[NewGVN] Use a cast instead of a dyn_cast.

[• dberlin]

thank you!

[davide]

LGTM

llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp

if (II && EI->getNumIndices() == 1 && *EI->idx_begin() == 0) {
             Opcode, EI->getType(), II->getArgOperand(0), II->getArgOperand(1));
       }
     }
   }
 
   return createAggregateValueExpression(I);
 }
 const Expression *NewGVN::performSymbolicCmpEvaluation(Instruction *I) const {
-  auto *CI = dyn_cast<CmpInst>(I);
+  assert(isa<CmpInst>(I) && "Expected a cmp instruction.");
+
+  auto *CI = cast<CmpInst>(I);
   // See if our operands are equal to those of a previous predicate, and if so,
   // if it implies true or false.
   auto Op0 = lookupOperandLeader(CI->getOperand(0));
   auto Op1 = lookupOperandLeader(CI->getOperand(1));
   auto OurPredicate = CI->getPredicate();
   if (shouldSwapOperands(Op0, Op1)) {
     std::swap(Op0, Op1);
     OurPredicate = CI->getSwappedPredicate();