r337540 - Sema: Fix explicit address space cast in C++

[Richard Smith via cfe-commits]

On Fri, 20 Jul 2018 at 04:38, Yaxun Liu via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: yaxunl
> Date: Fri Jul 20 04:32:51 2018
> New Revision: 337540
>
> URL: http://llvm.org/viewvc/llvm-project?rev=337540&view=rev
> Log:
> 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
>
> Added:
>     cfe/trunk/test/CodeGenCXX/address-space-cast.cpp
> Modified:
>     cfe/trunk/lib/Sema/SemaCast.cpp
>     cfe/trunk/lib/Sema/SemaOverload.cpp
>
> Modified: cfe/trunk/lib/Sema/SemaCast.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCast.cpp?rev=337540&r1=337539&r2=337540&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaCast.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaCast.cpp Fri Jul 20 04:32:51 2018
> @@ -1955,6 +1955,12 @@ static bool fixOverloadedReinterpretCast
>    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(
>      } else {
>        Kind = CK_BitCast;
>      }
> +  } else if (IsAddressSpaceConversion(SrcType, DestType)) {
> +    Kind = CK_AddressSpaceConversion;
>

This seems wrong to me. A reinterpret_cast from a pointer to one address
space into a pointer to a different address space should be a bit cast, not
an address space conversion.


>    } else {
>      Kind = CK_BitCast;
>    }
>
> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=337540&r1=337539&r2=337540&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Fri Jul 20 04:32:51 2018
> @@ -3150,6 +3150,15 @@ Sema::IsQualificationConversion(QualType
>        = 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
>
> Added: cfe/trunk/test/CodeGenCXX/address-space-cast.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/address-space-cast.cpp?rev=337540&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/address-space-cast.cpp (added)
> +++ cfe/trunk/test/CodeGenCXX/address-space-cast.cpp Fri Jul 20 04:32:51
> 2018
> @@ -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);
> +}
>
>
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