[PATCH] Sema: Propagate the mangling number into instantiations

[David Majnemer]

Hi rsmith, doug.gregor, rjmccall,

We would lose track of the mangling number assigned to the original
declaration which would cause us to create manglings that didn't match
the Itanium C++ specification.

e.g. Two static fields with the same name inside of a function template
would receive the same mangling with LLVM fixing up the second field so
they wouldn't collide.  This would create an incompatibility with other
compilers following the Itanium ABI.

I've confirmed that the new mangling is identical to the ones generated
by icc and gcc.

N.B. This was uncovered while working on Microsoft mangler.

http://llvm-reviews.chandlerc.com/D2203

Files:
  lib/Sema/SemaTemplateInstantiateDecl.cpp
  test/CodeGenCXX/mangle-template.cpp

Index: lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -639,6 +639,8 @@
 
   Enum->setInstantiationOfMemberEnum(D, TSK_ImplicitInstantiation);
   Enum->setAccess(D->getAccess());
+  // Forward the mangling number from the template to the instantiated decl.
+  SemaRef.Context.setManglingNumber(Enum, SemaRef.Context.getManglingNumber(D));
   if (SubstQualifier(D, Enum)) return 0;
   Owner->addDecl(Enum);
 
@@ -1126,6 +1128,10 @@
       SemaRef.CurrentInstantiationScope->InstantiatedLocal(D, Record);
   }
 
+  // Forward the mangling number from the template to the instantiated decl.
+  SemaRef.Context.setManglingNumber(Record,
+                                    SemaRef.Context.getManglingNumber(D));
+
   Owner->addDecl(Record);
   return Record;
 }
@@ -1235,6 +1241,10 @@
   if (D->isLocalExternDecl())
     Function->setLocalExternDecl();
 
+  // Forward the mangling number from the template to the instantiated decl.
+  SemaRef.Context.setManglingNumber(Function,
+                                    SemaRef.Context.getManglingNumber(D));
+
   DeclContext *LexicalDC = Owner;
   if (!isFriend && D->isOutOfLine() && !D->isLocalExternDecl()) {
     assert(D->getDeclContext()->isFileContext());
@@ -1693,6 +1703,10 @@
   if (D->isDeletedAsWritten())
     SemaRef.SetDeclDeleted(Method, Method->getLocation());
 
+  // Forward the mangling number from the template to the instantiated decl.
+  SemaRef.Context.setManglingNumber(Method,
+                                    SemaRef.Context.getManglingNumber(D));
+
   // If there's a function template, let our caller handle it.
   if (FunctionTemplate) {
     // do nothing
@@ -3435,6 +3449,9 @@
     NewVar->setInstantiationOfStaticDataMember(OldVar,
                                                TSK_ImplicitInstantiation);
 
+  // Forward the mangling number from the template to the instantiated decl.
+  Context.setManglingNumber(NewVar, Context.getManglingNumber(OldVar));
+
   // Delay instantiation of the initializer for variable templates until a
   // definition of the variable is needed.
   if (!isa<VarTemplateSpecializationDecl>(NewVar) && !InstantiatingVarTemplate)
Index: test/CodeGenCXX/mangle-template.cpp
===================================================================
--- test/CodeGenCXX/mangle-template.cpp
+++ test/CodeGenCXX/mangle-template.cpp
@@ -182,3 +182,24 @@
   template short returnShort<-32768>();
   // CHECK: @_ZN6test1311returnShortILsn32768EEEsv()
 }
+namespace test14 {
+  template <typename> inline int inl(bool b) {
+    if (b) {
+      static struct {
+        int field;
+      } a;
+      // CHECK: @_ZZN6test143inlIvEEibE1a
+
+      return a.field;
+    } else {
+      static struct {
+        int field;
+      } a;
+      // CHECK: @_ZZN6test143inlIvEEibE1a_0
+
+      return a.field;
+    }
+  }
+
+  int call(bool b) { return inl<void>(b); }
+}
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