[AST] Split parent map traversal logic into ParentMapContext.h
authorReid Kleckner <rnk@google.com>
Tue, 10 Dec 2019 01:03:47 +0000 (17:03 -0800)
committerReid Kleckner <rnk@google.com>
Fri, 24 Jan 2020 21:42:28 +0000 (13:42 -0800)
commit8a81daaa8b58aeaa192a47c4ce7f94b4d59ce082
tree266495be64752b68180e6050b84f1ac13ac354c2
parentb1f3a0f972f60587f8bd689442f0c71a78273c8d
[AST] Split parent map traversal logic into ParentMapContext.h

The only part of ASTContext.h that requires most AST types to be
complete is the parent map. Nothing in Clang proper uses the ParentMap,
so split it out into its own class. Make ASTContext own the
ParentMapContext so there is still a one-to-one relationship.

After this change, 562 fewer files depend on ASTTypeTraits.h, and 66
fewer depend on TypeLoc.h:
  $ diff -u deps-before.txt deps-after.txt | \
    grep '^[-+] ' | sort | uniq -c | sort -nr | less
      562 -    ../clang/include/clang/AST/ASTTypeTraits.h
      340 +    ../clang/include/clang/AST/ParentMapContext.h
       66 -    ../clang/include/clang/AST/TypeLocNodes.def
       66 -    ../clang/include/clang/AST/TypeLoc.h
       15 -    ../clang/include/clang/AST/TemplateBase.h
  ...
I computed deps-before.txt and deps-after.txt with `ninja -t deps`.

This removes a common and key dependency on TemplateBase.h and
TypeLoc.h.

This also has the effect of breaking the ParentMap RecursiveASTVisitor
instantiation into its own file, which roughly halves the compilation
time of ASTContext.cpp (29.75s -> 17.66s). The new file takes 13.8s to
compile.

I left behind forwarding methods for getParents(), but clients will need
to include a new header to make them work:
  #include "clang/AST/ParentMapContext.h"

I noticed that this parent map functionality is unfortunately duplicated
in ParentMap.h, which only works for Stmt nodes.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D71313
18 files changed:
clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
clang-tools-extra/clang-tidy/readability/MakeMemberFunctionConstCheck.cpp
clang-tools-extra/clang-tidy/utils/ExprSequence.cpp
clang/include/clang/AST/ASTContext.h
clang/include/clang/AST/ASTNodeTraverser.h
clang/include/clang/AST/ParentMapContext.h [new file with mode: 0644]
clang/include/clang/ASTMatchers/ASTMatchers.h
clang/include/clang/Sema/Sema.h
clang/lib/AST/ASTContext.cpp
clang/lib/AST/CMakeLists.txt
clang/lib/AST/Linkage.h
clang/lib/AST/ParentMapContext.cpp [new file with mode: 0644]
clang/lib/ASTMatchers/ASTMatchFinder.cpp
clang/lib/ASTMatchers/ASTMatchersInternal.cpp
clang/lib/CodeGen/CGCall.h
clang/lib/Tooling/ASTDiff/ASTDiff.cpp
clang/lib/Tooling/Refactoring/Rename/USRLocFinder.cpp
lldb/include/lldb/Symbol/TypeSystemClang.h