mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-10-05 18:21:16 +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
98 lines
3.1 KiB
C++
98 lines
3.1 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_EXPLORER_AST_ADDRESS_H_
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#define CARBON_EXPLORER_AST_ADDRESS_H_
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#include <cstdint>
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#include <string>
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#include <vector>
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#include "common/check.h"
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#include "common/ostream.h"
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#include "explorer/ast/element_path.h"
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#include "llvm/Support/Compiler.h"
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namespace Carbon {
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// An AllocationId identifies an _allocation_ produced by a Heap. An allocation
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// is analogous to the C++ notion of a complete object: the `Value` in an
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// allocation is not a sub-part of any other `Value`.
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class AllocationId {
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public:
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AllocationId(const AllocationId&) = default;
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auto operator=(const AllocationId&) -> AllocationId& = default;
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// Prints a human-readable representation of *this to `out`.
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//
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// Currently that representation consists of an integer index.
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void Print(llvm::raw_ostream& out) const {
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out << "Allocation(" << index_ << ")";
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}
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private:
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// The representation of AllocationId describes how to locate an object within
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// a Heap, so its implementation details are tied to the implementation
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// details of Heap.
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friend class Heap;
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explicit AllocationId(size_t index) : index_(index) {}
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size_t index_;
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};
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// An Address represents a memory address in the Carbon virtual machine.
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// Addresses are used to access values stored in a Heap. Unlike an
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// AllocationId, an Address can refer to a sub-Value of some larger Value.
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class Address {
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public:
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// Constructs an `Address` that refers to the value stored in `allocation`.
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explicit Address(AllocationId allocation) : allocation_(allocation) {}
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Address(const Address&) = default;
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Address(Address&&) = default;
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auto operator=(const Address&) -> Address& = default;
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auto operator=(Address&&) -> Address& = default;
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// Prints a human-readable representation of `a` to `out`.
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//
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// Currently, that representation consists of an AllocationId followed by an
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// optional ElementPath specifying a particular field within that allocation.
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void Print(llvm::raw_ostream& out) const {
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out << allocation_ << element_path_;
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}
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LLVM_DUMP_METHOD void Dump() const { Print(llvm::errs()); }
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// If *this represents the address of an object with a field named
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// `field_name`, this method returns the address of that field.
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auto ElementAddress(Nonnull<const Element*> element) const -> Address {
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Address result = *this;
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result.element_path_.Append(element);
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return result;
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}
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// Drop all trailing BaseElements from the element path, returning the
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// downcasted address.
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auto DowncastedAddress() const -> Address {
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Address address = *this;
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address.element_path_.RemoveTrailingBaseElements();
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return address;
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}
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private:
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// The representation of Address describes how to locate an object within
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// the Heap, so its implementation details are tied to the implementation
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// details of the Heap.
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friend class Heap;
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friend class RuntimeScope;
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AllocationId allocation_;
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ElementPath element_path_;
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};
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} // namespace Carbon
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#endif // CARBON_EXPLORER_AST_ADDRESS_H_
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