From 1e6303e60ca5af4fbe7ca728572fd65666a98271 Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Fri, 25 Jun 2021 11:26:15 +0200
Subject: [PATCH] [OpaquePtr] Allow globals with opaque pointer value type

Do this by making opaque pointers a valid pointer element type,
for which we implicitly create an opaque pointer (moving the logic
from getPointerTo into PointerType::get).

We'll never create something like a "pointer to opaque pointer",
but accept it in the API, because a lot of code reasonably assumes
that you can create a pointer to pointer type.

Differential Revision: https://reviews.llvm.org/D104902
---
 llvm/lib/IR/Type.cpp                      | 12 ++++--------
 llvm/test/Assembler/invalid-opaque-ptr.ll |  7 -------
 llvm/test/Assembler/opaque-ptr.ll         |  3 +++
 3 files changed, 7 insertions(+), 15 deletions(-)
 delete mode 100644 llvm/test/Assembler/invalid-opaque-ptr.ll

diff --git a/llvm/lib/IR/Type.cpp b/llvm/lib/IR/Type.cpp
index e7716cd445ea..a7be01415fbf 100644
--- a/llvm/lib/IR/Type.cpp
+++ b/llvm/lib/IR/Type.cpp
@@ -690,7 +690,9 @@ PointerType *PointerType::get(Type *EltTy, unsigned AddressSpace) {
 
   LLVMContextImpl *CImpl = EltTy->getContext().pImpl;
 
-  if (CImpl->ForceOpaquePointers)
+  // Create opaque pointer for pointer to opaque pointer.
+  if (CImpl->ForceOpaquePointers ||
+      (isa<PointerType>(EltTy) && cast<PointerType>(EltTy)->isOpaque()))
     return get(EltTy->getContext(), AddressSpace);
 
   // Since AddressSpace #0 is the common case, we special case it.
@@ -729,19 +731,13 @@ PointerType::PointerType(LLVMContext &C, unsigned AddrSpace)
 }
 
 PointerType *Type::getPointerTo(unsigned AddrSpace) const {
-  // Pointer to opaque pointer is opaque pointer.
-  if (auto *PTy = dyn_cast<PointerType>(this))
-    if (PTy->isOpaque())
-      return PointerType::get(getContext(), AddrSpace);
-
   return PointerType::get(const_cast<Type*>(this), AddrSpace);
 }
 
 bool PointerType::isValidElementType(Type *ElemTy) {
   return !ElemTy->isVoidTy() && !ElemTy->isLabelTy() &&
          !ElemTy->isMetadataTy() && !ElemTy->isTokenTy() &&
-         !ElemTy->isX86_AMXTy() &&
-         !(ElemTy->isPointerTy() && cast<PointerType>(ElemTy)->isOpaque());
+         !ElemTy->isX86_AMXTy();
 }
 
 bool PointerType::isLoadableOrStorableType(Type *ElemTy) {
diff --git a/llvm/test/Assembler/invalid-opaque-ptr.ll b/llvm/test/Assembler/invalid-opaque-ptr.ll
deleted file mode 100644
index 6acb78e9bda7..000000000000
--- a/llvm/test/Assembler/invalid-opaque-ptr.ll
+++ /dev/null
@@ -1,7 +0,0 @@
-; RUN: not llvm-as < %s -disable-output 2>&1 | FileCheck %s
-
-; CHECK: pointer to this type is invalid
-define void @f(ptr %a) {
-    %b = bitcast ptr %a to ptr*
-    ret void
-}
diff --git a/llvm/test/Assembler/opaque-ptr.ll b/llvm/test/Assembler/opaque-ptr.ll
index 62d2d50786db..9167ca9e4586 100644
--- a/llvm/test/Assembler/opaque-ptr.ll
+++ b/llvm/test/Assembler/opaque-ptr.ll
@@ -1,6 +1,9 @@
 ; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
 ; RUN: verify-uselistorder %s
 
+; CHECK: @global = external global ptr
+@global = external global ptr
+
 ; CHECK: define ptr @f(ptr %a) {
 ; CHECK:     %b = bitcast ptr %a to ptr
 ; CHECK:     ret ptr %b