7 files changed, 49 insertions, 28 deletions
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 9e07ad533f1..dde928ff914 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -592,7 +592,7 @@ public:
   /// WeakUndeclaredIdentifiers - Identifiers contained in
   /// \#pragma weak before declared. rare. may alias another
   /// identifier, declared or undeclared
-  llvm::DenseMap<IdentifierInfo*,WeakInfo> WeakUndeclaredIdentifiers;
+  llvm::MapVector<IdentifierInfo *, WeakInfo> WeakUndeclaredIdentifiers;
 
   /// ExtnameUndeclaredIdentifiers - Identifiers contained in
   /// \#pragma redefine_extname before declared.  Used in Solaris system headers
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index a1a9b9d0b8c..6825dfa41fa 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -524,14 +524,8 @@ void Sema::LoadExternalWeakUndeclaredIdentifiers() {
 
   SmallVector<std::pair<IdentifierInfo *, WeakInfo>, 4> WeakIDs;
   ExternalSource->ReadWeakUndeclaredIdentifiers(WeakIDs);
-  for (unsigned I = 0, N = WeakIDs.size(); I != N; ++I) {
-    llvm::DenseMap<IdentifierInfo*,WeakInfo>::iterator Pos
-      = WeakUndeclaredIdentifiers.find(WeakIDs[I].first);
-    if (Pos != WeakUndeclaredIdentifiers.end())
-      continue;
-
-    WeakUndeclaredIdentifiers.insert(WeakIDs[I]);
-  }
+  for (auto &WeakID : WeakIDs)
+    WeakUndeclaredIdentifiers.insert(WeakID);
 }
 
 
@@ -694,16 +688,13 @@ void Sema::ActOnEndOfTranslationUnit() {
   }
 
   // Check for #pragma weak identifiers that were never declared
-  // FIXME: This will cause diagnostics to be emitted in a non-determinstic
-  // order!  Iterating over a densemap like this is bad.
   LoadExternalWeakUndeclaredIdentifiers();
-  for (llvm::DenseMap<IdentifierInfo*,WeakInfo>::iterator
-       I = WeakUndeclaredIdentifiers.begin(),
-       E = WeakUndeclaredIdentifiers.end(); I != E; ++I) {
-    if (I->second.getUsed()) continue;
+  for (auto WeakID : WeakUndeclaredIdentifiers) {
+    if (WeakID.second.getUsed())
+      continue;
 
-    Diag(I->second.getLocation(), diag::warn_weak_identifier_undeclared)
-      << I->first;
+    Diag(WeakID.second.getLocation(), diag::warn_weak_identifier_undeclared)
+        << WeakID.first;
   }
 
   if (LangOpts.CPlusPlus11 &&
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 336d222f17e..4ef62b9bb5d 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5019,8 +5019,7 @@ void Sema::ProcessPragmaWeak(Scope *S, Decl *D) {
         ND = FD;
     if (ND) {
       if (IdentifierInfo *Id = ND->getIdentifier()) {
-        llvm::DenseMap<IdentifierInfo*,WeakInfo>::iterator I
-          = WeakUndeclaredIdentifiers.find(Id);
+        auto I = WeakUndeclaredIdentifiers.find(Id);
         if (I != WeakUndeclaredIdentifiers.end()) {
           WeakInfo W = I->second;
           DeclApplyPragmaWeak(S, ND, W);
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 9f0626f060c..7227a97e7b9 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4359,15 +4359,13 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
   // entire table, since later PCH files in a PCH chain are only interested in
   // the results at the end of the chain.
   RecordData WeakUndeclaredIdentifiers;
-  if (!SemaRef.WeakUndeclaredIdentifiers.empty()) {
-    for (llvm::DenseMap<IdentifierInfo*,WeakInfo>::iterator
-         I = SemaRef.WeakUndeclaredIdentifiers.begin(),
-         E = SemaRef.WeakUndeclaredIdentifiers.end(); I != E; ++I) {
-      AddIdentifierRef(I->first, WeakUndeclaredIdentifiers);
-      AddIdentifierRef(I->second.getAlias(), WeakUndeclaredIdentifiers);
-      AddSourceLocation(I->second.getLocation(), WeakUndeclaredIdentifiers);
-      WeakUndeclaredIdentifiers.push_back(I->second.getUsed());
-    }
+  for (auto &WeakUndeclaredIdentifier : SemaRef.WeakUndeclaredIdentifiers) {
+    IdentifierInfo *II = WeakUndeclaredIdentifier.first;
+    WeakInfo &WI = WeakUndeclaredIdentifier.second;
+    AddIdentifierRef(II, WeakUndeclaredIdentifiers);
+    AddIdentifierRef(WI.getAlias(), WeakUndeclaredIdentifiers);
+    AddSourceLocation(WI.getLocation(), WeakUndeclaredIdentifiers);
+    WeakUndeclaredIdentifiers.push_back(WI.getUsed());
   }
 
   // Build a record containing all of the ext_vector declarations.
diff --git a/clang/test/Modules/Inputs/stress1/common.h b/clang/test/Modules/Inputs/stress1/common.h
index d2fff1098d9..b158a8e6c1e 100644
--- a/clang/test/Modules/Inputs/stress1/common.h
+++ b/clang/test/Modules/Inputs/stress1/common.h
@@ -35,4 +35,18 @@ struct S01 {};
 struct S02 {};
 }
 
+#pragma weak pragma_weak00
+#pragma weak pragma_weak01
+#pragma weak pragma_weak02
+#pragma weak pragma_weak03
+#pragma weak pragma_weak04
+#pragma weak pragma_weak05
+
+extern "C" int pragma_weak00();
+extern "C" int pragma_weak01();
+extern "C" int pragma_weak02();
+extern "C" int pragma_weak03;
+extern "C" int pragma_weak04;
+extern "C" int pragma_weak05;
+
 #endif
diff --git a/clang/test/Modules/Inputs/stress1/merge00.h b/clang/test/Modules/Inputs/stress1/merge00.h
index c6dccdf5305..b769b0877dd 100644
--- a/clang/test/Modules/Inputs/stress1/merge00.h
+++ b/clang/test/Modules/Inputs/stress1/merge00.h
@@ -1,6 +1,14 @@
 #ifndef STRESS1_MERGE00_H
 #define STRESS1_MERGE00_H
 
+// These don't match the imported declarations because we import them from
+// modules which are built in isolation of the current header's pragma state
+// much like they are built in isolation of the incoming macro state.
+// FIXME: We should expect warnings here but we can't because verify doesn't
+// work for modules.
+//#pragma weak pragma_weak01 // expected-warning {{weak identifier 'pragma_weak01' never declared}}
+//#pragma weak pragma_weak04 // expected-warning {{weak identifier 'pragma_waek04' never declared}}
+
 #include "m00.h"
 #include "m01.h"
 #include "m02.h"
@@ -8,4 +16,10 @@
 
 inline int g() { return N00::S00('a').method00('b') + (int)N00::S00(42) + function00(42); }
 
+#pragma weak pragma_weak02
+#pragma weak pragma_weak05
+
+extern "C" int pragma_weak02();
+int pragma_weak05;
+
 #endif
diff --git a/clang/test/Modules/stress1.cpp b/clang/test/Modules/stress1.cpp
index 55d9533b7ae..e03e538a3ce 100644
--- a/clang/test/Modules/stress1.cpp
+++ b/clang/test/Modules/stress1.cpp
@@ -98,3 +98,8 @@
 #include "merge00.h"
 
 int f() { return N01::S00('a').method00('b') + (int)N00::S00(42) + function00(42) + g(); }
+
+int f2() {
+  return pragma_weak00() + pragma_weak01() + pragma_weak02() +
+         pragma_weak03 + pragma_weak04 + pragma_weak05;
+}