mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-10-01 20:55:58 +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
82 lines
3.2 KiB
C++
82 lines
3.2 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_EXPORT_H_
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#define CARBON_TOOLCHAIN_CHECK_CPP_EXPORT_H_
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#include "clang/AST/Decl.h"
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#include "toolchain/check/context.h"
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#include "toolchain/sem_ir/ids.h"
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namespace clang {
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class CXXDestructorDecl;
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class CXXRecordDecl;
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} // namespace clang
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namespace Carbon::Check {
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// Exports a Carbon name scope into C++ as a namespace or class, or returns the
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// C++ namespace or class declaration that it was imported from.
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//
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// If the name scope has already been exported, returns the existing context.
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// Otherwise, creates a new C++ declaration context and returns it. Returns
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// nullptr if the name scope could not be exported and an error was diagnosed.
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auto ExportNameScopeToCpp(Context& context, SemIR::LocId loc_id,
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SemIR::NameScopeId name_scope_id)
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-> clang::DeclContext*;
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// Exports a Carbon class into C++ as a class, or returns the C++ tag type that
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// the class was imported from.
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//
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// If the class has already been exported, returns the existing C++ class.
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// Otherwise, creates a new C++ class and returns it. Returns nullptr if the
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// class could not be exported and an error was diagnosed.
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auto ExportClassToCpp(Context& context, SemIR::LocId loc_id,
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SemIR::ClassType class_type) -> clang::TagDecl*;
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// Export all `SemIR::FieldDecl`s in the class body as `clang::FieldDecl`s.
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auto ExportAllFieldsToCpp(Context& context, SemIR::Class& class_info) -> void;
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// Exports a Carbon class field into C++.
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//
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// If the field has already been exported, returns the existing C++
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// field.
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//
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// If the field has not already been exported, *all* fields of the class
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// are exported, and then the requested C++ field is returned.
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//
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// Returns nullptr if the class could not be exported and an error was
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// diagnosed.
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auto ExportFieldToCpp(Context& context, SemIR::InstId field_inst_id,
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SemIR::FieldDecl field_decl) -> clang::FieldDecl*;
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// Get the field offset for each field in a class.
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//
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// Returns true on success, false if any error occurs.
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auto CalculateCppFieldOffsets(
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Context& context, SemIR::ClassId class_id,
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llvm::DenseMap<const clang::FieldDecl*, uint64_t>& field_offsets) -> bool;
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// Get a `clang::FunctionDecl` that can be used to call a Carbon function.
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auto ExportFunctionToCpp(Context& context, SemIR::LocId loc_id,
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SemIR::FunctionId function_id) -> clang::FunctionDecl*;
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// Export a Carbon destructor into C++.
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//
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// The destructor calls the `Destroy` operator.
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auto ExportDestructorToCpp(Context& context, const SemIR::Class& class_info,
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clang::CXXRecordDecl* record_decl)
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-> clang::CXXDestructorDecl*;
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// Export a Carbon variable into C++.
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//
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// Returns nullptr if the variable could not be exported an an error was
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// diagnosed.
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auto ExportVarToCpp(Context& context, SemIR::InstId inst_id,
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SemIR::VarStorage var_storage) -> clang::VarDecl*;
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} // namespace Carbon::Check
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#endif // CARBON_TOOLCHAIN_CHECK_CPP_EXPORT_H_
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