Author: Fangrui Song Date: 2020-11-30T12:44:35-08:00 New Revision: 164410324d8bf3b5a99e39f7dfe3c6d6972dab30
URL: https://github.com/llvm/llvm-project/commit/164410324d8bf3b5a99e39f7dfe3c6d6972dab30 DIFF: https://github.com/llvm/llvm-project/commit/164410324d8bf3b5a99e39f7dfe3c6d6972dab30.diff LOG: [CodeGen] -fno-delete-null-pointer-checks: change dereferenceable to dereferenceable_or_null After D17993, with -fno-delete-null-pointer-checks we add the dereferenceable attribute to the `this` pointer. We have observed that one internal target which worked before fails even with -fno-delete-null-pointer-checks. Switching to dereferenceable_or_null fixes the problem. dereferenceable currently does not always respect NullPointerIsValid and may imply nonnull and lead to aggressive optimization. The optimization may be related to `CallBase::isReturnNonNull`, `Argument::hasNonNullAttr`, or `Value::getPointerDereferenceableBytes`. See D66664 and D66618 for some discussions. Reviewed By: bkramer, rsmith Differential Revision: https://reviews.llvm.org/D92297 Added: Modified: clang/lib/CodeGen/CGCall.cpp clang/test/CodeGenCXX/this-nonnull.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 78740018d416..2b9bfb6a6c88 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -2168,13 +2168,21 @@ void CodeGenModule::ConstructAttributeList( if (!CodeGenOpts.NullPointerIsValid && getContext().getTargetAddressSpace(FI.arg_begin()->type) == 0) { Attrs.addAttribute(llvm::Attribute::NonNull); + Attrs.addDereferenceableAttr( + getMinimumObjectSize( + FI.arg_begin()->type.castAs<PointerType>()->getPointeeType()) + .getQuantity()); + } else { + // FIXME dereferenceable should be correct here, regardless of + // NullPointerIsValid. However, dereferenceable currently does not always + // respect NullPointerIsValid and may imply nonnull and break the program. + // See https://reviews.llvm.org/D66618 for discussions. + Attrs.addDereferenceableOrNullAttr( + getMinimumObjectSize( + FI.arg_begin()->type.castAs<PointerType>()->getPointeeType()) + .getQuantity()); } - Attrs.addDereferenceableAttr( - getMinimumObjectSize( - FI.arg_begin()->type.castAs<PointerType>()->getPointeeType()) - .getQuantity()); - ArgAttrs[IRArgs.first] = llvm::AttributeSet::get(getLLVMContext(), Attrs); } diff --git a/clang/test/CodeGenCXX/this-nonnull.cpp b/clang/test/CodeGenCXX/this-nonnull.cpp index 9b074e2bdda1..63873388b070 100644 --- a/clang/test/CodeGenCXX/this-nonnull.cpp +++ b/clang/test/CodeGenCXX/this-nonnull.cpp @@ -12,8 +12,9 @@ void TestReturnsVoid(Struct &s) { s.ReturnsVoid(); // CHECK-YES: call void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* nonnull dereferenceable(12) %0) - // CHECK-NO: call void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* dereferenceable(12) %0) + /// FIXME Use dereferenceable after dereferenceable respects NullPointerIsValid. + // CHECK-NO: call void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* dereferenceable_or_null(12) %0) } // CHECK-YES: declare void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* nonnull dereferenceable(12)) -// CHECK-NO: declare void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* dereferenceable(12)) +// CHECK-NO: declare void @_ZN6Struct11ReturnsVoidEv(%struct.Struct* dereferenceable_or_null(12)) _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
