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//===--- GuaranteedPhiUpdater.swift ---------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2024 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
//
//===----------------------------------------------------------------------===//
import SIL
import OptimizerBridging
/// Updates the reborrow flags and the borrowed-from instructions for all guaranteed phis in `function`.
func updateGuaranteedPhis(in function: Function, _ context: some MutatingContext) {
updateReborrowFlags(in: function, context)
updateBorrowedFrom(in: function, context)
}
/// Updates the reborrow flags and the borrowed-from instructions for all `phis`.
func updateGuaranteedPhis(phis: some Sequence<Phi>, _ context: some MutatingContext) {
updateReborrowFlags(for: phis, context)
updateBorrowedFrom(for: phis, context)
}
/// Update all borrowed-from instructions in the `function`
func updateBorrowedFrom(in function: Function, _ context: some MutatingContext) {
if !function.hasOwnership {
return
}
var guaranteedPhis = Stack<Phi>(context)
defer { guaranteedPhis.deinitialize() }
for block in function.blocks {
for arg in block.arguments {
if let phi = Phi(arg), phi.value.ownership == .guaranteed {
guaranteedPhis.append(phi)
}
}
}
updateBorrowedFrom(for: guaranteedPhis, context)
}
/// Update borrowed-from instructions for a set of phi arguments.
func updateBorrowedFrom(for phis: some Sequence<Phi>, _ context: some MutatingContext) {
for phi in phis {
if !phi.value.parentFunction.hasOwnership {
return
}
if phi.value.ownership == .guaranteed {
createBorrowedFrom(for: phi, context)
}
}
var changed: Bool
repeat {
changed = false
for phi in phis {
if phi.value.ownership == .guaranteed {
changed = updateBorrowedFrom(for: phi, context) || changed
}
}
} while changed
}
/// Updates the reborrow flags for all guaranteed phis in `function`.
func updateReborrowFlags(in function: Function, _ context: some MutatingContext) {
if !function.hasOwnership {
return
}
var guaranteedPhis = Stack<Phi>(context)
defer { guaranteedPhis.deinitialize() }
for block in function.blocks.reversed() {
for arg in block.arguments {
if let phi = Phi(arg), phi.value.ownership == .guaranteed {
guaranteedPhis.append(phi)
}
}
}
updateReborrowFlags(for: guaranteedPhis, context)
}
/// Updates the reborrow flags for all `phis`.
///
/// Re-borrow flags are only set, but never cleared. If an optimization creates a dead-end block
/// by cutting off the control flow before an `end_borrow`, the re-borrow flags still have to remain
/// without the possibility to re-calculate them from the (now missing) `end_borrow`.
///
func updateReborrowFlags(for phis: some Sequence<Phi>, _ context: some MutatingContext) {
if let phi = phis.first(where: { phi in true }), !phi.value.parentFunction.hasOwnership {
return
}
var changed: Bool
repeat {
changed = false
for phi in phis where phi.value.ownership == .guaranteed {
if !phi.value.isReborrow && phi.hasBorrowEndingUse {
phi.value.set(reborrow: true, context)
changed = true
}
}
} while changed
}
private func updateBorrowedFrom(for phi: Phi, _ context: some MutatingContext) -> Bool {
var computedEVs = Stack<Value>(context)
defer { computedEVs.deinitialize() }
gatherEnclosingValuesFromPredecessors(for: phi, in: &computedEVs, context)
var changed = false
for use in phi.value.uses {
if let bfi = use.forwardingBorrowedFromUser {
changed = addEnclosingValues(computedEVs, to: bfi, context) || changed
}
}
return changed
}
private func createBorrowedFrom(for phi: Phi, _ context: some MutatingContext) {
if !phi.value.uses.contains(where: { $0.forwardingBorrowedFromUser != nil }) {
let builder = Builder(atBeginOf: phi.value.parentBlock, context)
let bfi = builder.createBorrowedFrom(borrowedValue: phi.value, enclosingValues: [])
phi.value.uses.ignore(user: bfi).replaceAll(with: bfi, context)
}
}
private func addEnclosingValues(
_ newEVs: some Sequence<Value>,
to borrowedFrom: BorrowedFromInst,
_ context: some MutatingContext) -> Bool
{
var existingEVs = ValueSet(insertContentsOf: borrowedFrom.enclosingValues, context)
defer { existingEVs.deinitialize() }
if newEVs.allSatisfy({ existingEVs.contains($0) }) {
return false
}
var evs = Array<Value>(borrowedFrom.enclosingValues)
evs.append(contentsOf: newEVs.lazy.filter { !existingEVs.contains($0) })
let builder = Builder(before: borrowedFrom, context)
let newBfi = builder.createBorrowedFrom(borrowedValue: borrowedFrom.borrowedValue, enclosingValues: evs)
borrowedFrom.uses.replaceAll(with: newBfi, context)
context.erase(instruction: borrowedFrom)
return true
}
func registerGuaranteedPhiUpdater() {
BridgedUtilities.registerGuaranteedPhiUpdater(
{ (bridgedCtxt: BridgedPassContext, bridgedFunction: BridgedFunction) in
let context = FunctionPassContext(_bridged: bridgedCtxt)
let function = bridgedFunction.function;
updateGuaranteedPhis(in: function, context)
},
{ (bridgedCtxt: BridgedPassContext, bridgedPhiArray: BridgedArrayRef) in
let context = FunctionPassContext(_bridged: bridgedCtxt)
var guaranteedPhis = Stack<Phi>(context)
defer { guaranteedPhis.deinitialize() }
bridgedPhiArray.withElements(ofType: BridgedValue.self) {
for bridgedVal in $0 {
let phi = Phi(bridgedVal.value)!
if phi.value.ownership == .guaranteed {
guaranteedPhis.append(phi)
}
}
}
updateGuaranteedPhis(phis: guaranteedPhis, context)
}
)
}
/// This pass is only used for testing.
/// In the regular pipeline it's not needed because optimization passes must make sure that borrowed-from
/// instructions are updated once the pass finishes.
let updateBorrowedFromPass = FunctionPass(name: "update-borrowed-from") {
(function: Function, context: FunctionPassContext) in
updateBorrowedFrom(in: function, context)
}
|
