LSR ivchain bug fix: corner case with ConstantExpr.

Fixes PR11950.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153463 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index f2112446ade122563abd26eb28d909aecc73d711..7e71683dc1a4aae77285cd71b749b2479d765558 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -704,8 +704,9 @@ static bool isHighCostExpansion(const SCEV *S,
         Value *UVal = U->getValue();
         for (Value::use_iterator UI = UVal->use_begin(), UE = UVal->use_end();
              UI != UE; ++UI) {
-          Instruction *User = cast<Instruction>(*UI);
-          if (User->getOpcode() == Instruction::Mul
+          // If U is a constant, it may be used by a ConstantExpr.
+          Instruction *User = dyn_cast<Instruction>(*UI);
+          if (User && User->getOpcode() == Instruction::Mul
               && SE.isSCEVable(User->getType())) {
             return SE.getSCEV(User) == Mul;
           }