[IR] Deprecate Type::getPointerTo() (NFC)

[JOE1994]

Summary

According to discussion from D152173, the current plan is to eventually
get rid of Type::getPointerTo.

Deprecate Type::getPointerTo to discourage use of the API.

[nikic]

Deprecation requires removing all in-tree users first.

[JOE1994]

Deprecation requires removing all in-tree users first.

Thanks for your feedback. I'll close this revision, and come back later with commits replacing current uses of getPointerTo.

llvm/include/llvm/IR/Type.h

 //===- llvm/Type.h - Classes for handling data types ------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
public:
   static PointerType *getInt32PtrTy(LLVMContext &C, unsigned AS = 0);
   static PointerType *getInt64PtrTy(LLVMContext &C, unsigned AS = 0);
   static Type *getWasm_ExternrefTy(LLVMContext &C);
   static Type *getWasm_FuncrefTy(LLVMContext &C);
 
   /// Return a pointer to the current type. This is equivalent to
   /// PointerType::get(Foo, AddrSpace).
   /// TODO: Remove this after opaque pointer transition is complete.
+  [[deprecated("Use 'PointerType::get(Ty, AddrSpace)' instead")]]
   PointerType *getPointerTo(unsigned AddrSpace = 0) const;
 
 private:
   /// Derived types like structures and arrays are sized iff all of the members
   /// of the type are sized as well. Since asking for their size is relatively
   /// uncommon, move this operation out-of-line.
   bool isSizedDerivedType(SmallPtrSetImpl<Type*> *Visited = nullptr) const;
 };