only factor from expressions whose uses are empty and whose
base is the right expression type.  This fixes PR5981.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93045 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index 3cc380a..4a99f4a 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -792,6 +792,11 @@
     Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
     SmallVector<Value*, 4> NewMulOps;
     for (unsigned i = 0, e = Ops.size(); i != e; ++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);