mirror of
https://github.com/apple/swift.git
synced 2025-12-14 20:36:38 +01:00
d73a081fe7
Rig TransitiveAddressWalker to keep track of enough information for passes to correctly check for pointer escapes and dependence uses. Requires for precise bail-outs and asserts.
511 lines
17 KiB
C++
511 lines
17 KiB
C++
//===--- OwnershipUseVisitor.h -------------------------------*- C++ -*----===//
|
|
//
|
|
// This source file is part of the Swift.org open source project
|
|
//
|
|
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
|
|
// Licensed under Apache License v2.0 with Runtime Library Exception
|
|
//
|
|
// See https://swift.org/LICENSE.txt for license information
|
|
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
///
|
|
/// A visitor that classifies the uses of an OSSA value. The main entry points
|
|
/// are:
|
|
///
|
|
/// bool OwnershipUseVisitor::visitLifetimeEndingUses(SILValue ssaDef)
|
|
///
|
|
/// bool OwnershipUseVisitor::visitInteriorUses(SILValue ssaDef)
|
|
///
|
|
/// Extensions of the visitor determine how to handle pointer escapes,
|
|
/// reborrows, inner borrows, and scoped addresses.
|
|
|
|
#ifndef SWIFT_SIL_OWNERSHIPUSEVISITOR_H
|
|
#define SWIFT_SIL_OWNERSHIPUSEVISITOR_H
|
|
|
|
#include "swift/SIL/NodeBits.h"
|
|
#include "swift/SIL/OwnershipUtils.h"
|
|
#include "swift/SIL/ScopedAddressUtils.h"
|
|
#include "swift/SIL/SILArgument.h"
|
|
#include "swift/SIL/SILBasicBlock.h"
|
|
#include "swift/SIL/SILInstruction.h"
|
|
#include "swift/SIL/SILValue.h"
|
|
|
|
namespace swift {
|
|
|
|
enum class OwnershipUseKind { LifetimeEnding, NonLifetimeEnding };
|
|
|
|
/// Impl provides:
|
|
///
|
|
/// - NodeSet visited (if interior uses are visited)
|
|
///
|
|
/// - 'bool handleUsePoint(Operand *use, UseLifetimeConstraint)'
|
|
///
|
|
/// Where 'use->get()' is either the original SSA def, or the SILValue that
|
|
/// introduces an inner scope for which 'use' ends the scope.
|
|
///
|
|
/// Impl overrides:
|
|
///
|
|
/// - 'bool handlePointerEscape(Operand *use)' (default false)
|
|
///
|
|
/// - bool handleOwnedPhi(Operand *phiOper) { return true; }
|
|
///
|
|
/// - 'bool handleOuterReborrow(Operand *phiOper)' (default true)
|
|
///
|
|
/// - 'bool handleGuaranteedForward(Operand *use)' (default true)
|
|
///
|
|
/// - 'bool handleInnerBorrow(BorrowingOperand)' (default true)
|
|
///
|
|
/// - 'bool handleScopedAddress(ScopedAddressValue)' (default true)
|
|
///
|
|
/// These may be overridden with a transformation that adds uses to the use's
|
|
/// instruction or phi, but it may not modify the use-list containing \p
|
|
/// use or \p phiOper or in any outer scopes.
|
|
template <typename Impl>
|
|
class OwnershipUseVisitorBase {
|
|
protected:
|
|
/// If this returns true, then handleUsePoint will be called as if the pointer
|
|
/// escape is an instantaneous use. The implementation may decide to track
|
|
/// AddressUseKind::PointerEscaping. Bail-out by default for safety.
|
|
bool handlePointerEscape(Operand *use) {
|
|
return false;
|
|
}
|
|
|
|
/// Handle a owned forwarding phi of the original SSA def. Later, the phi
|
|
/// will itself be visited as a use but its scope's uses will not be
|
|
/// transitively visited. The implementation may track owned phis to
|
|
/// continue processing extended liveness.
|
|
///
|
|
/// Return true to continue visiting other uses.
|
|
bool handleOwnedPhi(Operand *phiOper) { return true; }
|
|
|
|
/// Handle a transitive reborrow of the original SSA def. Later, the reborrow
|
|
/// will itself be visited as a use but its scope's uses will not be
|
|
/// transitively visited. The implementation may track outer reborrows to
|
|
/// continue processing extended liveness.
|
|
///
|
|
/// Return true to continue visiting other uses.
|
|
///
|
|
/// Note: this can lead to infinite recursion if the client does not maintain
|
|
/// a visited set.
|
|
bool handleOuterReborrow(Operand *phiOper) { return true; }
|
|
|
|
/// Handle a guaranteed forwarding instruction. After the returns, this will
|
|
/// itself be visited as a use, but its uses will not be transitively
|
|
/// visited. The implementation may transtitively follow uses or track
|
|
/// unenclosed guaranteed phis to insert missing reborrows.
|
|
///
|
|
/// Return true to continue visiting other uses.
|
|
bool handleGuaranteedForwardingPhi(Operand *phiOper) { return true; }
|
|
|
|
/// If this returns true, then handleUsePoint will be called on the scope
|
|
/// ending operands.
|
|
///
|
|
/// Handles begin_borrow, load_borrow, store_borrow, begin_apply
|
|
///
|
|
/// Allows the implementation to complete inner scopes before considering
|
|
/// their scope ending operations as uses of the outer scope.
|
|
bool handleInnerBorrow(BorrowingOperand borrowingOperand) {
|
|
return true;
|
|
}
|
|
|
|
/// If this returns true, then handleUsePoint will be called on the scope
|
|
/// ending operands.
|
|
///
|
|
/// Allows the implementation to complete inner scopes before considering
|
|
/// their scope ending operations as uses of the outer scope.
|
|
///
|
|
/// This may add uses to the inner scope, but it may not modify the use-list
|
|
/// containing \p scopedAddress or in any outer scopes.
|
|
bool handleScopedAddress(ScopedAddressValue scopedAddress) {
|
|
return true;
|
|
}
|
|
};
|
|
|
|
/// Visit uses relevant to liveness of a single OSSA value.
|
|
template <typename Impl>
|
|
class OwnershipUseVisitor : OwnershipUseVisitorBase<Impl> {
|
|
protected:
|
|
Impl &asImpl() { return static_cast<Impl &>(*this); }
|
|
|
|
bool handleUsePoint(Operand *use, UseLifetimeConstraint useConstraint) {
|
|
asImpl().handleUsePoint(use, useConstraint);
|
|
return true;
|
|
}
|
|
|
|
public:
|
|
/// Assumes that ssaDef's lifetime is complete (linear).
|
|
bool visitLifetimeEndingUses(SILValue ssaDef);
|
|
|
|
/// Does not assume that ssaDef's lifetime is complete.
|
|
///
|
|
/// If ssaDef is either an owned phi or reborrow, then find inner adjacent
|
|
/// phis and treat them just like inner borrow scopes.
|
|
bool visitInteriorUses(SILValue ssaDef);
|
|
|
|
protected:
|
|
bool visitConsumes(SILValue ssaDef);
|
|
|
|
bool visitExtends(SILValue ssaDef);
|
|
|
|
bool visitOuterBorrow(SILValue borrowBegin);
|
|
|
|
bool visitOuterBorrowScopeEnd(Operand *borrowEnd);
|
|
|
|
bool visitInnerBorrow(Operand *borrowingOperand);
|
|
|
|
bool visitInnerBorrowScopeEnd(Operand *borrowEnd);
|
|
|
|
bool visitOwnedUse(Operand *use);
|
|
|
|
bool visitGuaranteedUses(SILValue guaranteedValue) {
|
|
for (Operand *use : guaranteedValue->getUses()) {
|
|
if (!visitGuaranteedUse(use))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool visitGuaranteedUse(Operand *use);
|
|
|
|
bool visitInteriorPointerUses(Operand *use);
|
|
};
|
|
|
|
/// Recursively visit all lifetime-ending uses that contribute to the ownership
|
|
/// live range of \p ssaDef. This assumes that ssaDef has a complete
|
|
/// lifetime and ignores non-lifetime-ending uses.
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitLifetimeEndingUses(SILValue ssaDef) {
|
|
switch (ssaDef->getOwnershipKind()) {
|
|
case OwnershipKind::Owned:
|
|
return visitConsumes(ssaDef);
|
|
|
|
case OwnershipKind::Guaranteed:
|
|
return visitOuterBorrow(ssaDef);
|
|
|
|
case OwnershipKind::None:
|
|
if (ssaDef->isFromVarDecl()) {
|
|
return visitExtends(ssaDef);
|
|
}
|
|
LLVM_FALLTHROUGH;
|
|
case OwnershipKind::Any:
|
|
case OwnershipKind::Unowned:
|
|
llvm_unreachable("requires an owned or guaranteed orignalDef");
|
|
}
|
|
return true;
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitConsumes(SILValue ssaDef) {
|
|
for (Operand *use : ssaDef->getUses()) {
|
|
// extend_lifetime instructions are non-consuming but need to be visited
|
|
// because together with consuming uses they enclose all users of the value.
|
|
if (isa<ExtendLifetimeInst>(use->getUser())) {
|
|
if (!handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding))
|
|
return false;
|
|
continue;
|
|
}
|
|
if (use->isConsuming()) {
|
|
if (PhiOperand(use) && !asImpl().handleOwnedPhi(use))
|
|
return false;
|
|
|
|
if (!handleUsePoint(use, UseLifetimeConstraint::LifetimeEnding))
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitExtends(SILValue ssaDef) {
|
|
for (Operand *use : ssaDef->getUses()) {
|
|
if (isa<ExtendLifetimeInst>(use->getUser())) {
|
|
if (!handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding))
|
|
return false;
|
|
continue;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitOuterBorrow(SILValue borrowBegin) {
|
|
BorrowedValue borrow(borrowBegin);
|
|
assert(borrow && "guaranteed values have no lifetime ending uses");
|
|
return borrow.visitLocalScopeEndingUses([this](Operand *borrowEnd) {
|
|
return visitOuterBorrowScopeEnd(borrowEnd);
|
|
});
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitOuterBorrowScopeEnd(Operand *borrowEnd) {
|
|
switch (borrowEnd->getOperandOwnership()) {
|
|
case OperandOwnership::EndBorrow:
|
|
return handleUsePoint(borrowEnd, UseLifetimeConstraint::LifetimeEnding);
|
|
|
|
case OperandOwnership::Reborrow:
|
|
if (!asImpl().handleOuterReborrow(borrowEnd))
|
|
return false;
|
|
|
|
return handleUsePoint(borrowEnd, UseLifetimeConstraint::LifetimeEnding);
|
|
|
|
case OperandOwnership::InstantaneousUse:
|
|
assert(isa<ExtendLifetimeInst>(borrowEnd->getUser()));
|
|
return handleUsePoint(borrowEnd, UseLifetimeConstraint::NonLifetimeEnding);
|
|
default:
|
|
llvm_unreachable("expected borrow scope end");
|
|
}
|
|
}
|
|
|
|
/// Visit the lifetime-ending uses of borrow scope
|
|
/// (begin_borrow, load_borrow, or begin_apply).
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitInnerBorrow(Operand *borrowingOperand) {
|
|
auto bo = BorrowingOperand(borrowingOperand);
|
|
assert(bo && "unexpected Borrow operand ownership");
|
|
if (bo.getScopeIntroducingUserResult()) {
|
|
if (!asImpl().handleInnerBorrow(borrowingOperand))
|
|
return false;
|
|
|
|
return bo.visitScopeEndingUses(
|
|
[&](Operand *borrowEnd) {
|
|
return visitInnerBorrowScopeEnd(borrowEnd);
|
|
},
|
|
[&](Operand *unknownUse) {
|
|
return asImpl().handlePointerEscape(unknownUse);
|
|
});
|
|
}
|
|
if (auto dependentValue = bo.getDependentUserResult()) {
|
|
switch (dependentValue->getOwnershipKind()) {
|
|
case OwnershipKind::Guaranteed:
|
|
if (!handleUsePoint(borrowingOperand,
|
|
UseLifetimeConstraint::NonLifetimeEnding)) {
|
|
return false;
|
|
}
|
|
return visitGuaranteedUses(dependentValue);
|
|
case OwnershipKind::Any:
|
|
case OwnershipKind::None:
|
|
case OwnershipKind::Owned: // non-escapable
|
|
case OwnershipKind::Unowned:
|
|
break;
|
|
}
|
|
}
|
|
return asImpl().handlePointerEscape(borrowingOperand);
|
|
}
|
|
|
|
/// Note: borrowEnd->get() may be a borrow introducer for an inner scope, or a
|
|
/// borrow scopes that does not introduce a borrowed value (begin_apply).
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitInnerBorrowScopeEnd(Operand *borrowEnd) {
|
|
switch (borrowEnd->getOperandOwnership()) {
|
|
case OperandOwnership::EndBorrow:
|
|
case OperandOwnership::Reborrow:
|
|
return handleUsePoint(borrowEnd, UseLifetimeConstraint::NonLifetimeEnding);
|
|
|
|
case OperandOwnership::DestroyingConsume:
|
|
case OperandOwnership::ForwardingConsume: {
|
|
// partial_apply [on_stack] and mark_dependence [nonescaping] can introduce
|
|
// borrowing operand and can have destroy_value, return, or store consumes.
|
|
//
|
|
// TODO: When we have a C++ ForwardingUseDefWalker, walk the use-def
|
|
// chain to ensure we have a partial_apply [on_stack] or mark_dependence
|
|
// [nonescaping] def.
|
|
return handleUsePoint(borrowEnd, UseLifetimeConstraint::NonLifetimeEnding);
|
|
}
|
|
case OperandOwnership::InstantaneousUse: {
|
|
auto builtinUser = dyn_cast<BuiltinInst>(borrowEnd->getUser());
|
|
if (builtinUser && builtinUser->getBuiltinKind() ==
|
|
BuiltinValueKind::EndAsyncLetLifetime) {
|
|
return handleUsePoint(borrowEnd,
|
|
UseLifetimeConstraint::NonLifetimeEnding);
|
|
}
|
|
LLVM_FALLTHROUGH;
|
|
}
|
|
default:
|
|
llvm_unreachable("expected borrow scope end");
|
|
}
|
|
}
|
|
|
|
/// Recursively visit all uses that contribute to the ownership live range of \p
|
|
/// ssaDef. This does not assume that ssaDef has a complete lifetime
|
|
/// and visits non-lifetime-ending uses.
|
|
///
|
|
/// If ssaDef is a phi (owned or reborrowed), then find its inner adjacent phis
|
|
/// and treat them like inner borrows.
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitInteriorUses(SILValue ssaDef) {
|
|
switch (ssaDef->getOwnershipKind()) {
|
|
case OwnershipKind::Owned: {
|
|
for (Operand *use : ssaDef->getUses()) {
|
|
if (!visitOwnedUse(use))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
case OwnershipKind::Guaranteed: {
|
|
return visitGuaranteedUses(ssaDef);
|
|
}
|
|
|
|
case OwnershipKind::Any:
|
|
case OwnershipKind::None:
|
|
case OwnershipKind::Unowned:
|
|
llvm_unreachable("requires an owned or guaranteed orignalDef");
|
|
}
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitOwnedUse(Operand *use) {
|
|
switch (use->getOperandOwnership()) {
|
|
case OperandOwnership::NonUse:
|
|
return true;
|
|
|
|
case OperandOwnership::ForwardingConsume:
|
|
case OperandOwnership::DestroyingConsume:
|
|
if (auto phiOper = PhiOperand(use)) {
|
|
if (!asImpl().handleOwnedPhi(use))
|
|
return false;
|
|
}
|
|
return handleUsePoint(use, UseLifetimeConstraint::LifetimeEnding);
|
|
|
|
case OperandOwnership::AnyInteriorPointer:
|
|
return visitInteriorPointerUses(use);
|
|
|
|
case OperandOwnership::PointerEscape:
|
|
// TODO: Change ProjectBox ownership to InteriorPointer and allow them to
|
|
// take owned values.
|
|
if (isa<ProjectBoxInst>(use->getUser())) {
|
|
return visitInteriorPointerUses(use);
|
|
}
|
|
if (!asImpl().handlePointerEscape(use))
|
|
return false;
|
|
|
|
LLVM_FALLTHROUGH;
|
|
case OperandOwnership::InstantaneousUse:
|
|
case OperandOwnership::ForwardingUnowned:
|
|
case OperandOwnership::UnownedInstantaneousUse:
|
|
case OperandOwnership::BitwiseEscape:
|
|
return handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding);
|
|
|
|
case OperandOwnership::Borrow:
|
|
return visitInnerBorrow(use);
|
|
|
|
// TODO: InteriorPointer should be handled like AnyInteriorPointer.
|
|
case OperandOwnership::InteriorPointer:
|
|
case OperandOwnership::TrivialUse:
|
|
case OperandOwnership::EndBorrow:
|
|
case OperandOwnership::Reborrow:
|
|
case OperandOwnership::GuaranteedForwarding:
|
|
llvm_unreachable("ownership incompatible with an owned value");
|
|
}
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitGuaranteedUse(Operand *use) {
|
|
switch (use->getOperandOwnership()) {
|
|
case OperandOwnership::NonUse:
|
|
return true;
|
|
|
|
case OperandOwnership::PointerEscape:
|
|
// TODO: Change ProjectBox ownership to InteriorPointer and allow them to
|
|
// take owned values.
|
|
if (isa<ProjectBoxInst>(use->getUser())) {
|
|
return visitInteriorPointerUses(use);
|
|
}
|
|
if (!asImpl().handlePointerEscape(use))
|
|
return false;
|
|
|
|
LLVM_FALLTHROUGH;
|
|
case OperandOwnership::InstantaneousUse:
|
|
case OperandOwnership::ForwardingUnowned:
|
|
case OperandOwnership::UnownedInstantaneousUse:
|
|
case OperandOwnership::BitwiseEscape:
|
|
return handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding);
|
|
case OperandOwnership::EndBorrow:
|
|
return handleUsePoint(use, UseLifetimeConstraint::LifetimeEnding);
|
|
|
|
case OperandOwnership::Reborrow:
|
|
if (!asImpl().handleOuterReborrow(use))
|
|
return false;
|
|
|
|
return handleUsePoint(use, UseLifetimeConstraint::LifetimeEnding);
|
|
|
|
case OperandOwnership::GuaranteedForwarding:
|
|
if (!handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding))
|
|
return false;
|
|
|
|
if (PhiOperand(use)) {
|
|
return asImpl().handleGuaranteedForwardingPhi(use);
|
|
}
|
|
|
|
if (!asImpl().visited.insert(use->getUser()->asSILNode()))
|
|
return true;
|
|
|
|
return ForwardingOperand(use).visitForwardedValues([&](SILValue result) {
|
|
// Do not include transitive uses with 'none' ownership
|
|
if (result->getOwnershipKind() != OwnershipKind::None) {
|
|
return visitGuaranteedUses(result);
|
|
}
|
|
return true;
|
|
});
|
|
|
|
case OperandOwnership::Borrow:
|
|
return visitInnerBorrow(use);
|
|
|
|
case OperandOwnership::InteriorPointer:
|
|
case OperandOwnership::AnyInteriorPointer:
|
|
return visitInteriorPointerUses(use);
|
|
|
|
case OperandOwnership::TrivialUse:
|
|
case OperandOwnership::ForwardingConsume:
|
|
case OperandOwnership::DestroyingConsume:
|
|
llvm_unreachable("ownership incompatible with a guaranteed value");
|
|
}
|
|
}
|
|
|
|
template <typename Impl>
|
|
bool OwnershipUseVisitor<Impl>::visitInteriorPointerUses(Operand *use) {
|
|
assert(use->getOperandOwnership() == OperandOwnership::InteriorPointer
|
|
|| use->getOperandOwnership() == OperandOwnership::AnyInteriorPointer
|
|
|| isa<ProjectBoxInst>(use->getUser()));
|
|
|
|
if (auto scopedAddress = ScopedAddressValue::forUse(use)) {
|
|
// e.g. client may need to insert end_borrow if scopedAddress is a store_borrow.
|
|
if (!asImpl().handleScopedAddress(scopedAddress))
|
|
return false;
|
|
|
|
return scopedAddress.visitScopeEndingUses([this](Operand *end) {
|
|
return handleUsePoint(end, UseLifetimeConstraint::NonLifetimeEnding);
|
|
});
|
|
}
|
|
handleUsePoint(use, UseLifetimeConstraint::NonLifetimeEnding);
|
|
|
|
auto interiorPtrOp = InteriorPointerOperand(use);
|
|
if (interiorPtrOp.getProjectedAddress()->use_empty()) {
|
|
// findTransitiveUses reports PointerEscape for a dead interior address. But
|
|
// the use-point was already recorded above. So it's safe to simply return.
|
|
return true;
|
|
}
|
|
|
|
// TODO: findTransitiveUses should be a visitor so we're not recursively
|
|
// allocating use vectors and potentially merging the use points.
|
|
//
|
|
// TODO: handleInnerBorrow needs to be called for any transitive load_borrow
|
|
// uses to ensure their lifetimes are complete. For now, findTransitiveUses
|
|
// just assumes that all scopes are incomplete.
|
|
SmallVector<Operand *, 8> interiorUses;
|
|
auto useKind = InteriorPointerOperand(use).findTransitiveUses(&interiorUses);
|
|
if (useKind != AddressUseKind::NonEscaping) {
|
|
if (!asImpl().handlePointerEscape(use))
|
|
return false;
|
|
}
|
|
for (auto *interiorUse : interiorUses) {
|
|
if (!handleUsePoint(interiorUse, UseLifetimeConstraint::NonLifetimeEnding))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
} // namespace swift
|
|
|
|
#endif
|