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//===--- SimplifySwitchEnum.swift -----------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
import SIL
// Removes an `enum` - `switch_enum` pair:
// ```
// %1 = enum $E, #someCase, %payload
// switch_enum %1, case #someCase: bb1, ...
// bb1(%payloadArgument):
// ```
// ->
// ```
// br bb1(%payload)
// bb1(%payloadArgument):
// ```
//
// Other case blocks of the switch_enum become dead.
//
extension SwitchEnumInst : OnoneSimplifyable {
func simplify(_ context: SimplifyContext) {
guard let enumInst = enumOp as? EnumInst,
let caseBlock = getUniqueSuccessor(forCaseIndex: enumInst.caseIndex) else
{
return
}
let singleUse = context.preserveDebugInfo ? enumInst.uses.singleUse : enumInst.uses.ignoreDebugUses.singleUse
let canEraseEnumInst = singleUse?.instruction == self
if !canEraseEnumInst && parentFunction.hasOwnership && enumInst.ownership == .owned {
// We cannot add more uses to the `enum` instruction without inserting a copy.
return
}
let builder = Builder(before: self, context)
switch caseBlock.arguments.count {
case 0:
precondition(enumInst.payload == nil || !parentFunction.hasOwnership,
"missing payload argument in switch_enum case block")
builder.createBranch(to: caseBlock)
context.erase(instruction: self)
case 1:
builder.createBranch(to: caseBlock, arguments: [enumInst.payload!])
context.erase(instruction: self)
updateBorrowedFrom(for: [Phi(caseBlock.arguments[0])!], context)
default:
fatalError("case block of switch_enum cannot have more than 1 argument")
}
if canEraseEnumInst {
context.erase(instructionIncludingDebugUses: enumInst)
}
}
}
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