mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 21:10:12 +01:00
Nicholas Bishop
f2c94517cc
In generate_ast.cpp, an `CarbonExternalASTSource` is installed that has a `Check::Context` pointer. During lowering, this `ExternalASTSource` is still installed, and using it can cause a crash if the now-invalid pointer is dereferenced. Fix by adding a new `ReadOnlyASTSource` in sem_ir, and using that during lowering. `CarbonExternalASTSource` now inherits from `ReadOnlyASTSource` to avoid some code duplication. In generate_ast.cpp, we now always install a multiplex source, even if there's only one child source. Clang internally keeps pointers to the top-level `ExternalASTSource` installed via `setExternalSource`, and those pointers aren't updated if `setExternalSource` is called again. By using `MultiplexExternalSemaSource`, we can keep the top-level `ExternalASTSource` pointer the same, and only update its children. Using `MultiplexExternalSemaSource` this way requires a new constructor and a method to modify its child sources; added a new LLVM patch adding those. Originally landed in #7335, reverted in #7353 due to ASAN errors. Changes since original: * Use LLVM RTTI to make `Lower::Context::Finalize` less brittle. Add LLVM RTTI to `ReadOnlyASTSource` (and `CarbonExternalASTSource`). Change Finalize so that instead of just deleting the last multiplex child source, it erases any multiplex child sources that match `ReadOnlyASTSource`; this includes `CarbonExternalASTSource` since it's a subclass. * Fix ASAN error by updating the `MultiplexExternalSemaSource` earlier in lowering. It is sometimes accessed during PrepareToLower, so update it in `Context::GetFileContext` rather than `Context::Finalize`. Fixes https://github.com/carbon-language/carbon-lang/issues/7142
94 lines
3.4 KiB
C++
94 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/sem_ir/read_only_ast_source.h"
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namespace Carbon::SemIR {
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char ReadOnlyASTSource::id;
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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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static auto CalculateCppFieldOffsets(
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const File& sem_ir, SemIR::ClassId class_id,
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llvm::DenseMap<const clang::FieldDecl*, uint64_t>& field_offsets) -> bool {
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auto class_info = sem_ir.classes().Get(class_id);
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const auto& class_scope = sem_ir.name_scopes().Get(class_info.scope_id);
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auto class_layout = SemIR::ObjectLayout::Empty();
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for (const auto& struct_field : class_info.GetStructTypeFields(sem_ir)) {
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auto field_type_id =
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sem_ir.types().GetTypeIdForTypeInstId(struct_field.type_inst_id);
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auto field_layout =
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sem_ir.types().GetCompleteTypeInfo(field_type_id).object_layout;
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// Use the field's name to look up the corresponding entry in the
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// class. If it's a `FieldDecl`, write out the offset of the
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// corresponding `clang::FieldDecl`.
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auto class_field =
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LookupClassFieldByStructField(sem_ir, class_scope, struct_field);
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if (class_field) {
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const auto* clang_decl =
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sem_ir.clang_decls().Lookup(class_field->inst_id);
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if (!clang_decl) {
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return false;
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}
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auto* cpp_field_decl = cast<clang::FieldDecl>(clang_decl->decl());
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field_offsets.insert(
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{cpp_field_decl, class_layout.FieldOffset(field_layout).bits()});
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}
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class_layout.AppendField(field_layout);
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}
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return true;
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}
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auto ReadOnlyASTSource::layoutRecordType(
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const clang::RecordDecl* record_decl, uint64_t& size, uint64_t& alignment,
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llvm::DenseMap<const clang::FieldDecl*, uint64_t>& field_offsets,
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llvm::DenseMap<const clang::CXXRecordDecl*, clang::CharUnits>& base_offsets,
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llvm::DenseMap<const clang::CXXRecordDecl*, clang::CharUnits>&
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vbase_offsets) -> bool {
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auto carbon_class_info = GetAsCarbonOwnedClass(sem_ir_, record_decl);
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if (!carbon_class_info) {
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return false;
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}
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auto& [class_type_id, class_type] = *carbon_class_info;
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// Set the overall size and alignment. We round up the size to an integer
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// number of bytes in order to avoid surprising Clang too much.
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auto layout =
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sem_ir_.types().GetCompleteTypeInfo(class_type_id).object_layout;
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size = layout.size.bytes() * 8;
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alignment = layout.alignment.bits();
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// Fill in `field_offsets`.
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CalculateCppFieldOffsets(sem_ir_, class_type.class_id, field_offsets);
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// Add offset for base class, if any.
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if (const auto* class_decl = dyn_cast<clang::CXXRecordDecl>(record_decl);
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class_decl && !class_decl->bases().empty()) {
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CARBON_CHECK(class_decl->getNumBases() == 1,
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"Carbon class with multiple bases");
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const auto& base = *class_decl->bases_begin();
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// TODO: If this class introduced a vptr, the base will be at an offset of
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// `sizeof(void*)`, not 0.
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base_offsets.insert(
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{base.getType()->getAsCXXRecordDecl()->getCanonicalDecl(),
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clang::CharUnits::Zero()});
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// TODO: Support deriving from a C++ class with virtual bases.
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CARBON_CHECK(class_decl->getNumVBases() == 0,
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"Carbon class with multiple bases");
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static_cast<void>(vbase_offsets);
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}
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return true;
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}
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} // namespace Carbon::SemIR
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