From 9c5822a966572ea78f4e818870d4229c7a855749 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Fri, 18 Mar 2011 23:28:02 +0000
Subject: [PATCH] Consider debug info intrinsics pointing to null value as dead
 instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127922 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/Local.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index e54dfb3dc73..19b999722db 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -211,7 +211,20 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
 bool llvm::isInstructionTriviallyDead(Instruction *I) {
   if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
 
-  // We don't want debug info removed by anything this general.
+  // We don't want debug info removed by anything this general, unless
+  // debug info is empty.
+  if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
+    if (DDI->getAddress()) 
+      return false;
+    else
+      return true;
+  } else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
+    if (DVI->getValue())
+      return false;
+    else
+      return true;
+  }
+
   if (isa<DbgInfoIntrinsic>(I)) return false;
 
   if (!I->mayHaveSideEffects()) return true;