update the tutorial to use CreateFAdd to create fp operations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112733 91177308-0d34-0410-b5e6-96231b3b80d8

docs/tutorial/LangImpl6.html

@@ -1540,7 +1540,7 @@ Value *ForExprAST::Codegen() {
     StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
   }
   
-  Value *NextVar = Builder.CreateAdd(Variable, StepVal, "nextvar");
+  Value *NextVar = Builder.CreateFAdd(Variable, StepVal, "nextvar");
 
   // Compute the end condition.
   Value *EndCond = End->Codegen();