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
92 lines
3.4 KiB
C++
92 lines
3.4 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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#include "toolchain/check/cpp/location.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/Basic/SourceManager.h"
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#include "toolchain/sem_ir/absolute_node_ref.h"
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#include "toolchain/sem_ir/ids.h"
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namespace Carbon::Check {
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namespace {
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struct FileInfo {
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const SemIR::File* sem_ir;
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clang::SourceLocation start_loc;
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};
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} // namespace
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// Map a CheckIRId into information about the corresponding file in both SemIR
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// and Clang's source manager.
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static auto GetFileInfo(Context& context, SemIR::CheckIRId ir_id) -> FileInfo {
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const SemIR::File* sem_ir = &context.sem_ir();
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int file_index = 0;
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// If the file is imported, locate it in our imports map.
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if (ir_id != context.sem_ir().check_ir_id()) {
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auto import_id = context.check_ir_map().Get(ir_id);
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CARBON_CHECK(import_id.has_value());
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file_index = context.import_irs().GetRawIndex(import_id) + 1;
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sem_ir = context.import_irs().Get(import_id).sem_ir;
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CARBON_CHECK(sem_ir, "Node location in nonexistent IR");
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}
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// If we've seen this file before, reuse the same FileID.
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auto& file_start_locs = context.cpp_context()->carbon_file_locations();
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if (static_cast<int>(file_start_locs.size()) <= file_index) {
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// Never valid; prepare a slot for the caching below.
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file_start_locs.resize(file_index + 1);
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} else if (file_start_locs[file_index].isValid()) {
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return {.sem_ir = sem_ir, .start_loc = file_start_locs[file_index]};
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}
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// We've not seen this file before. Create a corresponding virtual file in
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// Clang's source manager.
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// TODO: Consider recreating the complete import path instead of only the
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// final entry.
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const auto& source = sem_ir->parse_tree().tokens().source();
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auto& src_mgr = context.ast_context().getSourceManager();
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auto file_id = src_mgr.createFileID(
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llvm::MemoryBufferRef(source.text(), source.filename()));
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auto file_start_loc = src_mgr.getLocForStartOfFile(file_id);
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file_start_locs[file_index] = file_start_loc;
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return {.sem_ir = sem_ir, .start_loc = file_start_loc};
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}
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auto GetCppLocation(Context& context, SemIR::LocId loc_id)
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-> clang::SourceLocation {
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if (!context.sem_ir().cpp_file()) {
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return clang::SourceLocation();
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}
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// Break down the `LocId` into an import path. If that ends in a C++ location,
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// we can just return that directly.
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llvm::SmallVector<SemIR::AbsoluteNodeRef> absolute_node_refs =
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SemIR::GetAbsoluteNodeRef(&context.sem_ir(), loc_id);
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const auto& final_node = absolute_node_refs.back();
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if (final_node.is_cpp()) {
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return final_node.file()->clang_source_locs().Get(
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final_node.clang_source_loc_id());
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}
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if (!final_node.node_id().has_value()) {
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// A non-existent NodeID implies our C++ is compiler-synthesised. Synthetic
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// code doesn't have a physical source location to retrieve, so the Clang
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// mapping is empty.
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return clang::SourceLocation();
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}
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// This is a location in Carbon code; get or create a corresponding file in
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// Clang and build a corresponding location.
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auto [ir, start_loc] = GetFileInfo(context, final_node.check_ir_id());
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const auto& tree = ir->parse_tree();
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auto offset =
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tree.tokens().GetByteOffset(tree.node_token(final_node.node_id()));
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return start_loc.getLocWithOffset(offset);
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}
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} // namespace Carbon::Check
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