Change CallLoweringInfo::CS to be an ImmutableCallSite instead of a pointer. NFCI.

This was a use-after-free waiting to happen.

llvm-svn: 309159
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 21df22c..7724a75 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -314,7 +314,7 @@
   // required, fail. Otherwise, just disable them.
   if ((CallConv == CallingConv::Fast && CLI.IsTailCall &&
        MF.getTarget().Options.GuaranteedTailCallOpt) ||
-      (CLI.CS && CLI.CS->isMustTailCall()))
+      (CLI.CS && CLI.CS.isMustTailCall()))
     fail(DL, DAG, "WebAssembly doesn't support tail call yet");
   CLI.IsTailCall = false;