From 99a9f75948598a41afaf2ca1b3277593f4fd54b2 Mon Sep 17 00:00:00 2001
From: Yaxun Liu <Yaxun.Liu@amd.com>
Date: Fri, 20 Jul 2018 11:32:51 +0000
Subject: [PATCH] Sema: Fix explicit address space cast in C++

Currently clang does not allow implicit cast of a pointer to a pointer type
in different address space but allows C-style cast of a pointer to a pointer
type in different address space. However, there is a bug in Sema causing
incorrect Cast Expr in AST for the latter case, which in turn results in
invalid LLVM IR in codegen.

This is because Sema::IsQualificationConversion returns true for a cast of
pointer to a pointer type in different address space, which in turn allows
a standard conversion and results in a cast expression with no op in AST.

This patch fixes that by let Sema::IsQualificationConversion returns false
for a cast of pointer to a pointer type in different address space, which
in turn disallows standard conversion, implicit cast, and static cast.
Finally it results in an reinterpret cast and correct conversion kind is set.

Differential Revision: https://reviews.llvm.org/D49294

llvm-svn: 337540
---
 clang/lib/Sema/SemaCast.cpp                  |  8 ++++++++
 clang/lib/Sema/SemaOverload.cpp              |  9 +++++++++
 clang/test/CodeGenCXX/address-space-cast.cpp | 15 +++++++++++++++
 3 files changed, 32 insertions(+)
 create mode 100644 clang/test/CodeGenCXX/address-space-cast.cpp

diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index 86633d6..b3f6be4 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -1955,6 +1955,12 @@ static bool fixOverloadedReinterpretCastExpr(Sema &Self, QualType DestType,
   return Result.isUsable();
 }
 
+static bool IsAddressSpaceConversion(QualType SrcType, QualType DestType) {
+  return SrcType->isPointerType() && DestType->isPointerType() &&
+         SrcType->getAs<PointerType>()->getPointeeType().getAddressSpace() !=
+             DestType->getAs<PointerType>()->getPointeeType().getAddressSpace();
+}
+
 static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
                                         QualType DestType, bool CStyle,
                                         SourceRange OpRange,
@@ -2198,6 +2204,8 @@ static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
     } else {
       Kind = CK_BitCast;
     }
+  } else if (IsAddressSpaceConversion(SrcType, DestType)) {
+    Kind = CK_AddressSpaceConversion;
   } else {
     Kind = CK_BitCast;
   }
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 822c3c0..390782b 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -3150,6 +3150,15 @@ Sema::IsQualificationConversion(QualType FromType, QualType ToType,
       = PreviousToQualsIncludeConst && ToQuals.hasConst();
   }
 
+  // Allows address space promotion by language rules implemented in
+  // Type::Qualifiers::isAddressSpaceSupersetOf.
+  Qualifiers FromQuals = FromType.getQualifiers();
+  Qualifiers ToQuals = ToType.getQualifiers();
+  if (!ToQuals.isAddressSpaceSupersetOf(FromQuals) &&
+      !FromQuals.isAddressSpaceSupersetOf(ToQuals)) {
+    return false;
+  }
+
   // We are left with FromType and ToType being the pointee types
   // after unwrapping the original FromType and ToType the same number
   // of types. If we unwrapped any pointers, and if FromType and
diff --git a/clang/test/CodeGenCXX/address-space-cast.cpp b/clang/test/CodeGenCXX/address-space-cast.cpp
new file mode 100644
index 0000000..334a1a6
--- /dev/null
+++ b/clang/test/CodeGenCXX/address-space-cast.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 %s -triple=amdgcn-amd-amdhsa -emit-llvm -o - | FileCheck %s
+
+#define __private__ __attribute__((address_space(5)))
+
+void func_pchar(__private__ char *x);
+
+void test_cast(char *gen_ptr) {
+  // CHECK: %[[cast:.*]] = addrspacecast i8* %{{.*}} to i8 addrspace(5)*
+  // CHECK-NEXT: store i8 addrspace(5)* %[[cast]]
+  __private__ char *priv_ptr = (__private__ char *)gen_ptr;
+
+  // CHECK: %[[cast:.*]] = addrspacecast i8* %{{.*}} to i8 addrspace(5)*
+  // CHECK-NEXT: call void @_Z10func_pcharPU3AS5c(i8 addrspace(5)* %[[cast]])
+  func_pchar((__private__ char *)gen_ptr);
+}
-- 
2.7.4