mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 22:02:23 +01:00
Chandler Carruth
7901fb3857
Fundamentally, this uses forward declarations of Clang types to reduce the overall compile time cost of Clang headers across the codebase. Tracing and profiling showed ~2s of every check TU's ~8-12s compile time going just to parsing Clang frontend and AST headers pulled in via a few sem_ir and check headers that only use the Clang types by pointer or reference: - sem_ir/cpp_file.h (reached via sem_ir/file.h by ~150 TUs) included clang/Frontend/CompilerInstance.h, clang/CodeGen/ModuleBuilder.h, clang/AST/Mangle.h, and llvm/IR/Module.h. CppFile's accessors move out of line to a new cpp_file.cpp and the header now forward-declares the Clang types. - check/cpp/context.h (reached via check/context.h by ~100 TUs) included clang/Frontend/FrontendAction.h and clang/Parse/Parser.h, pulling in clang's Sema.h and ASTUnit.h. - sem_ir/clang_decl.h included clang/AST/Decl.h; the three small functions that need complete Clang types move out of line. - sem_ir/cpp_overload_set.h included clang/Sema/Overload.h solely for the three-field OverloadCandidateSet::OperatorRewriteInfo, which is now mirrored as CppOverloadSet::OperatorRewriteInfo, and clang/AST/Decl.h solely for a pointer. - sem_ir/name_scope.h's clang/AST/DeclBase.h include was vestigial. TUs (and more narrowly included headers) that genuinely use the Clang definitions now include the Clang headers directly. Representative compile times (fastbuild, aarch64), combined with the preceding instantiation-cost changes, relative to trunk: - check/eval.cpp: 11.85s -> 6.94s (-41%) - check/handle_operator.cpp: 7.71s -> 3.30s (-57%) - language_server.cpp: 6.68s -> 3.16s (-53%) - lower/handle.cpp: 6.75s -> 3.66s (-46%) - sem_ir/file.cpp: 8.60s -> 6.11s (-29%) - driver.cpp: 6.68s -> 4.78s (-28%) Measured full-rebuild impact (316 first-party TUs, fastbuild): -689.5s CPU, -29.9% relative to trunk. Assisted-by: Claude
77 lines
2.2 KiB
C++
77 lines
2.2 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#ifndef CARBON_TOOLCHAIN_CHECK_CPP_CONTEXT_H_
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#define CARBON_TOOLCHAIN_CHECK_CPP_CONTEXT_H_
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#include <memory>
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#include "clang/Basic/SourceLocation.h"
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#include "common/check.h"
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#include "llvm/ADT/SmallVector.h"
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namespace clang {
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class ASTContext;
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class CompilerInstance;
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class FunctionDecl;
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class MangleContext;
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class Parser;
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class Sema;
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} // namespace clang
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namespace Carbon::Check {
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// Context for C++ code during check.
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//
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// This stores state for a Clang AST and Sema, as well as any additional
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// information needed to perform mapping between Carbon and C++ types,
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// declarations, and similar values.
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class CppContext {
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public:
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explicit CppContext(clang::CompilerInstance& instance,
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std::unique_ptr<clang::Parser> parser);
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~CppContext();
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auto ast_context() -> clang::ASTContext& { return *ast_context_; }
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auto sema() -> clang::Sema& { return *sema_; }
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auto parser() -> clang::Parser& { return *parser_; }
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auto clang_mangle_context() -> clang::MangleContext&;
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auto carbon_file_locations() -> llvm::SmallVector<clang::SourceLocation>& {
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return carbon_file_locations_;
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}
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auto placement_new_decl() const -> clang::FunctionDecl* {
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return placement_new_decl_;
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}
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void set_placement_new_decl(clang::FunctionDecl* decl) {
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placement_new_decl_ = decl;
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}
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private:
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// The Clang AST context.
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clang::ASTContext* ast_context_;
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// The Clang semantic analysis engine.
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clang::Sema* sema_;
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// The Clang parser.
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std::unique_ptr<clang::Parser> parser_;
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// Per-Carbon-file start locations for corresponding Clang source buffers.
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// Owned and managed by code in location.cpp.
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llvm::SmallVector<clang::SourceLocation> carbon_file_locations_;
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// The Clang mangle context for the target in the ASTContext.
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std::unique_ptr<clang::MangleContext> clang_mangle_context_;
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// The cached placement new function declaration.
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clang::FunctionDecl* placement_new_decl_ = nullptr;
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};
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} // namespace Carbon::Check
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#endif // CARBON_TOOLCHAIN_CHECK_CPP_CONTEXT_H_
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