From 4b3e7388d1a90f3e20a90d5624fe54dccca2610f Mon Sep 17 00:00:00 2001
From: Vassil Vassilev <v.g.vassilev@gmail.com>
Date: Tue, 11 Oct 2016 13:57:36 +0000
Subject: [modules] PR28752: Do not instantiate variable declarations which are
 not visible.

https://reviews.llvm.org/D24508

Patch developed in collaboration with Richard Smith!

llvm-svn: 283882
---
 clang/lib/Serialization/ASTReaderDecl.cpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'clang/lib/Serialization/ASTReaderDecl.cpp')

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 19113da7e3c..864eaf02b02 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1216,6 +1216,7 @@ ASTDeclReader::RedeclarableResult ASTDeclReader::VisitVarDeclImpl(VarDecl *VD) {
   VD->VarDeclBits.TSCSpec = Record[Idx++];
   VD->VarDeclBits.InitStyle = Record[Idx++];
   if (!isa<ParmVarDecl>(VD)) {
+    VD->NonParmVarDeclBits.IsThisDeclarationADemotedDefinition = Record[Idx++];
     VD->NonParmVarDeclBits.ExceptionVar = Record[Idx++];
     VD->NonParmVarDeclBits.NRVOVariable = Record[Idx++];
     VD->NonParmVarDeclBits.CXXForRangeDecl = Record[Idx++];
@@ -3067,6 +3068,34 @@ void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
 }
 
 namespace clang {
+template<>
+void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
+                                           Redeclarable<VarDecl> *D,
+                                           Decl *Previous, Decl *Canon) {
+  VarDecl *VD = static_cast<VarDecl*>(D);
+  VarDecl *PrevVD = cast<VarDecl>(Previous);
+  D->RedeclLink.setPrevious(PrevVD);
+  D->First = PrevVD->First;
+
+
+  // We should keep at most one definition on the chain.
+  if (VD->isThisDeclarationADefinition()) {
+    for (VarDecl *CurD = PrevVD; CurD; CurD = CurD->getPreviousDecl()) {
+      // If we find an already demoted definition, this we already visited this
+      // part of the chain. Reduces the loop from quadratic-time to linear-time.
+      if (CurD->isThisDeclarationADemotedDefinition()) {
+        VD->demoteThisDefinitionToDeclaration();
+        break;
+      }
+      if (CurD->isThisDeclarationADefinition()) {
+        // If we found another definition on the chain, demote the current one.
+        VD->demoteThisDefinitionToDeclaration();
+        break;
+      }
+    }
+  }
+}
+
 template<>
 void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
                                            Redeclarable<FunctionDecl> *D,
-- 
cgit v1.2.3