Fix misue of iterator pointing to erased object.  Uncovered by
_GLIBCXX_DEBUG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37793 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index da062b1..ba428c5 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -176,10 +176,10 @@
   Successors.erase(I);
 }
 
-void MachineBasicBlock::removeSuccessor(succ_iterator I) {
+MachineBasicBlock::succ_iterator MachineBasicBlock::removeSuccessor(succ_iterator I) {
   assert(I != Successors.end() && "Not a current successor!");
   (*I)->removePredecessor(this);
-  Successors.erase(I);
+  return(Successors.erase(I));
 }
 
 void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
@@ -273,7 +273,7 @@
       ++SI;
     } else {
       // Otherwise, this is a superfluous edge, remove it.
-      removeSuccessor(SI);
+      SI = removeSuccessor(SI);
       MadeChange = true;
     }
   }