[PATCH] Use dereferencable attribute in Clang for C++ references

[Aaron Ballman]

On Fri, Jul 11, 2014 at 1:50 AM, hfinkel at anl.gov <hfinkel at anl.gov> wrote:
> Fixed up the remaining regression tests (now all pass), and added a new test for dereferenceable/nonnull on non-addrspace(0) references.
>
> http://reviews.llvm.org/D4450
>
> Files:
>   lib/CodeGen/CGCall.cpp
>   test/CXX/except/except.spec/p14-ir.cpp
>   test/CodeGenCXX/address-space-ref.cpp
>   test/CodeGenCXX/blocks-cxx11.cpp
>   test/CodeGenCXX/blocks.cpp
>   test/CodeGenCXX/catch-undef-behavior.cpp
>   test/CodeGenCXX/conditional-gnu-ext.cpp
>   test/CodeGenCXX/const-init-cxx11.cpp
>   test/CodeGenCXX/constructor-direct-call.cpp
>   test/CodeGenCXX/constructor-init.cpp
>   test/CodeGenCXX/convert-to-fptr.cpp
>   test/CodeGenCXX/copy-assign-synthesis-1.cpp
>   test/CodeGenCXX/copy-constructor-elim-2.cpp
>   test/CodeGenCXX/copy-constructor-synthesis-2.cpp
>   test/CodeGenCXX/copy-constructor-synthesis.cpp
>   test/CodeGenCXX/cxx11-initializer-aggregate.cpp
>   test/CodeGenCXX/cxx11-thread-local-reference.cpp
>   test/CodeGenCXX/decl-ref-init.cpp
>   test/CodeGenCXX/default-arg-temps.cpp
>   test/CodeGenCXX/derived-to-base-conv.cpp
>   test/CodeGenCXX/derived-to-virtual-base-class-calls-final.cpp
>   test/CodeGenCXX/dllexport-members.cpp
>   test/CodeGenCXX/dllexport.cpp
>   test/CodeGenCXX/dllimport-members.cpp
>   test/CodeGenCXX/dllimport.cpp
>   test/CodeGenCXX/eh.cpp
>   test/CodeGenCXX/empty-nontrivially-copyable.cpp
>   test/CodeGenCXX/exceptions.cpp
>   test/CodeGenCXX/fastcall.cpp
>   test/CodeGenCXX/goto.cpp
>   test/CodeGenCXX/implicit-copy-assign-operator.cpp
>   test/CodeGenCXX/implicit-copy-constructor.cpp
>   test/CodeGenCXX/mangle-lambdas.cpp
>   test/CodeGenCXX/mangle.cpp
>   test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
>   test/CodeGenCXX/microsoft-abi-static-initializers.cpp
>   test/CodeGenCXX/nrvo.cpp
>   test/CodeGenCXX/pod-member-memcpys.cpp
>   test/CodeGenCXX/pointers-to-data-members.cpp
>   test/CodeGenCXX/reference-cast.cpp
>   test/CodeGenCXX/rvalue-references.cpp
>   test/CodeGenCXX/temporaries.cpp
>   test/CodeGenCXX/throw-expressions.cpp
>   test/CodeGenCXX/volatile.cpp
>   test/CodeGenObjC/return-objc-object.mm
>   test/CodeGenObjCXX/arc-blocks.mm
>   test/CodeGenObjCXX/arc-move.mm
>   test/CodeGenObjCXX/arc-special-member-functions.mm
>   test/CodeGenObjCXX/implicit-copy-assign-operator.mm
>   test/CodeGenObjCXX/implicit-copy-constructor.mm
>   test/CodeGenObjCXX/lvalue-reference-getter.mm
>   test/CodeGenObjCXX/message-reference.mm
>   test/CodeGenObjCXX/property-dot-reference.mm
>   test/CodeGenObjCXX/property-lvalue-capture.mm
>   test/CodeGenObjCXX/property-object-reference-2.mm
>   test/CodeGenObjCXX/property-objects.mm
>   test/CodeGenObjCXX/property-reference.mm
>   test/Modules/templates.mm

I have no real comments on whether this is the correct approach or
not, but I do have a small style nit:

> Index: lib/CodeGen/CGCall.cpp
> ===================================================================
> --- lib/CodeGen/CGCall.cpp
> +++ lib/CodeGen/CGCall.cpp
> @@ -1200,8 +1200,14 @@
>      llvm_unreachable("Invalid ABI kind for return argument");
>    }
>
> -  if (RetTy->isReferenceType())
> -    RetAttrs.addAttribute(llvm::Attribute::NonNull);
> +  if (RetTy->isReferenceType()) {
> +    QualType PTy = RetTy->getAs<ReferenceType>()->getPointeeType();

if (const auto *RefTy = RetTy->getAs<ReferenceType>()) {
  QualType Pty = RefTy->getPointeeType();
  ...

> +    if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
> +      RetAttrs.addDereferenceableAttr(getContext().getTypeSizeInChars(PTy)
> +                                        .getQuantity());
> +    else if (getContext().getTargetAddressSpace(PTy) == 0)
> +      RetAttrs.addAttribute(llvm::Attribute::NonNull);
> +  }
>
>    if (RetAttrs.hasAttributes())
>      PAL.push_back(llvm::
> @@ -1291,8 +1297,14 @@
>      }
>      }
>
> -    if (ParamType->isReferenceType())
> -      Attrs.addAttribute(llvm::Attribute::NonNull);
> +    if (ParamType->isReferenceType()) {
> +      QualType PTy = ParamType->getAs<ReferenceType>()->getPointeeType();

Same here as above.

> +      if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
> +        Attrs.addDereferenceableAttr(getContext().getTypeSizeInChars(PTy)
> +                                       .getQuantity());
> +      else if (getContext().getTargetAddressSpace(PTy) == 0)
> +        Attrs.addAttribute(llvm::Attribute::NonNull);
> +    }

~Aaron