This reverts 4d10c1165442cbbbc0017b48fcdd7dae1ccf3678 and its two dependent commits: e6b9805b574bb5c90263ec7fbcb94df76d2807a4 and c243406a695ca056a07ef4064b0f9feee7685320, see discussion in https://github.com/llvm/llvm-project/pull/165598#issuecomment-3563825509.
MSVC supports an extension allowing to delete an array of objects via pointer whose static type doesn't match its dynamic type. This is done via generation of special destructors - vector deleting destructors. MSVC's virtual tables always contain a pointer to the vector deleting destructor for classes with virtual destructors, so not having this extension implemented causes clang to generate code that is not compatible with the code generated by MSVC, because clang always puts a pointer to a scalar deleting destructor to the vtable. As a bonus the deletion of an array of polymorphic object will work just like it does with MSVC - no memory leaks and correct destructors are called. This patch will cause clang to emit code that is compatible with code produced by MSVC but not compatible with code produced with clang of older versions, so the new behavior can be disabled via passing -fclang-abi-compat=21 (or lower). This is yet another attempt to land vector deleting destructors support originally implemented by https://github.com/llvm/llvm-project/pull/133451. This PR contains fixes for issues reported in the original PR as well as fixes for issues related to operator delete[] search reported in several issues like https://github.com/llvm/llvm-project/pull/133950#issuecomment-2787510484 https://github.com/llvm/llvm-project/issues/134265 Fixes https://github.com/llvm/llvm-project/issues/19772
This changes a bunch of places which use getAs<TagType>, including derived types, just to obtain the tag definition. This is preparation for #155028, offloading all the changes that PR used to introduce which don't depend on any new helpers.
This is a major change on how we represent nested name qualifications in the AST. * The nested name specifier itself and how it's stored is changed. The prefixes for types are handled within the type hierarchy, which makes canonicalization for them super cheap, no memory allocation required. Also translating a type into nested name specifier form becomes a no-op. An identifier is stored as a DependentNameType. The nested name specifier gains a lightweight handle class, to be used instead of passing around pointers, which is similar to what is implemented for TemplateName. There is still one free bit available, and this handle can be used within a PointerUnion and PointerIntPair, which should keep bit-packing aficionados happy. * The ElaboratedType node is removed, all type nodes in which it could previously apply to can now store the elaborated keyword and name qualifier, tail allocating when present. * TagTypes can now point to the exact declaration found when producing these, as opposed to the previous situation of there only existing one TagType per entity. This increases the amount of type sugar retained, and can have several applications, for example in tracking module ownership, and other tools which care about source file origins, such as IWYU. These TagTypes are lazily allocated, in order to limit the increase in AST size. This patch offers a great performance benefit. It greatly improves compilation time for [stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for `test_on2.cpp` in that project, which is the slowest compiling test, this patch improves `-c` compilation time by about 7.2%, with the `-fsyntax-only` improvement being at ~12%. This has great results on compile-time-tracker as well:  This patch also further enables other optimziations in the future, and will reduce the performance impact of template specialization resugaring when that lands. It has some other miscelaneous drive-by fixes. About the review: Yes the patch is huge, sorry about that. Part of the reason is that I started by the nested name specifier part, before the ElaboratedType part, but that had a huge performance downside, as ElaboratedType is a big performance hog. I didn't have the steam to go back and change the patch after the fact. There is also a lot of internal API changes, and it made sense to remove ElaboratedType in one go, versus removing it from one type at a time, as that would present much more churn to the users. Also, the nested name specifier having a different API avoids missing changes related to how prefixes work now, which could make existing code compile but not work. How to review: The important changes are all in `clang/include/clang/AST` and `clang/lib/AST`, with also important changes in `clang/lib/Sema/TreeTransform.h`. The rest and bulk of the changes are mostly consequences of the changes in API. PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just for easier to rebasing. I plan to rename it back after this lands. Fixes #136624 Fixes https://github.com/llvm/llvm-project/issues/43179 Fixes https://github.com/llvm/llvm-project/issues/68670 Fixes https://github.com/llvm/llvm-project/issues/92757
Finding operator delete[] is still problematic, without it the extension is a security hazard, so reverting until the problem with operator delete[] is figured out. This reverts the following PRs: Reland [MS][clang] Add support for vector deleting destructors (llvm#133451) [MS][clang] Make sure vector deleting dtor calls correct operator delete (llvm#133950) [MS][clang] Fix crash on deletion of array of pointers (llvm#134088) [clang] Do not diagnose unused deleted operator delete[] (llvm#134357) [MS][clang] Error about ambiguous operator delete[] only when required (llvm#135041)
See also https://github.com/llvm/llvm-project/pull/130734 for the original motivation. This pattern (`container_of`) is also widely used by real-world programs. Examples: https://github.com/llvm/llvm-project/blob/1d89d7d5d76e391b035f50343e2a4890506c6f2b/llvm/include/llvm/IR/SymbolTableListTraits.h#L77-L87 https://github.com/nodejs/node/blob/a2a53cb728ec5f776ac16879ce0f480a8e838320/src/util-inl.h#L134-L137 https://github.com/search?q=*%29nullptr-%3E*&type=code
Whereas it is UB in terms of the standard to delete an array of objects via pointer whose static type doesn't match its dynamic type, MSVC supports an extension allowing to do it. Aside from array deletion not working correctly in the mentioned case, currently not having this extension implemented causes clang to generate code that is not compatible with the code generated by MSVC, because clang always puts scalar deleting destructor to the vftable. This PR aims to resolve these problems. It was reverted due to link time errors in chromium with sanitizer coverage enabled, which is fixed by https://github.com/llvm/llvm-project/pull/131929 . The second commit of this PR also contains a fix for a runtime failure in chromium reported in https://github.com/llvm/llvm-project/pull/126240#issuecomment-2730216384 . Fixes https://github.com/llvm/llvm-project/issues/19772
Original PR: #130537
Originally reverted due to revert of dependent commit. Relanding with no
changes.
This changes the MemberPointerType representation to use a
NestedNameSpecifier instead of a Type to represent the base class.
Since the qualifiers are always parsed as nested names, there was an
impedance mismatch when converting these back and forth into types, and
this led to issues in preserving sugar.
The nested names are indeed a better match for these, as the differences
which a QualType can represent cannot be expressed syntatically, and
they represent the use case more exactly, being either dependent or
referring to a CXXRecord, unqualified.
This patch also makes the MemberPointerType able to represent sugar for
a {up/downcast}cast conversion of the base class, although for now the
underlying type is canonical, as preserving the sugar up to that point
requires further work.
As usual, includes a few drive-by fixes in order to make use of the
improvements.
Relands Original PR: https://github.com/llvm/llvm-project/pull/131965
Addresses
https://github.com/llvm/llvm-project/pull/131965#issuecomment-2741619498
* Fixes isIncompleteType for injected classes
This clears up some uses of getClass on MemberPointerType when
equivalent uses of getMostRecentCXXRecordDecl would be just as simple or
simpler.
This is split-off from a larger patch which removes getClass, in order
to facilitate review.
Reverts llvm/llvm-project#131965 Reverted due to issue reported here: https://github.com/llvm/llvm-project/pull/131965#issuecomment-2741619498