[clang] Improve nested name specifier AST representation #147835
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Patch series starting at #147835
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Patch series starting at #147835
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My game plan for merging this PR is to merge all the other PRs into this branch, collapsing everything into a single PR again. Let me know if you have better ideas. |
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 #147000
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This contains the NestedNameSpecifier representation changes originally from: #147835
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clang test changes Third patch in the series, starting at #147835
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The HLSL Tests bot failure was some GitHub permission issue when publishing the results of the successful run: |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/200/builds/14983 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/162/builds/28595 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/22354 Here is the relevant piece of the build log for the reference |
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This completes #147835 by adapting the changes in the API to the rewriter. Fixes build failures such as reported here: #147835 (comment) We previously missed this because it was not tested in pre-commit CI. This patch also addresses that problem.
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This completes #147835 by adapting the changes in the API to the rewriter. Fixes build failures such as reported here: #147835 (comment) We previously missed this because it was not tested in pre-commit CI.
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This completes #147835 by adapting the changes in the API to the rewriter. Fixes build failures such as reported here: #147835 (comment) We previously missed this because it was not tested in pre-commit CI.
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This completes llvm/llvm-project#147835 by adapting the changes in the API to the rewriter. Fixes build failures such as reported here: llvm/llvm-project#147835 (comment) We previously missed this because it was not tested in pre-commit CI.
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…m#147835)" needs dependent PR [clang][CGRecordLayout] Remove dependency on isZeroSize (llvm#96422) This reverts commit 91cdd35.
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This is a major change on how we represent nested name qualifications in the AST.
This patch offers a great performance benefit.
It greatly improves compilation time for stdexec. For one datapoint, for
test_on2.cppin that project, which is the slowest compiling test, this patch improves-ccompilation time by about 7.2%, with the-fsyntax-onlyimprovement 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/ASTandclang/lib/AST, with also important changes inclang/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
getOriginalDeclin this patch, just for easier to rebasing. I plan to rename it back after this lands.Fixes #136624
Fixes #43179
Fixes #68670
Fixes #92757