaceUnit) ||
+            Writer.Context->getLangOpts().BuildingPCHWithObjectFile) &&
            Writer.Context->GetGVALinkageForVariable(D) == GVA_StrongExternal);
     }
     Record.push_back(ModulesCodegen);
@@ -2425,9 +2426,11 @@ void ASTRecordWriter::AddFunctionDefinition(const FunctionDecl *FD) {
 
   assert(FD->doesThisDeclarationHaveABody());
   bool ModulesCodegen = false;
-  if (Writer->WritingModule && !FD->isDependentContext()) {
+  if (!FD->isDependentContext()) {
     Optional<GVALinkage> Linkage;
-    if (Writer->WritingModule->Kind == Module::ModuleInterfaceUnit) {
+    if ((Writer->WritingModule &&
+         Writer->WritingModule->Kind == Module::ModuleInterfaceUnit) ||
+        Writer->Context->getLangOpts().BuildingPCHWithObjectFile) {
       // When building a C++ Modules TS module interface unit, a strong
       // definition in the module interface is provided by the compilation of
       // that module interface unit, not by its users. (Inline functions are
diff --git a/clang/test/Modules/Inputs/codegen-flags/foo.h b/clang/test/Modules/Inputs/codegen-flags/foo.h
index 7b9c1cd8e08..74cfab1771f 100644
--- a/clang/test/Modules/Inputs/codegen-flags/foo.h
+++ b/clang/test/Modules/Inputs/codegen-flags/foo.h
@@ -1,4 +1,7 @@
+#ifndef FOO_H
+#define FOO_H
 struct foo {
 };
 inline void f1() {
 }
+#endif
diff --git a/clang/test/PCH/codegen.cpp b/clang/test/PCH/codegen.cpp
new file mode 100644
index 00000000000..120db0e82b9
--- /dev/null
+++ b/clang/test/PCH/codegen.cpp
@@ -0,0 +1,30 @@
+// This test is the PCH version of Modules/codegen-flags.test . It uses its inputs.
+// The purpose of this test is just verify that the codegen options work with PCH as well.
+// All the codegen functionality should be tested in Modules/.
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// REQUIRES: x86-registered-target
+
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-codegen -x c++-header -building-pch-with-obj -emit-pch %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-cg.pch
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -fmodules-debuginfo -x c++-header -building-pch-with-obj -emit-pch %S/../Modules/Inputs/codegen-flags/foo.h -o %t/foo-di.pch
+
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-cg.pch -building-pch-with-obj -fmodules-codegen | FileCheck --check-prefix=CG %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - %s -include-pch %t/foo-di.pch -building-pch-with-obj -fmodules-debuginfo | FileCheck --check-prefix=DI %s
+
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-cg.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=CG-USE %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -debug-info-kind=limited -o - -include-pch %t/foo-di.pch %S/../Modules/Inputs/codegen-flags/use.cpp | FileCheck --check-prefix=DI-USE %s
+
+// CG: define weak_odr void @_Z2f1v
+// CG: DICompileUnit
+// CG-NOT: DICompositeType
+
+// CG-USE: declare void @_Z2f1v
+// CG-USE: DICompileUnit
+// CG-USE: distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo"
+
+// DI-NOT: define
+// DI: distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo"
+
+// DI-USE: define linkonce_odr void @_Z2f1v
+// DI-USE: = !DICompositeType(tag: DW_TAG_structure_type, name: "foo", {{.*}}, flags: DIFlagFwdDecl