From c52efa7d4011a48ea91b353f2cbc40a359d19571 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Wed, 19 Aug 2015 02:30:28 +0000
Subject: [PATCH] [modules] Don't eagerly deserialize so many ImportDecls.
 CodeGen basically ignores ImportDecls imported from modules, so only eagerly
 deserialize the ones from a PCH / preamble.

llvm-svn: 245406
---
 clang/lib/CodeGen/CodeGenModule.cpp       |  7 ++-----
 clang/lib/Serialization/ASTWriterDecl.cpp | 17 +++++++++++------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 76e6f3dcde41..6352646f19c5 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3363,11 +3363,8 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     auto *Import = cast<ImportDecl>(D);
 
     // Ignore import declarations that come from imported modules.
-    if (clang::Module *Owner = Import->getImportedOwningModule()) {
-      if (getLangOpts().CurrentModule.empty() ||
-          Owner->getTopLevelModule()->Name == getLangOpts().CurrentModule)
-        break;
-    }
+    if (Import->getImportedOwningModule())
+      break;
     if (CGDebugInfo *DI = getModuleDebugInfo())
       DI->EmitImportDecl(*Import);
 
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index fd6708dd5c3f..02e1a4b0b9f3 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1994,14 +1994,19 @@ void ASTWriter::WriteDeclAbbrevs() {
 /// clients to use a separate API call to "realize" the decl. This should be
 /// relatively painless since they would presumably only do it for top-level
 /// decls.
-static bool isRequiredDecl(const Decl *D, ASTContext &Context) {
+static bool isRequiredDecl(const Decl *D, ASTContext &Context,
+                           bool WritingModule) {
   // An ObjCMethodDecl is never considered as "required" because its
   // implementation container always is.
 
-  // File scoped assembly or obj-c implementation must be seen. ImportDecl is
-  // used by codegen to determine the set of imported modules to search for
-  // inputs for automatic linking.
-  if (isa<FileScopeAsmDecl>(D) || isa<ObjCImplDecl>(D) || isa<ImportDecl>(D))
+  // File scoped assembly or obj-c implementation must be seen.
+  if (isa<FileScopeAsmDecl>(D) || isa<ObjCImplDecl>(D))
+    return true;
+
+  // ImportDecl is used by codegen to determine the set of imported modules to
+  // search for inputs for automatic linking; include it if it has a semantic
+  // effect.
+  if (isa<ImportDecl>(D) && !WritingModule)
     return true;
 
   return Context.DeclMustBeEmitted(D);
@@ -2090,7 +2095,7 @@ void ASTWriter::WriteDecl(ASTContext &Context, Decl *D) {
 
   // Note declarations that should be deserialized eagerly so that we can add
   // them to a record in the AST file later.
-  if (isRequiredDecl(D, Context))
+  if (isRequiredDecl(D, Context, WritingModule))
     EagerlyDeserializedDecls.push_back(ID);
 }