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

2 files changed, 8 insertions, 7 deletions

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index ad7d5fcc33..d0dcc708d0 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -978,17 +978,18 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
           }
 
           // Iterate through all the predecessors, revectoring each in-turn.
-          MachineBasicBlock::pred_iterator PI = MBB->pred_begin();
+          size_t PI = 0;
           bool DidChange = false;
           bool HasBranchToSelf = false;
-          while (PI != MBB->pred_end()) {
-            if (*PI == MBB) {
+          while(PI != MBB->pred_size()) {
+            MachineBasicBlock *PMBB = *(MBB->pred_begin() + PI);
+            if (PMBB == MBB) {
               // If this block has an uncond branch to itself, leave it.
               ++PI;
               HasBranchToSelf = true;
             } else {
               DidChange = true;
-              (*PI)->ReplaceUsesOfBlockWith(MBB, CurTBB);
+              PMBB->ReplaceUsesOfBlockWith(MBB, CurTBB);
             }
           }
 
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index da062b1559..ba428c5bdb 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -176,10 +176,10 @@ void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
   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 @@ bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
       ++SI;
     } else {
       // Otherwise, this is a superfluous edge, remove it.
-      removeSuccessor(SI);
+      SI = removeSuccessor(SI);
       MadeChange = true;
     }
   }