forked from OSchip/llvm-project
121 lines
5.0 KiB
C++
121 lines
5.0 KiB
C++
//===--- Preamble.h - Reusing expensive parts of the AST ---------*- C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// The vast majority of code in a typical translation unit is in the headers
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// included at the top of the file.
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//
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// The preamble optimization says that we can parse this code once, and reuse
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// the result multiple times. The preamble is invalidated by changes to the
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// code in the preamble region, to the compile command, or to files on disk.
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//
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// This is the most important optimization in clangd: it allows operations like
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// code-completion to have sub-second latency. It is supported by the
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// PrecompiledPreamble functionality in clang, which wraps the techniques used
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// by PCH files, modules etc into a convenient interface.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_PREAMBLE_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_PREAMBLE_H
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#include "CollectMacros.h"
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#include "Compiler.h"
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#include "Diagnostics.h"
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#include "FS.h"
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#include "Headers.h"
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#include "index/CanonicalIncludes.h"
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#include "support/Path.h"
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#include "clang/Frontend/CompilerInvocation.h"
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#include "clang/Frontend/PrecompiledPreamble.h"
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#include "clang/Tooling/CompilationDatabase.h"
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#include "llvm/ADT/StringRef.h"
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#include <memory>
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#include <string>
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#include <vector>
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namespace clang {
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namespace clangd {
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/// The parsed preamble and associated data.
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///
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/// As we must avoid re-parsing the preamble, any information that can only
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/// be obtained during parsing must be eagerly captured and stored here.
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struct PreambleData {
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PreambleData(const ParseInputs &Inputs, PrecompiledPreamble Preamble,
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std::vector<Diag> Diags, IncludeStructure Includes,
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MainFileMacros Macros,
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std::unique_ptr<PreambleFileStatusCache> StatCache,
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CanonicalIncludes CanonIncludes);
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// Version of the ParseInputs this preamble was built from.
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std::string Version;
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tooling::CompileCommand CompileCommand;
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PrecompiledPreamble Preamble;
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std::vector<Diag> Diags;
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// Processes like code completions and go-to-definitions will need #include
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// information, and their compile action skips preamble range.
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IncludeStructure Includes;
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// Macros defined in the preamble section of the main file.
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// Users care about headers vs main-file, not preamble vs non-preamble.
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// These should be treated as main-file entities e.g. for code completion.
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MainFileMacros Macros;
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// Cache of FS operations performed when building the preamble.
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// When reusing a preamble, this cache can be consumed to save IO.
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std::unique_ptr<PreambleFileStatusCache> StatCache;
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CanonicalIncludes CanonIncludes;
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};
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using PreambleParsedCallback =
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std::function<void(ASTContext &, std::shared_ptr<clang::Preprocessor>,
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const CanonicalIncludes &)>;
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/// Build a preamble for the new inputs unless an old one can be reused.
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/// If \p PreambleCallback is set, it will be run on top of the AST while
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/// building the preamble.
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std::shared_ptr<const PreambleData>
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buildPreamble(PathRef FileName, CompilerInvocation CI,
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const ParseInputs &Inputs, bool StoreInMemory,
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PreambleParsedCallback PreambleCallback);
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/// Returns true if \p Preamble is reusable for \p Inputs. Note that it will
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/// return true when some missing headers are now available.
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/// FIXME: Should return more information about the delta between \p Preamble
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/// and \p Inputs, e.g. new headers.
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bool isPreambleCompatible(const PreambleData &Preamble,
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const ParseInputs &Inputs, PathRef FileName,
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const CompilerInvocation &CI);
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/// Stores information required to parse a TU using a (possibly stale) Baseline
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/// preamble. Updates compiler invocation to approximately reflect additions to
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/// the preamble section of Modified contents, e.g. new include directives.
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class PreamblePatch {
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public:
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// With an empty patch, the preamble is used verbatim.
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PreamblePatch() = default;
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/// Builds a patch that contains new PP directives introduced to the preamble
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/// section of \p Modified compared to \p Baseline.
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/// FIXME: This only handles include directives, we should at least handle
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/// define/undef.
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static PreamblePatch create(llvm::StringRef FileName,
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const ParseInputs &Modified,
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const PreambleData &Baseline);
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/// Adjusts CI (which compiles the modified inputs) to be used with the
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/// baseline preamble. This is done by inserting an artifical include to the
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/// \p CI that contains new directives calculated in create.
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void apply(CompilerInvocation &CI) const;
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private:
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std::string PatchContents;
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std::string PatchFileName;
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};
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} // namespace clangd
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} // namespace clang
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#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_PREAMBLE_H
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