Index: lib/IR/Value.cpp
===================================================================
--- lib/IR/Value.cpp
+++ lib/IR/Value.cpp
@@ -773,6 +773,8 @@
 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
   assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
   assert(Old != New && "Changing value into itself!");
+  assert(Old->getType() == New->getType() &&
+         "replaceAllUses of value with new value of different type!");
 
   // Get the linked list base, which is guaranteed to exist since the
   // HasValueHandle flag is set.
Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1286,7 +1286,7 @@
       if (!Caller->use_empty() &&
           // void -> non-void is handled specially
           !NewRetTy->isVoidTy())
-      return false;   // Cannot transform this return value.
+        return false;   // Cannot transform this return value.
     }
 
     if (!CallerPAL.isEmpty() && !Caller->use_empty()) {
@@ -1505,8 +1505,14 @@
 
   if (!Caller->use_empty())
     ReplaceInstUsesWith(*Caller, NV);
-  else if (Caller->hasValueHandle())
-    ValueHandleBase::ValueIsRAUWd(Caller, NV);
+  else if (Caller->hasValueHandle()) {
+    if (OldRetTy == NV->getType())
+      ValueHandleBase::ValueIsRAUWd(Caller, NV);
+    else
+      // We cannot call ValueIsRAUWd with a different type, and the
+      // actual tracked value will disappear.
+      ValueHandleBase::ValueIsDeleted(Caller);
+  }
 
   EraseInstFromFunction(*Caller);
   return true;
Index: test/DebugInfo/voidMDNode.ll
===================================================================
--- /dev/null
+++ test/DebugInfo/voidMDNode.ll
@@ -0,0 +1,63 @@
+; RUN: opt -instcombine < %s | FileCheck %s
+
+; IR generated from (the obvisouly wrong):
+; void foo(void) {}
+; void baz() {
+;       int deadvar = ((int (*)(void))&foo)();
+; }
+; and optimized with just -mem2reg
+
+define void @foo() #0 {
+entry:
+  ret void, !dbg !17
+}
+
+; Function Attrs: nounwind ssp uwtable
+define void @baz() #0 {
+entry:
+  %call = call i32 bitcast (void ()* @foo to i32 ()*)(), !dbg !18
+; Check that when instcombine removes the const bitcast in the call
+; instruction, it doesn't RAUW the %call value with the replacement
+; instruction that is of void type. Metadata referenceing a void operand
+; would be rendered as <badref>.
+; CHECK-NOT: <badref>
+  call void @llvm.dbg.value(metadata !{i32 %call}, i64 0, metadata !19, metadata !20), !dbg !21
+  ret void, !dbg !22
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!14, !15}
+!llvm.ident = !{!16}
+
+!0 = metadata !{metadata !"0x11\0012\00clang version 3.6.0 \000\00\000\00\001", metadata !1, metadata !2, metadata !3, metadata !8, metadata !2, metadata !2} ; [ DW_TAG_compile_unit ] [/tmp/voidmetadata.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"voidmetadata.c", metadata !"/tmp"}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{metadata !"0xf\00\000\0064\0064\000\000", null, null, metadata !5} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from ]
+!5 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !6, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!6 = metadata !{metadata !7}
+!7 = metadata !{metadata !"0x24\00int\000\0032\0032\000\000\005", null, null} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!8 = metadata !{metadata !9, metadata !13}
+!9 = metadata !{metadata !"0x2e\00foo\00foo\00\002\000\001\000\000\00256\000\002", metadata !1, metadata !10, metadata !11, null, void ()* @foo, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 2] [def] [foo]
+!10 = metadata !{metadata !"0x29", metadata !1}   ; [ DW_TAG_file_type ] [/tmp/voidmetadata.c]
+!11 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null, null, null, metadata !12, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!12 = metadata !{null}
+!13 = metadata !{metadata !"0x2e\00baz\00baz\00\004\000\001\000\000\000\000\004", metadata !1, metadata !10, metadata !11, null, void ()* @baz, null, null, metadata !2} ; [ DW_TAG_subprogram ] [line 4] [def] [baz]
+!14 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!15 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
+!16 = metadata !{metadata !"clang version 3.6.0 "}
+!17 = metadata !{i32 2, i32 17, metadata !9, null}
+!18 = metadata !{i32 5, i32 16, metadata !13, null}
+!19 = metadata !{metadata !"0x100\00deadvar\005\000", metadata !13, metadata !10, metadata !7} ; [ DW_TAG_auto_variable ] [deadvar] [line 5]
+!20 = metadata !{metadata !"0x102"}               ; [ DW_TAG_expression ]
+!21 = metadata !{i32 5, i32 6, metadata !13, null}
+!22 = metadata !{i32 6, i32 1, metadata !13, null}