From df24e0d185787502a5a38c70b4b94e75d6196332 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Wed, 31 Aug 2011 20:55:20 +0000
Subject: [PATCH] Make sure we aren't deleting the landingpad instruction.

The landingpad instruction is required in the landing pad block. Because we're
not deleting terminating instructions, the invoke may still jump to here (see
Transforms/SCCP/2004-11-16-DeadInvoke.ll). Remove all uses of the landingpad
instruction, but keep it around until code-gen can remove the basic block.

llvm-svn: 138890
---
 lib/Transforms/Scalar/SCCP.cpp | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index cfe750c5fa2..3d52afa2e10 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1681,15 +1681,31 @@ FunctionPass *llvm::createSCCPPass() {
 static void DeleteInstructionInBlock(BasicBlock *BB) {
   DEBUG(dbgs() << "  BasicBlock Dead:" << *BB);
   ++NumDeadBlocks;
-  
+
+  // Check to see if there are non-terminating instructions to delete.
+  if (isa<TerminatorInst>(BB->begin()))
+    return;
+
   // Delete the instructions backwards, as it has a reduced likelihood of
   // having to update as many def-use and use-def chains.
-  while (!isa<TerminatorInst>(BB->begin())) {
-    Instruction *I = --BasicBlock::iterator(BB->getTerminator());
-    
+  std::vector<Instruction*> WorkList;
+  WorkList.reserve(BB->size());
+  BasicBlock::iterator I = --BasicBlock::iterator(BB->getTerminator());
+
+  while (true) {
     if (!I->use_empty())
       I->replaceAllUsesWith(UndefValue::get(I->getType()));
-    BB->getInstList().erase(I);
+    WorkList.push_back(I);
+    if (I == BB->begin())
+      break;
+    --I;
+  }
+
+  for (std::vector<Instruction*>::iterator
+         II = WorkList.begin(), IE = WorkList.end(); II != IE; ++II) {
+    if (isa<LandingPadInst>(*II))
+      continue;
+    BB->getInstList().erase(*II);
     ++NumInstRemoved;
   }
 }