Fix PR9039, a use-after-free in reassociate. The issue was that the

operand being factorized (and erased) could occur several times in Ops,
resulting in freed memory being used when the next occurrence in Ops was
analyzed.

llvm-svn: 124287

1 files changed, 11 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 46b7f952581..396b3299807 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -811,16 +811,23 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
     // RemoveFactorFromExpression on successive values to behave differently.
     Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
     SmallVector<Value*, 4> NewMulOps;
-    for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+    for (unsigned i = 0; i != Ops.size(); ++i) {
       // Only try to remove factors from expressions we're allowed to.
       BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
       if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
         continue;
       
       if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
-        NewMulOps.push_back(V);
-        Ops.erase(Ops.begin()+i);
-        --i; --e;
+        // The factorized operand may occur several times.  Convert them all in
+        // one fell swoop.
+        for (unsigned j = Ops.size(); j != i;) {
+          --j;
+          if (Ops[j].Op == Ops[i].Op) {
+            NewMulOps.push_back(V);
+            Ops.erase(Ops.begin()+j);
+          }
+        }
+        --i;
       }
     }