forked from OSchip/llvm-project
0cb7e7ca0c
The idiom:
```
DeclContext::lookup_result R = DeclContext::lookup(Name);
for (auto *D : R) {...}
```
is not safe when in the loop body we trigger deserialization from an AST file.
The deserialization can insert new declarations in the StoredDeclsList whose
underlying type is a vector. When the vector decides to reallocate its storage
the pointer we hold becomes invalid.
This patch replaces a SmallVector with an singly-linked list. The current
approach stores a SmallVector<NamedDecl*, 4> which is around 8 pointers.
The linked list is 3, 5, or 7. We do better in terms of memory usage for small
cases (and worse in terms of locality -- the linked list entries won't be near
each other, but will be near their corresponding declarations, and we were going
to fetch those memory pages anyway). For larger cases: the vector uses a
doubling strategy for reallocation, so will generally be between half-full and
full. Let's say it's 75% full on average, so there's N * 4/3 + 4 pointers' worth
of space allocated currently and will be 2N pointers with the linked list. So we
break even when there are N=6 entries and slightly lose in terms of memory usage
after that. We suspect that's still a win on average.
Thanks to @rsmith!
Differential revision: https://reviews.llvm.org/D91524
|
||
|---|---|---|
| .. | ||
| clang-apply-replacements | ||
| clang-change-namespace | ||
| clang-doc | ||
| clang-include-fixer | ||
| clang-move | ||
| clang-query | ||
| clang-reorder-fields | ||
| clang-tidy | ||
| clangd | ||
| docs | ||
| modularize | ||
| pp-trace | ||
| test | ||
| tool-template | ||
| unittests | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| LICENSE.TXT | ||
| README.txt | ||
README.txt
//===----------------------------------------------------------------------===// // Clang Tools repository //===----------------------------------------------------------------------===// Welcome to the repository of extra Clang Tools. This repository holds tools that are developed as part of the LLVM compiler infrastructure project and the Clang frontend. These tools are kept in a separate "extra" repository to allow lighter weight checkouts of the core Clang codebase. This repository is only intended to be checked out inside of a full LLVM+Clang tree, and in the 'tools/extra' subdirectory of the Clang checkout. All discussion regarding Clang, Clang-based tools, and code in this repository should be held using the standard Clang mailing lists: http://lists.llvm.org/mailman/listinfo/cfe-dev Code review for this tree should take place on the standard Clang patch and commit lists: http://lists.llvm.org/mailman/listinfo/cfe-commits If you find a bug in these tools, please file it in the LLVM bug tracker: http://llvm.org/bugs/