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8d41f21aea
On the compiler side, `Borrow` ought to use extra inhabitants from its value representation, or at least the null pointer for the pointer representation. On the runtime side, the choice of representation needs to take size into account.
110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
//===--- Borrow.cpp - Swift Language Borrow Logic -------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2026 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#include "swift/Runtime/Borrow.h"
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#include "swift/Runtime/Metadata.h"
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namespace swift {
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BorrowRepresentation swift_getBorrowRepresentation(const Metadata *referent) {
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if (referent->getValueWitnesses()->getSize() > 4 * sizeof(uintptr_t)) {
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return BorrowRepresentation::Pointer;
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}
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if (!referent->getValueWitnesses()->isBitwiseBorrowable() ||
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referent->getValueWitnesses()->isAddressableForDependencies()) {
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return BorrowRepresentation::Pointer;
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}
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return BorrowRepresentation::Inline;
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}
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size_t swift_getBorrowSize(const Metadata *referent) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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return referent->vw_size();
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case BorrowRepresentation::Pointer:
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return $sBpWV.getSize();
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}
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}
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size_t swift_getBorrowStride(const Metadata *referent) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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return referent->vw_stride();
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case BorrowRepresentation::Pointer:
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return $sBpWV.getStride();
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}
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}
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size_t swift_getBorrowExtraInhabitants(const Metadata *referent) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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return referent->vw_getNumExtraInhabitants();
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case BorrowRepresentation::Pointer:
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return $sBpWV.getNumExtraInhabitants();
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}
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}
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size_t swift_getBorrowAlignment(const Metadata *referent) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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return referent->vw_alignment();
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case BorrowRepresentation::Pointer:
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return $sBpWV.getAlignment();
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}
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}
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SWIFT_RUNTIME_EXPORT
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void swift_initBorrow(const Metadata *referent, OpaqueValue *destBorrow,
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OpaqueValue *srcReferent) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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memcpy(destBorrow, srcReferent, referent->vw_size());
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return;
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case BorrowRepresentation::Pointer:
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*reinterpret_cast<OpaqueValue **>(destBorrow) = srcReferent;
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return;
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}
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}
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SWIFT_RUNTIME_EXPORT
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const OpaqueValue *swift_dereferenceBorrow(const Metadata *referent,
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const OpaqueValue *borrow) {
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auto rep = swift_getBorrowRepresentation(referent);
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switch (rep) {
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case BorrowRepresentation::Inline:
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return borrow;
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case BorrowRepresentation::Pointer:
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return *reinterpret_cast<const OpaqueValue * const *>(borrow);
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}
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}
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} // end namespace swift
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