8 files changed, 64 insertions, 5 deletions
diff --git a/include/llvm/AutoUpgrade.h b/include/llvm/AutoUpgrade.h
index b638d4f590..c774782f19 100644
--- a/include/llvm/AutoUpgrade.h
+++ b/include/llvm/AutoUpgrade.h
@@ -57,6 +57,10 @@ namespace llvm {
   /// with different address spaces: the instruction is replaced by a pair
   /// ptrtoint+inttoptr.
   Value *UpgradeBitCastExpr(unsigned Opc, Constant *C, Type *DestTy);
+
+  /// Check the debug info version number, if it is out-dated, drop the debug
+  /// info. Return true if module is modified.
+  bool UpgradeDebugInfo(Module &M);
 } // End llvm namespace
 
 #endif
diff --git a/include/llvm/DebugInfo.h b/include/llvm/DebugInfo.h
index 0ff7d85682..7c4c1123b5 100644
--- a/include/llvm/DebugInfo.h
+++ b/include/llvm/DebugInfo.h
@@ -759,6 +759,9 @@ DITypeIdentifierMap generateDITypeIdentifierMap(const NamedMDNode *CU_Nodes);
 /// Return true if module is modified.
 bool StripDebugInfo(Module &M);
 
+/// Return Debug Info Version by checking module flags.
+unsigned getDebugInfoVersionFromModule(const Module &M);
+
 /// DebugInfoFinder tries to list all debug info MDNodes used in a module. To
 /// list debug info MDNodes used by an instruction, DebugInfoFinder uses
 /// processDeclare, processValue and processLocation to handle DbgDeclareInst,
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 20fa0f4eab..3b903cdb09 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -182,6 +182,8 @@ bool LLParser::ValidateEndOfModule() {
   for (Module::iterator FI = M->begin(), FE = M->end(); FI != FE; )
     UpgradeCallsToIntrinsic(FI++); // must be post-increment, as we remove
 
+  UpgradeDebugInfo(*M);
+
   return false;
 }
 
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 2c95c920f8..ce3b7d163e 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3152,6 +3152,7 @@ error_code BitcodeReader::MaterializeModule(Module *M) {
   for (unsigned I = 0, E = InstsWithTBAATag.size(); I < E; I++)
     UpgradeInstWithTBAATag(InstsWithTBAATag[I]);
 
+  UpgradeDebugInfo(*M);
   return error_code::success();
 }
 
diff --git a/lib/IR/AutoUpgrade.cpp b/lib/IR/AutoUpgrade.cpp
index 6f79919f24..32cfe278c7 100644
--- a/lib/IR/AutoUpgrade.cpp
+++ b/lib/IR/AutoUpgrade.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/AutoUpgrade.h"
+#include "llvm/DebugInfo.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
@@ -489,3 +490,12 @@ Value *llvm::UpgradeBitCastExpr(unsigned Opc, Constant *C, Type *DestTy) {
 
   return 0;
 }
+
+/// Check the debug info version number, if it is out-dated, drop the debug
+/// info. Return true if module is modified.
+bool llvm::UpgradeDebugInfo(Module &M) {
+  if (getDebugInfoVersionFromModule(M) == DEBUG_METADATA_VERSION)
+    return false;
+
+  return StripDebugInfo(M);
+}
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index 0c262024ff..68015b759a 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -1477,3 +1477,11 @@ bool llvm::StripDebugInfo(Module &M) {
 
   return Changed;
 }
+
+/// Return Debug Info Version by checking module flags.
+unsigned llvm::getDebugInfoVersionFromModule(const Module &M) {
+  Value *Val = M.getModuleFlag("Debug Info Version");
+  if (!Val)
+    return 0;
+  return cast<ConstantInt>(Val)->getZExtValue();
+}
diff --git a/lib/IR/Module.cpp b/lib/IR/Module.cpp
index 3dd1f7e810..4f240c783e 100644
--- a/lib/IR/Module.cpp
+++ b/lib/IR/Module.cpp
@@ -318,11 +318,16 @@ getModuleFlagsMetadata(SmallVectorImpl<ModuleFlagEntry> &Flags) const {
 
   for (unsigned i = 0, e = ModFlags->getNumOperands(); i != e; ++i) {
     MDNode *Flag = ModFlags->getOperand(i);
-    ConstantInt *Behavior = cast<ConstantInt>(Flag->getOperand(0));
-    MDString *Key = cast<MDString>(Flag->getOperand(1));
-    Value *Val = Flag->getOperand(2);
-    Flags.push_back(ModuleFlagEntry(ModFlagBehavior(Behavior->getZExtValue()),
-                                    Key, Val));
+    if (Flag->getNumOperands() >= 3 && isa<ConstantInt>(Flag->getOperand(0)) &&
+        isa<MDString>(Flag->getOperand(1))) {
+      // Check the operands of the MDNode before accessing the operands.
+      // The verifier will actually catch these failures.
+      ConstantInt *Behavior = cast<ConstantInt>(Flag->getOperand(0));
+      MDString *Key = cast<MDString>(Flag->getOperand(1));
+      Value *Val = Flag->getOperand(2);
+      Flags.push_back(ModuleFlagEntry(ModFlagBehavior(Behavior->getZExtValue()),
+                                      Key, Val));
+    }
   }
 }
 
diff --git a/test/Bitcode/drop-debug-info.ll b/test/Bitcode/drop-debug-info.ll
new file mode 100644
index 0000000000..da4ae0c541
--- /dev/null
+++ b/test/Bitcode/drop-debug-info.ll
@@ -0,0 +1,26 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+define i32 @main() {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval
+  ret i32 0, !dbg !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 (trunk 195495) (llvm/trunk 195495:195504M)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [/Users/manmanren/llvm_gmail/release/../llvm/tools/clang/test/CodeGen/debug-info-version.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"../llvm/tools/clang/test/CodeGen/debug-info-version.c", metadata !"/Users/manmanren/llvm_gmail/release"}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"main", metadata !"main", metadata !"", i32 3, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 ()* @main, null, null, metadata !2, i32 3} ; [ DW_TAG_subprogram ] [line 3] [def] [main]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/Users/manmanren/llvm_gmail/release/../llvm/tools/clang/test/CodeGen/debug-info-version.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{metadata !8}
+!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!12 = metadata !{i32 4, i32 0, metadata !4, null}
+
+; CHECK-NOT: !dbg
+; CHECK-NOT: !llvm.dbg.cu