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David BlaikieandRichard Smith
dfed743de2
A small step to virtual functions - adding vtable pointers to the
layout, but not initializing or otherwise using them at this stage.
A few open design questions I'd love feedback on:
* Is this the right/good enough SemIR representation for now? This patch
adds a `is_dynamic` attribute to `SemIR::Class` and populates/flags it
based on the flag of the base class, or if any virtual function is
declared in the class (or, at least that's my intent). Some other
options include:
* Each `Class` could store a `ClassId` (or `TypeId`?) of the (possibly
indirect, possibly self) base class that is the first one that is
dynamic/has a vtable pointer
* Could make the property narrower, like `has vtable pointer` and have
it `true` only on the type that introduces the vtable - then derived
classes would have to walk their base classes to check if they're the
one that needs to define the vtable pointer or not
* Should the vtable be the first element in the type? If there's a
non-dynamic base type, we could have a layout that's `{<non-dynamic base
type>, vtable ptr, <derived members>}`? Derived types would still be
able to uniquely identify where their vtable pointer is just fine... -
and the vtable pointer is, in a sense, a member of that intermediate
type, so it does seem a bit strange to force it to the front - but I
guess it's probably more efficient in some ways?
Open to any other suggestions/advice/thoughts on the direction, etc.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
55 lines
1.8 KiB
C++
55 lines
1.8 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/name.h"
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#include "llvm/ADT/StringSwitch.h"
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namespace Carbon::SemIR {
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// Get the spelling to use for a special name.
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static auto GetSpecialName(NameId name_id, bool for_ir) -> llvm::StringRef {
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switch (name_id.index) {
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case NameId::Invalid.index:
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return for_ir ? "" : "<invalid>";
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case NameId::SelfValue.index:
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return "self";
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case NameId::SelfType.index:
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return "Self";
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case NameId::PeriodSelf.index:
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return ".Self";
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case NameId::ReturnSlot.index:
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return for_ir ? "return" : "<return slot>";
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case NameId::PackageNamespace.index:
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return "package";
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case NameId::Base.index:
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return "base";
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case NameId::Vptr.index:
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return for_ir ? "vptr" : "<vptr>";
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default:
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CARBON_FATAL("Unknown special name");
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}
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}
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auto NameStoreWrapper::GetFormatted(NameId name_id) const -> llvm::StringRef {
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// If the name is an identifier name with a keyword spelling, format it with
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// an `r#` prefix. Format any other identifier name as just the identifier.
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if (auto string_name = GetAsStringIfIdentifier(name_id)) {
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return llvm::StringSwitch<llvm::StringRef>(*string_name)
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#define CARBON_KEYWORD_TOKEN(Name, Spelling) .Case(Spelling, "r#" Spelling)
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#include "toolchain/lex/token_kind.def"
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.Default(*string_name);
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}
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return GetSpecialName(name_id, /*for_ir=*/false);
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}
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auto NameStoreWrapper::GetIRBaseName(NameId name_id) const -> llvm::StringRef {
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if (auto string_name = GetAsStringIfIdentifier(name_id)) {
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return *string_name;
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}
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return GetSpecialName(name_id, /*for_ir=*/true);
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}
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} // namespace Carbon::SemIR
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