2017-12-12 19:16:45 +08:00
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//===--- Context.cpp -----------------------------------------*- C++-*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===---------------------------------------------------------------------===//
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#include "Context.h"
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#include <cassert>
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namespace clang {
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namespace clangd {
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2018-02-25 15:21:16 +08:00
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Context Context::empty() { return Context(/*DataPtr=*/nullptr); }
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2017-12-12 19:16:45 +08:00
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Context::Context(std::shared_ptr<const Data> DataPtr)
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: DataPtr(std::move(DataPtr)) {}
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Context Context::clone() const { return Context(DataPtr); }
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2018-02-06 22:25:02 +08:00
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static Context ¤tContext() {
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static thread_local auto C = Context::empty();
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return C;
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}
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[clangd] Pass Context implicitly using TLS.
Summary:
Instead of passing Context explicitly around, we now have a thread-local
Context object `Context::current()` which is an implicit argument to
every function.
Most manipulation of this should use the WithContextValue helper, which
augments the current Context to add a single KV pair, and restores the
old context on destruction.
Advantages are:
- less boilerplate in functions that just propagate contexts
- reading most code doesn't require understanding context at all, and
using context as values in fewer places still
- fewer options to pass the "wrong" context when it changes within a
scope (e.g. when using Span)
- contexts pass through interfaces we can't modify, such as VFS
- propagating contexts across threads was slightly tricky (e.g.
copy vs move, no move-init in lambdas), and is now encapsulated in
the threadpool
Disadvantages are all the usual TLS stuff - hidden magic, and
potential for higher memory usage on threads that don't use the
context. (In practice, it's just one pointer)
Reviewers: ilya-biryukov
Subscribers: klimek, jkorous-apple, ioeric, cfe-commits
Differential Revision: https://reviews.llvm.org/D42517
llvm-svn: 323872
2018-01-31 21:40:48 +08:00
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const Context &Context::current() { return currentContext(); }
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Context Context::swapCurrent(Context Replacement) {
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std::swap(Replacement, currentContext());
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return Replacement;
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}
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2017-12-12 19:16:45 +08:00
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} // namespace clangd
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} // namespace clang
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