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969 lines
38 KiB
Swift
969 lines
38 KiB
Swift
//===--- EscapeUtils.swift ------------------------------------------------===//
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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 - 2022 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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//
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// This file provides utilities for transitively visiting all uses of a value.
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// The most common use case is to check if a value "escapes" to some destination
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// (e.g. an instruction) or if it "escapes" the current function at all.
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//
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// The APIs on `Value` and/or `ProjectedValue` are
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// * `isEscaping(using:)`
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// * `isEscapingWhenWalkingDown(using:)`
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// * `visit(using:)`
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// * `visitByWalkingDown(using:)`
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//
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// where a `EscapeVisitor` can be passed to the `using` argument to configure
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// the visit.
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//
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// The term "escaping" means that the "bit pattern" of the value is visible
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// at the destination. For example, in stack promotion we check if a reference to
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// an allocated object can escape it's function, i.e. if the bit pattern of the
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// reference can be visible outside it's function.
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// But it's also possible to check the "escapeness" of trivial values, e.g. an
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// `Int`. An `Int` escapes if its bit pattern is visible at the destination.
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// Though, by default trivial values are ignored. This can be configured with
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// `EscapeVisitor.followTrivialTypes`.
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//
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// By default, there is no distinction between addresses and value-type values.
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// Even if the value in question has an address type, it's considered escaping
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// if the stored value is escaping.
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// This can be configured with `EscapeVisitor.followLoads`.
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//
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// The visit algorithm works by starting a walk at the value and alternately
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// walking in two directions:
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// * Starting at root definitions, like allocations: walks down from defs to uses
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// ("Where does the value go to?")
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// * Starting at stores, walks up from uses to defs
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// ("Were does the value come from?")
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//
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// The value "escapes" if the walk reaches a point where the further flow of the value
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// cannot be tracked anymore.
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// Example:
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// \code
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// %1 = alloc_ref $X // 1. initial value: walk down to the `store`
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// %2 = alloc_stack $X // 3. walk down to %3
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// store %1 to %2 // 2. walk up to `%2`
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// %3 = load %2 // 4. continue walking down to the `return`
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// return %3 // 5. The value is escaping!
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// \endcode
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//
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// The traversal stops at points where the current path doesn't match the original projection.
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// For example, let's assume this function is called on a projected value with path `s0.c1`.
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// \code
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// %value : $Struct<X> // current path == s0.c1, the initial value
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// %ref = struct_extract %value, #field0 // current path == c1
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// %addr = ref_element_addr %ref, #field2 // mismatch: `c1` != `c2` -> ignored
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// \endcode
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//
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//===----------------------------------------------------------------------===//
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import SIL
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extension ProjectedValue {
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/// Returns true if the projected value escapes.
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///
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/// The provided `visitor` can be used to override the handling a certain defs and uses during
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/// the walk. See `EscapeVisitor` for details.
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///
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func isEscaping(
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using visitor: some EscapeVisitor = DefaultVisitor(),
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initialWalkingDirection: EscapeUtilityTypes.WalkingDirection = .up,
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complexityBudget: Int = Int.max,
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_ context: some Context
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) -> Bool {
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var walker = EscapeWalker(visitor: visitor, complexityBudget: complexityBudget, context)
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let result: WalkResult
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switch initialWalkingDirection {
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case .up: result = walker.walkUp(addressOrValue: value, path: path.escapePath)
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case .down: result = walker.walkDown(addressOrValue: value, path: path.escapePath)
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}
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return result == .abortWalk
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}
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/// Returns the result of the visitor if the projected value does not escape.
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///
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/// This function is similar to `isEscaping() -> Bool`, but instead of returning a Bool,
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/// it returns the `result` of the `visitor`, if the projected value does not escape.
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/// Returns nil, if the projected value escapes.
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///
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func visit<V: EscapeVisitorWithResult>(
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using visitor: V,
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initialWalkingDirection: EscapeUtilityTypes.WalkingDirection = .up,
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complexityBudget: Int = Int.max,
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_ context: some Context
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) -> V.Result? {
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var walker = EscapeWalker(visitor: visitor, complexityBudget: complexityBudget, context)
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let result: WalkResult
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switch initialWalkingDirection {
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case .up: result = walker.walkUp(addressOrValue: value, path: path.escapePath)
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case .down: result = walker.walkDown(addressOrValue: value, path: path.escapePath)
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}
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if result == .abortWalk {
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walker.visitor.cleanupOnAbort()
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return nil
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}
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return walker.visitor.result
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}
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}
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extension Value {
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/// The un-projected version of `ProjectedValue.isEscaping()`.
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func isEscaping(
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using visitor: some EscapeVisitor = DefaultVisitor(),
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initialWalkingDirection: EscapeUtilityTypes.WalkingDirection = .up,
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_ context: some Context
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) -> Bool {
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return self.at(SmallProjectionPath()).isEscaping(using: visitor,
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initialWalkingDirection: initialWalkingDirection,
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context)
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}
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/// The un-projected version of `ProjectedValue.visit()`.
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func visit<V: EscapeVisitorWithResult>(
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using visitor: V,
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initialWalkingDirection: EscapeUtilityTypes.WalkingDirection = .up,
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_ context: some Context
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) -> V.Result? {
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return self.at(SmallProjectionPath()).visit(using: visitor,
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initialWalkingDirection: initialWalkingDirection,
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context)
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}
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}
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/// This protocol is used to customize `ProjectedValue.isEscaping` (and similar functions)
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/// by implementing `visitUse` and `visitDef` which are called for all uses and definitions
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/// encountered during a walk.
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protocol EscapeVisitor {
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typealias UseResult = EscapeUtilityTypes.UseVisitResult
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typealias DefResult = EscapeUtilityTypes.DefVisitResult
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typealias EscapePath = EscapeUtilityTypes.EscapePath
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/// Called during the DefUse walk for each use
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mutating func visitUse(operand: Operand, path: EscapePath) -> UseResult
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/// Called during the UseDef walk for each definition
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mutating func visitDef(def: Value, path: EscapePath) -> DefResult
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/// If true, the traversals follow values with trivial types.
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var followTrivialTypes: Bool { get }
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/// If true, the traversal follows loaded values.
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var followLoads: Bool { get }
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}
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extension EscapeVisitor {
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mutating func visitUse(operand: Operand, path: EscapePath) -> UseResult {
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return .continueWalk
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}
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mutating func visitDef(def: Value, path: EscapePath) -> DefResult {
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return .continueWalkUp
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}
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var followTrivialTypes: Bool { false }
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var followLoads: Bool { true }
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}
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/// A visitor which returns a `result`.
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protocol EscapeVisitorWithResult : EscapeVisitor {
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associatedtype Result
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var result: Result { get }
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mutating func cleanupOnAbort()
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}
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extension EscapeVisitorWithResult {
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mutating func cleanupOnAbort() {}
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}
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// FIXME: This ought to be marked private, but that triggers a compiler bug
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// in debug builds (rdar://117413192)
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struct DefaultVisitor : EscapeVisitor {}
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struct EscapeUtilityTypes {
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enum WalkingDirection {
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case up
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case down
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}
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/// The EscapePath is updated and maintained during the up-walk and down-walk.
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///
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/// It's passed to the EscapeVisitor's `visitUse` and `visitDef`.
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struct EscapePath: SmallProjectionWalkingPath {
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/// During the walk, a projection path indicates where the initial value is
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/// contained in an aggregate.
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/// Example for a walk-down:
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/// \code
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/// %1 = alloc_ref // 1. initial value, path = empty
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/// %2 = struct $S (%1) // 2. path = s0
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/// %3 = tuple (%other, %1) // 3. path = t1.s0
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/// %4 = tuple_extract %3, 1 // 4. path = s0
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/// %5 = struct_extract %4, #field // 5. path = empty
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/// \endcode
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///
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let projectionPath: SmallProjectionPath
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/// This flag indicates if stored values should be included in the walk.
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/// If the initial value is stored to some memory allocation, we usually don't
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/// care if other values are stored to that location as well. Example:
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/// \code
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/// %1 = alloc_ref $X // 1. initial value, walk down to the `store`
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/// %2 = alloc_stack $X // 3. walk down to the second `store`
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/// store %1 to %2 // 2. walk up to %2
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/// store %other to %2 // 4. ignore (followStores == false): %other doesn't impact the "escapeness" of %1
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/// \endcode
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///
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/// But once the up-walk sees a load, it has to follow stores from that point on.
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/// Example:
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/// \code
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/// bb0(%function_arg): // 7. escaping! %1 escapes through %function_arg
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/// %1 = alloc_ref $X // 1. initial value, walk down to the second `store`
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/// %addr = alloc_stack %X // 5. walk down to the first `store`
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/// store %function_arg to %addr // 6. walk up to %function_arg (followStores == true)
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/// %2 = load %addr // 4. walk up to %addr, followStores = true
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/// %3 = ref_element_addr %2, #f // 3. walk up to %2
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/// store %1 to %3 // 2. walk up to %3
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/// \endcode
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///
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let followStores: Bool
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/// Set to true if an address is stored.
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/// This unusual situation can happen if an address is converted to a raw pointer and that pointer
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/// is stored to a memory location.
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/// In this case the walkers need to follow load instructions even if the visitor and current projection
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/// path don't say so.
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let addressIsStored: Bool
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/// Not nil, if the exact type of the current value is know.
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///
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/// This is used for destructor analysis.
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/// Example:
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/// \code
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/// %1 = alloc_ref $Derived // 1. initial value, knownType = $Derived
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/// %2 = upcast %1 to $Base // 2. knownType = $Derived
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/// destroy_value %2 : $Base // 3. We know that the destructor of $Derived is called here
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/// \endcode
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let knownType: Type?
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func with(projectionPath: SmallProjectionPath) -> Self {
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return Self(projectionPath: projectionPath, followStores: self.followStores,
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addressIsStored: self.addressIsStored, knownType: self.knownType)
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}
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func with(followStores: Bool) -> Self {
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return Self(projectionPath: self.projectionPath, followStores: followStores,
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addressIsStored: self.addressIsStored, knownType: self.knownType)
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}
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func with(addressStored: Bool) -> Self {
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return Self(projectionPath: self.projectionPath, followStores: self.followStores, addressIsStored: addressStored,
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knownType: self.knownType)
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}
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func with(knownType: Type?) -> Self {
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return Self(projectionPath: self.projectionPath, followStores: self.followStores,
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addressIsStored: self.addressIsStored, knownType: knownType)
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}
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func merge(with other: EscapePath) -> EscapePath {
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let mergedPath = self.projectionPath.merge(with: other.projectionPath)
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let mergedFollowStores = self.followStores || other.followStores
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let mergedAddrStored = self.addressIsStored || other.addressIsStored
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let mergedKnownType: Type?
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if let ty = self.knownType {
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if let otherTy = other.knownType, ty != otherTy {
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mergedKnownType = nil
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} else {
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mergedKnownType = ty
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}
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} else {
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mergedKnownType = other.knownType
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}
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return EscapePath(projectionPath: mergedPath, followStores: mergedFollowStores,
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addressIsStored: mergedAddrStored, knownType: mergedKnownType)
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}
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}
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enum DefVisitResult {
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case ignore
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case continueWalkUp
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case walkDown
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case abort
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}
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enum UseVisitResult {
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case ignore
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case continueWalk
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case abort
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}
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}
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/// EscapeWalker is both a DefUse walker and UseDef walker. It implements both, the up-, and down-walk.
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fileprivate struct EscapeWalker<V: EscapeVisitor> : ValueDefUseWalker,
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AddressDefUseWalker,
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ValueUseDefWalker,
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AddressUseDefWalker {
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typealias Path = EscapeUtilityTypes.EscapePath
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init(visitor: V, complexityBudget: Int = Int.max, _ context: some Context) {
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self.calleeAnalysis = context.calleeAnalysis
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self.visitor = visitor
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self.complexityBudget = complexityBudget
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}
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//===--------------------------------------------------------------------===//
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// Walking down
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//===--------------------------------------------------------------------===//
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mutating func walkDown(addressOrValue: Value, path: Path) -> WalkResult {
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if addressOrValue.type.isAddress {
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return walkDownUses(ofAddress: addressOrValue, path: path)
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} else {
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return walkDownUses(ofValue: addressOrValue, path: path)
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}
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}
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mutating func cachedWalkDown(addressOrValue: Value, path: Path) -> WalkResult {
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if let path = walkDownCache.needWalk(for: addressOrValue, path: path) {
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return walkDown(addressOrValue: addressOrValue, path: path)
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} else {
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return .continueWalk
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}
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}
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mutating func walkDown(value: Operand, path: Path) -> WalkResult {
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if complexityBudgetExceeded(value.value) {
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return .abortWalk
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}
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if hasRelevantType(value.value, at: path.projectionPath) {
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switch visitor.visitUse(operand: value, path: path) {
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case .continueWalk:
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return walkDownDefault(value: value, path: path)
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case .ignore:
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return .continueWalk
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case .abort:
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return .abortWalk
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}
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}
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return .continueWalk
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}
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/// ``ValueDefUseWalker`` conformance: called when the value def-use walk can't continue,
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/// i.e. when the result of the use is not a value.
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mutating func leafUse(value operand: Operand, path: Path) -> WalkResult {
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let instruction = operand.instruction
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switch instruction {
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case let rta as RefTailAddrInst:
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if let path = pop(.tailElements, from: path, yielding: rta) {
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return walkDownUses(ofAddress: rta, path: path.with(knownType: nil))
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}
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case let rea as RefElementAddrInst:
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if let path = pop(.classField, index: rea.fieldIndex, from: path, yielding: rea) {
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return walkDownUses(ofAddress: rea, path: path.with(knownType: nil))
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}
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case let pb as ProjectBoxInst:
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if let path = pop(.classField, index: pb.fieldIndex, from: path, yielding: pb) {
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return walkDownUses(ofAddress: pb, path: path.with(knownType: nil))
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}
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case is StoreInst, is StoreWeakInst, is StoreUnownedInst:
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let store = instruction as! StoringInstruction
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assert(operand == store.sourceOperand)
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if !followLoads(at: path) {
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return walkUp(address: store.destination, path: path.with(addressStored: true))
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}
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return walkUp(address: store.destination, path: path)
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case is DestroyValueInst, is ReleaseValueInst, is StrongReleaseInst:
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if handleDestroy(of: operand.value, path: path) == .abortWalk {
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return .abortWalk
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}
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case is ReturnInst:
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return isEscaping
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case is ApplyInst, is TryApplyInst, is BeginApplyInst:
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return walkDownCallee(argOp: operand, apply: instruction as! FullApplySite, path: path)
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case let pai as PartialApplyInst:
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// Check whether the partially applied argument can escape in the body.
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if walkDownCallee(argOp: operand, apply: pai, path: path.with(knownType: nil)) == .abortWalk {
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return .abortWalk
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}
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// Additionally we need to follow the partial_apply value for two reasons:
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// 1. the closure (with the captured values) itself can escape
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// and the use "transitively" escapes
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// 2. something can escape in a destructor when the context is destroyed
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return walkDownUses(ofValue: pai, path: path.with(knownType: nil))
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case let pta as PointerToAddressInst:
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return walkDownUses(ofAddress: pta, path: path.with(knownType: nil))
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case let cv as ConvertFunctionInst:
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return walkDownUses(ofValue: cv, path: path.with(knownType: nil))
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case let bi as BuiltinInst:
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switch bi.id {
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case .DestroyArray:
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// If it's not the array base pointer operand -> bail. Though, that shouldn't happen
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// because the other operands (metatype, count) shouldn't be visited anyway.
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if operand.index != 1 { return isEscaping }
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// Class references, which are directly located in the array elements cannot escape,
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// because those are passed as `self` to their deinits - and `self` cannot escape in a deinit.
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if !path.projectionPath.mayHaveClassProjection {
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return .continueWalk
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}
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return isEscaping
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case .AtomicLoad:
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// Treat atomic loads as regular loads and just walk down their uses.
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if !followLoads(at: path) {
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return .continueWalk
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}
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// Even when analyzing atomics, a loaded trivial value can be ignored.
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if hasRelevantType(bi, at: path.projectionPath) {
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return .continueWalk
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}
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return walkDownUses(ofValue: bi, path: path.with(knownType: nil))
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case .AtomicStore, .AtomicRMW:
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// If we shouldn't follow the store, then we can keep walking.
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if !path.followStores {
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return .continueWalk
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}
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// Be conservative and just say the store is escaping.
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return isEscaping
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case .CmpXChg:
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// If we have to follow loads or stores of a cmpxchg, then just bail.
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if followLoads(at: path) || path.followStores {
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return isEscaping
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}
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return .continueWalk
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case .Fence:
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// Fences do not affect escape analysis.
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return .continueWalk
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default:
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return isEscaping
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}
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case is StrongRetainInst, is RetainValueInst, is DebugValueInst, is ValueMetatypeInst,
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is InitExistentialMetatypeInst, is OpenExistentialMetatypeInst,
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is ExistentialMetatypeInst, is DeallocRefInst, is FixLifetimeInst,
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is ClassifyBridgeObjectInst, is BridgeObjectToWordInst, is EndBorrowInst,
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is StrongRetainInst, is RetainValueInst,
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is ClassMethodInst, is SuperMethodInst, is ObjCMethodInst,
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is ObjCSuperMethodInst, is WitnessMethodInst, is DeallocStackRefInst:
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return .continueWalk
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case is DeallocStackInst:
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// dealloc_stack %f : $@noescape @callee_guaranteed () -> ()
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// type is a value
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assert(operand.value.definingInstruction is PartialApplyInst)
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return .continueWalk
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default:
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|
return isEscaping
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
mutating func walkDown(address: Operand, path: Path) -> WalkResult {
|
|
if complexityBudgetExceeded(address.value) {
|
|
return .abortWalk
|
|
}
|
|
if hasRelevantType(address.value, at: path.projectionPath) {
|
|
switch visitor.visitUse(operand: address, path: path) {
|
|
case .continueWalk:
|
|
return walkDownDefault(address: address, path: path)
|
|
case .ignore:
|
|
return .continueWalk
|
|
case .abort:
|
|
return .abortWalk
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
/// ``AddressDefUseWalker`` conformance: called when the address def-use walk can't continue,
|
|
/// i.e. when the result of the use is not an address.
|
|
mutating func leafUse(address operand: Operand, path: Path) -> WalkResult {
|
|
let instruction = operand.instruction
|
|
switch instruction {
|
|
case is StoreInst, is StoreWeakInst, is StoreUnownedInst:
|
|
let store = instruction as! StoringInstruction
|
|
assert(operand == store.destinationOperand)
|
|
if let si = store as? StoreInst, si.storeOwnership == .assign {
|
|
if handleDestroy(of: operand.value, path: path.with(knownType: nil)) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
}
|
|
if path.followStores {
|
|
return walkUp(value: store.source, path: path)
|
|
}
|
|
case let storeBorrow as StoreBorrowInst:
|
|
assert(operand == storeBorrow.destinationOperand)
|
|
return walkDownUses(ofAddress: storeBorrow, path: path)
|
|
case let copyAddr as CopyAddrInst:
|
|
if !followLoads(at: path) {
|
|
return .continueWalk
|
|
}
|
|
if operand == copyAddr.sourceOperand {
|
|
return walkUp(address: copyAddr.destination, path: path)
|
|
} else {
|
|
if !copyAddr.isInitializationOfDest {
|
|
if handleDestroy(of: operand.value, path: path.with(knownType: nil)) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
}
|
|
|
|
if path.followStores {
|
|
assert(operand == copyAddr.destinationOperand)
|
|
return walkUp(value: copyAddr.source, path: path)
|
|
}
|
|
}
|
|
case is DestroyAddrInst:
|
|
if handleDestroy(of: operand.value, path: path) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
case is ReturnInst:
|
|
return isEscaping
|
|
case is ApplyInst, is TryApplyInst, is BeginApplyInst:
|
|
return walkDownCallee(argOp: operand, apply: instruction as! FullApplySite, path: path)
|
|
case let pai as PartialApplyInst:
|
|
if walkDownCallee(argOp: operand, apply: pai, path: path.with(knownType: nil)) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
|
|
// We need to follow the partial_apply value for two reasons:
|
|
// 1. the closure (with the captured values) itself can escape
|
|
// 2. something can escape in a destructor when the context is destroyed
|
|
return walkDownUses(ofValue: pai, path: path.with(knownType: nil))
|
|
case is LoadInst, is LoadWeakInst, is LoadUnownedInst, is LoadBorrowInst:
|
|
if !followLoads(at: path) {
|
|
return .continueWalk
|
|
}
|
|
let svi = instruction as! SingleValueInstruction
|
|
|
|
// Even when analyzing addresses, a loaded trivial value can be ignored.
|
|
if svi.hasTrivialNonPointerType { return .continueWalk }
|
|
return walkDownUses(ofValue: svi, path: path.with(knownType: nil))
|
|
case let atp as AddressToPointerInst:
|
|
return walkDownUses(ofValue: atp, path: path.with(knownType: nil))
|
|
case is DeallocStackInst, is InjectEnumAddrInst, is FixLifetimeInst, is EndBorrowInst, is EndAccessInst,
|
|
is IsUniqueInst, is DebugValueInst:
|
|
return .continueWalk
|
|
case let uac as UncheckedAddrCastInst:
|
|
if uac.type != uac.fromAddress.type {
|
|
// It's dangerous to continue walking over an `unchecked_addr_cast` which casts between two different types.
|
|
// We can only do this if the result is known to be the end of the walk, i.e. the cast result is not used
|
|
// in a relevant way.
|
|
for uacUse in uac.uses {
|
|
// Following instructions turned out to appear in code coming from the stdlib.
|
|
switch uacUse.instruction {
|
|
case is IsUniqueInst:
|
|
break
|
|
case is LoadInst, is LoadBorrowInst, is ApplyInst, is TryApplyInst:
|
|
if followLoads(at: path) {
|
|
return .abortWalk
|
|
}
|
|
default:
|
|
return .abortWalk
|
|
}
|
|
}
|
|
}
|
|
return walkDownUses(ofAddress: uac, path: path)
|
|
default:
|
|
return isEscaping
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
/// Check whether the value escapes through the deinitializer
|
|
private func handleDestroy(of value: Value, path: Path) -> WalkResult {
|
|
|
|
// Even if this is a destroy_value of a struct/tuple/enum, the called destructor(s) only take a
|
|
// single class reference as parameter.
|
|
let p = path.projectionPath.popAllValueFields()
|
|
|
|
if p.isEmpty {
|
|
// The object to destroy (= the argument of the destructor) cannot escape itself.
|
|
return .continueWalk
|
|
}
|
|
if !visitor.followLoads && p.matches(pattern: SmallProjectionPath(.anyValueFields).push(.anyClassField)) {
|
|
// Any address of a class property of the object to destroy cannot escape the destructor.
|
|
// (Whereas a value stored in such a property could escape.)
|
|
return .continueWalk
|
|
}
|
|
|
|
if path.followStores {
|
|
return isEscaping
|
|
}
|
|
if let exactTy = path.knownType {
|
|
guard let destructor = calleeAnalysis.getDestructor(ofExactType: exactTy) else {
|
|
return isEscaping
|
|
}
|
|
if destructor.effects.escapeEffects.canEscape(argumentIndex: 0, path: pathForArgumentEscapeChecking(p)) {
|
|
return isEscaping
|
|
}
|
|
} else {
|
|
// We don't know the exact type, so get all possible called destructure from
|
|
// the callee analysis.
|
|
guard let destructors = calleeAnalysis.getDestructors(of: value.type) else {
|
|
return isEscaping
|
|
}
|
|
for destructor in destructors {
|
|
if destructor.effects.escapeEffects.canEscape(argumentIndex: 0, path: pathForArgumentEscapeChecking(p)) {
|
|
return isEscaping
|
|
}
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
/// Handle an apply (full or partial) during the walk-down.
|
|
private mutating
|
|
func walkDownCallee(argOp: Operand, apply: ApplySite, path: Path) -> WalkResult {
|
|
guard let calleeArgIdx = apply.calleeArgumentIndex(of: argOp) else {
|
|
// The callee or a type dependent operand of the apply does not let escape anything.
|
|
return .continueWalk
|
|
}
|
|
|
|
// Indirect arguments cannot escape the function, but loaded values from such can.
|
|
if !followLoads(at: path) {
|
|
guard let beginApply = apply as? BeginApplyInst else {
|
|
return .continueWalk
|
|
}
|
|
// Except for begin_apply: it can yield an address value.
|
|
if !indirectResultEscapes(of: beginApply, path: path) {
|
|
return .continueWalk
|
|
}
|
|
}
|
|
|
|
if argOp.value.type.isNoEscapeFunction {
|
|
// Per definition a `partial_apply [on_stack]` cannot escape the callee.
|
|
// Potential escapes of its captured values are already handled when visiting the `partial_apply`.
|
|
return .continueWalk
|
|
}
|
|
|
|
// Argument effects do not consider any potential stores to the argument (or it's content).
|
|
// Therefore, if we need to track stores, the argument effects do not correctly describe what we need.
|
|
// For example, argument 0 in the following function is marked as not-escaping, although there
|
|
// is a store to the argument:
|
|
//
|
|
// sil [escapes !%0.**] @callee(@inout X, @owned X) -> () {
|
|
// bb0(%0 : $*X, %1 : $X):
|
|
// store %1 to %0 : $*X
|
|
// }
|
|
if path.followStores {
|
|
return isEscaping
|
|
}
|
|
|
|
guard let callees = calleeAnalysis.getCallees(callee: apply.callee) else {
|
|
// The callees are not know, e.g. if the callee is a closure, class method, etc.
|
|
return isEscaping
|
|
}
|
|
|
|
for callee in callees {
|
|
let effects = callee.effects
|
|
if !effects.escapeEffects.canEscape(argumentIndex: calleeArgIdx,
|
|
path: pathForArgumentEscapeChecking(path.projectionPath)) {
|
|
continue
|
|
}
|
|
if walkDownArgument(calleeArgIdx: calleeArgIdx, argPath: path,
|
|
apply: apply, effects: effects) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
private mutating func indirectResultEscapes(of beginApply: BeginApplyInst, path: Path) -> Bool {
|
|
for result in beginApply.yieldedValues where result.type.isAddress {
|
|
if walkDownUses(ofAddress: result, path: path) == .abortWalk {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
/// Handle `.escaping` effects for an apply argument during the walk-down.
|
|
private mutating
|
|
func walkDownArgument(calleeArgIdx: Int, argPath: Path,
|
|
apply: ApplySite, effects: FunctionEffects) -> WalkResult {
|
|
var matched = false
|
|
for effect in effects.escapeEffects.arguments {
|
|
switch effect.kind {
|
|
case .escapingToArgument(let toArgIdx, let toPath):
|
|
// Note: exclusive argument -> argument effects cannot appear, so we don't need to handle them here.
|
|
if effect.matches(calleeArgIdx, argPath.projectionPath) {
|
|
guard let argOp = apply.operand(forCalleeArgumentIndex: toArgIdx) else {
|
|
return isEscaping
|
|
}
|
|
|
|
// Continue at the destination of an arg-to-arg escape.
|
|
let arg = argOp.value
|
|
|
|
let p = Path(projectionPath: toPath, followStores: false, addressIsStored: argPath.addressIsStored,
|
|
knownType: nil)
|
|
if walkUp(addressOrValue: arg, path: p) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
matched = true
|
|
}
|
|
case .escapingToReturn(let toPath, let exclusive):
|
|
if effect.matches(calleeArgIdx, argPath.projectionPath) {
|
|
guard let fas = apply as? FullApplySite, let result = fas.singleDirectResult else {
|
|
return isEscaping
|
|
}
|
|
|
|
let p = Path(projectionPath: toPath, followStores: false, addressIsStored: argPath.addressIsStored,
|
|
knownType: exclusive ? argPath.knownType : nil)
|
|
|
|
if walkDownUses(ofValue: result, path: p) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
matched = true
|
|
}
|
|
case .notEscaping:
|
|
break
|
|
}
|
|
}
|
|
if !matched { return isEscaping }
|
|
return .continueWalk
|
|
}
|
|
|
|
//===--------------------------------------------------------------------===//
|
|
// Walking up
|
|
//===--------------------------------------------------------------------===//
|
|
|
|
mutating func walkUp(addressOrValue: Value, path: Path) -> WalkResult {
|
|
if addressOrValue.type.isAddress {
|
|
return walkUp(address: addressOrValue, path: path)
|
|
} else {
|
|
return walkUp(value: addressOrValue, path: path)
|
|
}
|
|
}
|
|
|
|
mutating func walkUp(value: Value, path: Path) -> WalkResult {
|
|
if complexityBudgetExceeded(value) {
|
|
return .abortWalk
|
|
}
|
|
if hasRelevantType(value, at: path.projectionPath) {
|
|
switch visitor.visitDef(def: value, path: path) {
|
|
case .continueWalkUp:
|
|
return walkUpDefault(value: value, path: path)
|
|
case .walkDown:
|
|
return cachedWalkDown(addressOrValue: value, path: path.with(knownType: nil))
|
|
case .ignore:
|
|
return .continueWalk
|
|
case .abort:
|
|
return .abortWalk
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
/// ``ValueUseDefWalker`` conformance: called when the value use-def walk can't continue,
|
|
/// i.e. when the operand (if any) of the instruction of a definition is not a value.
|
|
mutating func rootDef(value def: Value, path: Path) -> WalkResult {
|
|
switch def {
|
|
case is AllocRefInst, is AllocRefDynamicInst:
|
|
return cachedWalkDown(addressOrValue: def, path: path.with(knownType: def.type))
|
|
case is AllocBoxInst:
|
|
return cachedWalkDown(addressOrValue: def, path: path.with(knownType: nil))
|
|
case let arg as Argument:
|
|
guard let termResult = TerminatorResult(arg) else { return isEscaping }
|
|
switch termResult.terminator {
|
|
case let ta as TryApplyInst:
|
|
if termResult.successor != ta.normalBlock { return isEscaping }
|
|
return walkUpApplyResult(apply: ta, path: path.with(knownType: nil))
|
|
default:
|
|
return isEscaping
|
|
}
|
|
case let ap as ApplyInst:
|
|
return walkUpApplyResult(apply: ap, path: path.with(knownType: nil))
|
|
case is LoadInst, is LoadWeakInst, is LoadUnownedInst, is LoadBorrowInst:
|
|
if !followLoads(at: path) {
|
|
// When walking up we shouldn't end up at a load where followLoads is false,
|
|
// because going from a (non-followLoads) address to a load always involves a class indirection.
|
|
// There is one exception: loading a raw pointer, e.g.
|
|
// %l = load %a : $Builtin.RawPointer
|
|
// %a = pointer_to_address %l // the up-walk starts at %a
|
|
return isEscaping
|
|
}
|
|
return walkUp(address: (def as! UnaryInstruction).operand.value,
|
|
path: path.with(followStores: true).with(knownType: nil))
|
|
case let atp as AddressToPointerInst:
|
|
return walkUp(address: atp.address, path: path.with(knownType: nil))
|
|
default:
|
|
return isEscaping
|
|
}
|
|
}
|
|
|
|
mutating func walkUp(address: Value, path: Path) -> WalkResult {
|
|
if complexityBudgetExceeded(address) {
|
|
return .abortWalk
|
|
}
|
|
if hasRelevantType(address, at: path.projectionPath) {
|
|
switch visitor.visitDef(def: address, path: path) {
|
|
case .continueWalkUp:
|
|
return walkUpDefault(address: address, path: path)
|
|
case .walkDown:
|
|
return cachedWalkDown(addressOrValue: address, path: path)
|
|
case .ignore:
|
|
return .continueWalk
|
|
case .abort:
|
|
return .abortWalk
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
/// ``AddressUseDefWalker`` conformance: called when the address use-def walk can't continue,
|
|
/// i.e. when the operand (if any) of the instruction of a definition is not an address.
|
|
mutating func rootDef(address def: Value, path: Path) -> WalkResult {
|
|
switch def {
|
|
case is AllocStackInst:
|
|
return cachedWalkDown(addressOrValue: def, path: path.with(knownType: nil))
|
|
case let arg as FunctionArgument:
|
|
if !followLoads(at: path) && arg.convention.isExclusiveIndirect && !path.followStores {
|
|
return cachedWalkDown(addressOrValue: def, path: path.with(knownType: nil))
|
|
} else {
|
|
return isEscaping
|
|
}
|
|
case is PointerToAddressInst:
|
|
return walkUp(value: (def as! SingleValueInstruction).operands[0].value, path: path.with(knownType: nil))
|
|
case let rta as RefTailAddrInst:
|
|
return walkUp(value: rta.instance, path: path.push(.tailElements, index: 0).with(knownType: nil))
|
|
case let rea as RefElementAddrInst:
|
|
return walkUp(value: rea.instance, path: path.push(.classField, index: rea.fieldIndex).with(knownType: nil))
|
|
case let pb as ProjectBoxInst:
|
|
return walkUp(value: pb.box, path: path.push(.classField, index: pb.fieldIndex).with(knownType: nil))
|
|
case let storeBorrow as StoreBorrowInst:
|
|
return walkUp(address: storeBorrow.destination, path: path)
|
|
default:
|
|
return isEscaping
|
|
}
|
|
}
|
|
|
|
/// Walks up from the return to the source argument if there is an "exclusive"
|
|
/// escaping effect on an argument.
|
|
private mutating
|
|
func walkUpApplyResult(apply: FullApplySite,
|
|
path: Path) -> WalkResult {
|
|
guard let callees = calleeAnalysis.getCallees(callee: apply.callee) else {
|
|
return .abortWalk
|
|
}
|
|
|
|
for callee in callees {
|
|
var matched = false
|
|
for effect in callee.effects.escapeEffects.arguments {
|
|
switch effect.kind {
|
|
case .escapingToReturn(let toPath, let exclusive):
|
|
if exclusive && path.projectionPath.matches(pattern: toPath) {
|
|
guard let argOp = apply.operand(forCalleeArgumentIndex: effect.argumentIndex) else {
|
|
return .abortWalk
|
|
}
|
|
let arg = argOp.value
|
|
|
|
let p = Path(projectionPath: effect.pathPattern, followStores: path.followStores,
|
|
addressIsStored: path.addressIsStored, knownType: nil)
|
|
if walkUp(addressOrValue: arg, path: p) == .abortWalk {
|
|
return .abortWalk
|
|
}
|
|
matched = true
|
|
}
|
|
case .notEscaping, .escapingToArgument:
|
|
break
|
|
}
|
|
}
|
|
if !matched {
|
|
return isEscaping
|
|
}
|
|
}
|
|
return .continueWalk
|
|
}
|
|
|
|
//===--------------------------------------------------------------------===//
|
|
// private state
|
|
//===--------------------------------------------------------------------===//
|
|
|
|
var visitor: V
|
|
|
|
// The caches are not only useful for performance, but are need to avoid infinite
|
|
// recursions of walkUp-walkDown cycles.
|
|
var walkDownCache = WalkerCache<Path>()
|
|
var walkUpCache = WalkerCache<Path>()
|
|
|
|
// Only this number of up/and down walks are done until the walk aborts.
|
|
// Used to avoid quadratic complexity in some scenarios.
|
|
var complexityBudget: Int
|
|
|
|
private let calleeAnalysis: CalleeAnalysis
|
|
|
|
//===--------------------------------------------------------------------===//
|
|
// private utility functions
|
|
//===--------------------------------------------------------------------===//
|
|
|
|
/// Tries to pop the given projection from path, if the projected `value` has a relevant type.
|
|
private func pop(_ kind: Path.FieldKind, index: Int? = nil, from path: Path, yielding value: Value) -> Path? {
|
|
if let newPath = path.popIfMatches(kind, index: index),
|
|
hasRelevantType(value, at: newPath.projectionPath) {
|
|
return newPath
|
|
}
|
|
return nil
|
|
}
|
|
|
|
private func hasRelevantType(_ value: Value, at path: SmallProjectionPath) -> Bool {
|
|
if visitor.followTrivialTypes &&
|
|
// When part of a class field only need to follow non-trivial types
|
|
!path.hasClassProjection {
|
|
return true
|
|
}
|
|
if !value.hasTrivialNonPointerType {
|
|
return true
|
|
}
|
|
return false
|
|
}
|
|
|
|
private func followLoads(at path: Path) -> Bool {
|
|
return visitor.followLoads ||
|
|
// When part of a class field we have to follow loads.
|
|
path.projectionPath.mayHaveClassProjection ||
|
|
path.addressIsStored
|
|
}
|
|
|
|
private func pathForArgumentEscapeChecking(_ path: SmallProjectionPath) -> SmallProjectionPath {
|
|
if visitor.followLoads {
|
|
return path
|
|
}
|
|
return path.popLastClassAndValuesFromTail()
|
|
}
|
|
|
|
private mutating func complexityBudgetExceeded(_ v: Value) -> Bool {
|
|
if complexityBudget <= 0 {
|
|
return true
|
|
}
|
|
complexityBudget = complexityBudget &- 1
|
|
return false
|
|
}
|
|
|
|
// Set a breakpoint here to debug when a value is escaping.
|
|
private var isEscaping: WalkResult { .abortWalk }
|
|
}
|
|
|
|
private extension SmallProjectionPath {
|
|
var escapePath: EscapeUtilityTypes.EscapePath {
|
|
EscapeUtilityTypes.EscapePath(projectionPath: self, followStores: false, addressIsStored: false, knownType: nil)
|
|
}
|
|
}
|