1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
|
//===--- SimplifyGlobalValue.swift - Simplify global_value instruction ----===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2021 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 all reference counting instructions of a `global_value` instruction
// if it does not escape.
//
// Note that `simplifyStrongRetainPass` and `simplifyStrongReleasePass` can
// even remove "unbalanced" retains/releases of a `global_value`, but this
// requires a minimum deployment target.
extension GlobalValueInst : Simplifyable, SILCombineSimplifyable {
func simplify(_ context: SimplifyContext) {
var users = Stack<Instruction>(context)
defer { users.deinitialize() }
if checkUsers(of: self, users: &users) {
for inst in users {
context.erase(instruction: inst)
}
}
}
}
/// Returns true if reference counting and debug_value users of a global_value
/// can be deleted.
private func checkUsers(of val: Value, users: inout Stack<Instruction>) -> Bool {
for use in val.uses {
let user = use.instruction
switch user {
case is RefCountingInst, is DebugValueInst, is FixLifetimeInst:
users.push(user)
case let upCast as UpcastInst:
if !checkUsers(of: upCast, users: &users) {
return false
}
case is RefElementAddrInst, is RefTailAddrInst:
// Projection instructions don't access the object header, so they don't
// prevent deleting reference counting instructions.
break
default:
return false
}
}
return true
}
|
