[InstSimplify] Use cast instead of dyn_cast after isa<> check. NFCI

llvm-svn: 299870
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 76ffcf0..807bbd2 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3107,8 +3107,8 @@
   // If both operands have range metadata, use the metadata
   // to simplify the comparison.
   if (isa<Instruction>(RHS) && isa<Instruction>(LHS)) {
-    auto RHS_Instr = dyn_cast<Instruction>(RHS);
-    auto LHS_Instr = dyn_cast<Instruction>(LHS);
+    auto RHS_Instr = cast<Instruction>(RHS);
+    auto LHS_Instr = cast<Instruction>(LHS);
 
     if (RHS_Instr->getMetadata(LLVMContext::MD_range) &&
         LHS_Instr->getMetadata(LLVMContext::MD_range)) {