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67 lines
2.6 KiB
C++
67 lines
2.6 KiB
C++
//===--- OwnershipConversionElimination.cpp -------------------------------===//
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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) 2014 - 2020 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 "SemanticARC/SemanticARCOpts.h"
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#include "SemanticARCOptVisitor.h"
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#include "swift/SIL/LinearLifetimeChecker.h"
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using namespace swift;
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using namespace semanticarc;
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//===----------------------------------------------------------------------===//
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// Top Level Entrypoint
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//===----------------------------------------------------------------------===//
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bool SemanticARCOptVisitor::visitUncheckedOwnershipConversionInst(
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UncheckedOwnershipConversionInst *uoci) {
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// Return false if we are supposed to only be running guaranteed opts.
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if (ctx.onlyMandatoryOpts)
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return false;
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// Then check if we are running tests and shouldn't perform this optimization
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// since we are testing something else.
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if (!ctx.shouldPerform(ARCTransformKind::OwnershipConversionElimPeephole))
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return false;
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// Otherwise, shrink our state space so that we only consider conversions from
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// owned or guaranteed to unowned. These are always legal and it is sometimes
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// convenient to insert them to avoid forwarding issues when RAUWing
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// values. So we eliminate them here.
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if (uoci->getConversionOwnershipKind() != OwnershipKind::Unowned)
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return false;
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auto op = uoci->getOperand();
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auto opKind = op->getOwnershipKind();
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if (opKind != OwnershipKind::Owned && opKind != OwnershipKind::Guaranteed)
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return false;
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// Ok, we can perform our optimization. First go through all of the uses of
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// uoci and see if they can accept our operand without any changes and that
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// they do not consume values.
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SmallVector<Operand *, 8> newUses;
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for (auto *use : uoci->getUses()) {
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if (use->isLifetimeEnding() || !use->canAcceptKind(opKind))
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return false;
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newUses.push_back(use);
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}
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// Ok, now we need to perform our lifetime check.
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SmallVector<Operand *, 8> consumingUses(op->getConsumingUses());
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LinearLifetimeChecker checker(&ctx.getDeadEndBlocks());
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if (!checker.validateLifetime(op, consumingUses, newUses))
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return false;
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// Otherwise, we can perform our rauw.
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eraseAndRAUWSingleValueInstruction(uoci, op);
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return true;
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}
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