[opaque pointer type] Avoid using PointerType::getElementType when parsing IR

A few calls are left in for error checking - but I'm commenting those
out & trying to build some IR tests (aiming for Argument Promotion to
start with). When I get any of these tests passing I may add flag to
disable the checking so I can add tests that pass with the assertion in
place.

llvm-svn: 234206
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index f1dfea9..8e3ddaa 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -943,12 +943,10 @@
     : LoadInst(Ptr, Name, isVolatile, Align, NotAtomic, CrossThread, InsertAE) {
 }
 
-LoadInst::LoadInst(Value *Ptr, const Twine &Name, bool isVolatile, 
+LoadInst::LoadInst(Type *Ty, Value *Ptr, const Twine &Name, bool isVolatile,
                    unsigned Align, AtomicOrdering Order,
-                   SynchronizationScope SynchScope,
-                   Instruction *InsertBef)
-  : UnaryInstruction(cast<PointerType>(Ptr->getType())->getElementType(),
-                     Load, Ptr, InsertBef) {
+                   SynchronizationScope SynchScope, Instruction *InsertBef)
+    : UnaryInstruction(Ty, Load, Ptr, InsertBef) {
   setVolatile(isVolatile);
   setAlignment(Align);
   setAtomic(Order, SynchScope);