mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 20:10:13 +01:00
Adrien Leravat
19c74ead49
Add partial support for initializing expressions for variable declaration. This is based on https://github.com/carbon-language/carbon-lang/pull/2006, which introduces expression categories, and how it is possible to convert to/from those different categories. ## Functional changes * Initializing expressions initialize directly the provided storage when used to initialize a variable. * Allows initializing expressions to avoid a copy when using `[var|let] name: type = call_expression(...)` by initializing `name` in-place. * Support `returned var: ...` and `return <expr>` * Support nested initializing expressions ## Main implementation changes * Updated PatternMatch logic to handle expression categories * Updated `VariableDefinition` interpreter statement to allocate and pass a location to initializing expressions * Update statement actions to allow passing an allocation, used by return expr or returned var * Modified the RuntimeScope API to be one step closer to the memory model we want to have * Remove `GetAllocationId` and older `Bind` which don't apply * New set of tests to highlight those different situations * Added a new intrinsic to print the allocation stack (and make sure we behave correctly, beyond visible side effects) ## Next work * Dedicated `Action` to retrieve expression category information in the interpreter (https://github.com/carbon-language/carbon-lang/pull/2927) * Avoid copies when initializing value expression from reference expression and prevent mutations for the duration of the "pinning" (https://github.com/carbon-language/carbon-lang/pull/2927) * Avoid unnecessary copies from value expression to value expression, after ensuring that even value expression temporaries are registered for destruction. * Avoid unnecessary copies when binding function arguments
115 lines
3.9 KiB
C++
115 lines
3.9 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 "explorer/interpreter/heap.h"
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#include "common/check.h"
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#include "explorer/ast/value.h"
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#include "explorer/common/error_builders.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/Error.h"
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namespace Carbon {
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auto Heap::AllocateValue(Nonnull<const Value*> v) -> AllocationId {
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// Putting the following two side effects together in this function
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// ensures that we don't do anything else in between, which would be really
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// bad! Consider whether to include a copy of the input v in this function or
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// to leave it up to the caller.
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AllocationId a(values_.size());
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values_.push_back(v);
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if (v->kind() == Carbon::Value::Kind::UninitializedValue) {
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states_.push_back(ValueState::Uninitialized);
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} else {
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states_.push_back(ValueState::Alive);
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}
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return a;
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}
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auto Heap::Read(const Address& a, SourceLocation source_loc) const
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-> ErrorOr<Nonnull<const Value*>> {
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CARBON_RETURN_IF_ERROR(this->CheckInit(a.allocation_, source_loc));
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CARBON_RETURN_IF_ERROR(this->CheckAlive(a.allocation_, source_loc));
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Nonnull<const Value*> value = values_[a.allocation_.index_];
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return value->GetElement(arena_, a.element_path_, source_loc, value);
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}
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auto Heap::Write(const Address& a, Nonnull<const Value*> v,
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SourceLocation source_loc) -> ErrorOr<Success> {
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CARBON_RETURN_IF_ERROR(this->CheckAlive(a.allocation_, source_loc));
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if (states_[a.allocation_.index_] == ValueState::Uninitialized) {
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if (!a.element_path_.IsEmpty()) {
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return ProgramError(source_loc)
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<< "undefined behavior: store to subobject of uninitialized value "
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<< *values_[a.allocation_.index_];
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}
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states_[a.allocation_.index_] = ValueState::Alive;
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}
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CARBON_ASSIGN_OR_RETURN(values_[a.allocation_.index_],
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values_[a.allocation_.index_]->SetField(
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arena_, a.element_path_, v, source_loc));
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return Success();
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}
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auto Heap::CheckAlive(AllocationId allocation, SourceLocation source_loc) const
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-> ErrorOr<Success> {
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if (states_[allocation.index_] == ValueState::Dead ||
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states_[allocation.index_] == ValueState::Discarded) {
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return ProgramError(source_loc)
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<< "undefined behavior: access to dead or discarded value "
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<< *values_[allocation.index_];
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}
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return Success();
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}
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auto Heap::CheckInit(AllocationId allocation, SourceLocation source_loc) const
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-> ErrorOr<Success> {
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if (states_[allocation.index_] == ValueState::Uninitialized) {
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return ProgramError(source_loc)
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<< "undefined behavior: access to uninitialized value "
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<< *values_[allocation.index_];
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}
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return Success();
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}
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void Heap::Deallocate(AllocationId allocation) {
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if (states_[allocation.index_] != ValueState::Dead) {
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states_[allocation.index_] = ValueState::Dead;
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} else {
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CARBON_FATAL() << "deallocating an already dead value: "
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<< *values_[allocation.index_];
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}
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}
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void Heap::Deallocate(const Address& a) { Deallocate(a.allocation_); }
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auto Heap::is_initialized(AllocationId allocation) const -> bool {
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return states_[allocation.index_] != ValueState::Uninitialized;
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}
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auto Heap::is_discarded(AllocationId allocation) const -> bool {
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return states_[allocation.index_] == ValueState::Discarded;
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}
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void Heap::Discard(AllocationId allocation) {
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CARBON_CHECK(states_[allocation.index_] == ValueState::Uninitialized);
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states_[allocation.index_] = ValueState::Discarded;
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}
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void Heap::Print(llvm::raw_ostream& out) const {
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llvm::ListSeparator sep;
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for (size_t i = 0; i < values_.size(); ++i) {
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out << sep;
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out << i << ": ";
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if (states_[i] == ValueState::Uninitialized) {
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out << "!";
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} else if (states_[i] == ValueState::Dead) {
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out << "!!";
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}
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out << *values_[i];
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}
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}
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} // namespace Carbon
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