From 82258b45e4f6974d5442b0b48ff3ed6f61b14a05 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 9 Dec 2014 05:43:56 +0000
Subject: [PATCH] AsmParser: Reject invalid mismatch between forward ref and
 def

Don't assume that the forward referenced entity was of the same
global-kind as the new entity.

This fixes PR21779.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223754 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AsmParser/LLParser.cpp        | 13 ++++++++-----
 test/Assembler/invalid-fwdref2.ll |  4 ++++
 2 files changed, 12 insertions(+), 5 deletions(-)
 create mode 100644 test/Assembler/invalid-fwdref2.ll

diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index e1c00cc4af0..df4a16abe1c 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -787,33 +787,36 @@ bool LLParser::ParseGlobal(const std::string &Name, LocTy NameLoc,
   if (Ty->isFunctionTy() || Ty->isLabelTy())
     return Error(TyLoc, "invalid type for global variable");
 
-  GlobalVariable *GV = nullptr;
+  GlobalValue *GVal = nullptr;
 
   // See if the global was forward referenced, if so, use the global.
   if (!Name.empty()) {
-    if (GlobalValue *GVal = M->getNamedValue(Name)) {
+    GVal = M->getNamedValue(Name);
+    if (GVal) {
       if (!ForwardRefVals.erase(Name) || !isa<GlobalValue>(GVal))
         return Error(NameLoc, "redefinition of global '@" + Name + "'");
-      GV = cast<GlobalVariable>(GVal);
     }
   } else {
     std::map<unsigned, std::pair<GlobalValue*, LocTy> >::iterator
       I = ForwardRefValIDs.find(NumberedVals.size());
     if (I != ForwardRefValIDs.end()) {
-      GV = cast<GlobalVariable>(I->second.first);
+      GVal = I->second.first;
       ForwardRefValIDs.erase(I);
     }
   }
 
+  GlobalVariable *GV;
   if (!GV) {
     GV = new GlobalVariable(*M, Ty, false, GlobalValue::ExternalLinkage, nullptr,
                             Name, nullptr, GlobalVariable::NotThreadLocal,
                             AddrSpace);
   } else {
-    if (GV->getType()->getElementType() != Ty)
+    if (GVal->getType()->getElementType() != Ty)
       return Error(TyLoc,
             "forward reference and definition of global have different types");
 
+    GV = cast<GlobalVariable>(GVal);
+
     // Move the forward-reference to the correct spot in the module.
     M->getGlobalList().splice(M->global_end(), M->getGlobalList(), GV);
   }
diff --git a/test/Assembler/invalid-fwdref2.ll b/test/Assembler/invalid-fwdref2.ll
new file mode 100644
index 00000000000..d823481f8e1
--- /dev/null
+++ b/test/Assembler/invalid-fwdref2.ll
@@ -0,0 +1,4 @@
+; RUN: not llvm-as %s -disable-output 2>&1 | grep "forward reference and definition of global have different types"
+
+@a2 = alias void ()* @g2
+@g2 = internal global i8 42