From 465c3bed165dc76452606ea10a34ae2ef6033e8a Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Fri, 6 Nov 2009 01:30:04 +0000
Subject: [PATCH] Do not try to emit debug info entry for dead global variable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86212 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/AsmPrinter/DwarfDebug.cpp           |  7 ++++++-
 test/DebugInfo/2009-11-05-DeadGlobalVariable.ll | 17 +++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/DebugInfo/2009-11-05-DeadGlobalVariable.ll

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1372fc21685..6b54e618c3d 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1097,6 +1097,10 @@ DIE *DwarfDebug::ConstructEnumTypeDIE(CompileUnit *DW_Unit, DIEnumerator *ETy) {
 /// CreateGlobalVariableDIE - Create new DIE using GV.
 DIE *DwarfDebug::CreateGlobalVariableDIE(CompileUnit *DW_Unit,
                                          const DIGlobalVariable &GV) {
+  // If the global variable was optmized out then no need to create debug info entry.
+  if (!GV.getGlobal())
+    return NULL;
+
   DIE *GVDie = new DIE(dwarf::DW_TAG_variable);
   AddString(GVDie, dwarf::DW_AT_name, dwarf::DW_FORM_string, 
             GV.getDisplayName());
@@ -1518,7 +1522,8 @@ void DwarfDebug::ConstructFunctionDbgScope(DbgScope *RootScope,
     DIGlobalVariable GV(N);
     if (GV.getContext().getNode() == RootScope->getDesc().getNode()) {
       DIE *ScopedGVDie = CreateGlobalVariableDIE(ModuleCU, GV);
-      SPDie->AddChild(ScopedGVDie);
+      if (ScopedGVDie)
+        SPDie->AddChild(ScopedGVDie);
     }
   }
 }
diff --git a/test/DebugInfo/2009-11-05-DeadGlobalVariable.ll b/test/DebugInfo/2009-11-05-DeadGlobalVariable.ll
new file mode 100644
index 00000000000..c7838c54884
--- /dev/null
+++ b/test/DebugInfo/2009-11-05-DeadGlobalVariable.ll
@@ -0,0 +1,17 @@
+; RUN: llc %s -o /dev/null
+; Here variable bar is optimzied away. Do not trip over while trying to generate debug info.
+
+define i32 @foo() nounwind readnone optsize ssp {
+entry:
+  ret i32 42, !dbg !6
+}
+
+!llvm.dbg.gv = !{!0}
+
+!0 = metadata !{i32 458804, i32 0, metadata !1, metadata !"foo.bar", metadata !"foo.bar", metadata !"foo.bar", metadata !2, i32 3, metadata !5, i1 true, i1 true, null}; [DW_TAG_variable ]
+!1 = metadata !{i32 458798, i32 0, metadata !2, metadata !"foo", metadata !"foo", metadata !"foo", metadata !2, i32 2, metadata !3, i1 false, i1 true}; [DW_TAG_subprogram ]
+!2 = metadata !{i32 458769, i32 0, i32 12, metadata !"st.c", metadata !"/private/tmp", metadata !"clang 1.1", i1 true, i1 true, metadata !"", i32 0}; [DW_TAG_compile_unit ]
+!3 = metadata !{i32 458773, metadata !2, metadata !"", null, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !4, i32 0}; [DW_TAG_subroutine_type ]
+!4 = metadata !{metadata !5}
+!5 = metadata !{i32 458788, metadata !2, metadata !"int", metadata !2, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5}; [DW_TAG_base_type ]
+!6 = metadata !{i32 5, i32 1, metadata !1, null}