IR: Don't allow non-default visibility on local linkage

Visibilities of `hidden` and `protected` are meaningless for symbols
with local linkage.

  - Change the assembler to reject non-default visibility on symbols
    with local linkage.

  - Change the bitcode reader to auto-upgrade `hidden` and `protected`
    to `default` when the linkage is local.

  - Update LangRef.

<rdar://problem/16141113>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208263 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 56422393e4..32037df958 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -622,6 +622,11 @@ bool LLParser::ParseStandaloneMetadata() {
   return false;
 }
 
+static bool isValidVisibilityForLinkage(unsigned V, unsigned L) {
+  return !GlobalValue::isLocalLinkage((GlobalValue::LinkageTypes)L) ||
+         (GlobalValue::VisibilityTypes)V == GlobalValue::DefaultVisibility;
+}
+
 /// ParseAlias:
 ///   ::= GlobalVar '=' OptionalVisibility OptionalDLLStorageClass 'alias'
 ///                     OptionalLinkage Aliasee
@@ -646,6 +651,10 @@ bool LLParser::ParseAlias(const std::string &Name, LocTy NameLoc,
   if(!GlobalAlias::isValidLinkage(Linkage))
     return Error(LinkageLoc, "invalid linkage type for alias");
 
+  if (!isValidVisibilityForLinkage(Visibility, L))
+    return Error(LinkageLoc,
+                 "symbol with local linkage must have default visibility");
+
   Constant *Aliasee;
   LocTy AliaseeLoc = Lex.getLoc();
   if (Lex.getKind() != lltok::kw_bitcast &&
@@ -714,6 +723,10 @@ bool LLParser::ParseAlias(const std::string &Name, LocTy NameLoc,
 bool LLParser::ParseGlobal(const std::string &Name, LocTy NameLoc,
                            unsigned Linkage, bool HasLinkage,
                            unsigned Visibility, unsigned DLLStorageClass) {
+  if (!isValidVisibilityForLinkage(Visibility, Linkage))
+    return Error(NameLoc,
+                 "symbol with local linkage must have default visibility");
+
   unsigned AddrSpace;
   bool IsConstant, UnnamedAddr, IsExternallyInitialized;
   GlobalVariable::ThreadLocalMode TLM;
@@ -3014,6 +3027,10 @@ bool LLParser::ParseFunctionHeader(Function *&Fn, bool isDefine) {
     return Error(LinkageLoc, "invalid function linkage type");
   }
 
+  if (!isValidVisibilityForLinkage(Visibility, Linkage))
+    return Error(LinkageLoc,
+                 "symbol with local linkage must have default visibility");
+
   if (!FunctionType::isValidReturnType(RetType))
     return Error(RetTypeLoc, "invalid function return type");