blob: 3c756a86fc5a5e212eb99906c4c128a6786da2cb (
plain)
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
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
// run-pass
// Test that we don't duplicate storage for a variable that is moved to another
// binding. This used to happen in the presence of unwind and drop edges (see
// `complex` below.)
//
// The exact sizes here can change (we'd like to know when they do). What we
// don't want to see is the `complex` generator size being upwards of 2048 bytes
// (which would indicate it is reserving space for two copies of Foo.)
//
// See issue #59123 for a full explanation.
// edition:2018
// ignore-wasm32 issue #62807
// ignore-asmjs issue #62807
#![feature(generators, generator_trait)]
use std::ops::Generator;
const FOO_SIZE: usize = 1024;
struct Foo(#[allow(unused_tuple_struct_fields)] [u8; FOO_SIZE]);
impl Drop for Foo {
fn drop(&mut self) {}
}
fn move_before_yield() -> impl Generator<Yield = (), Return = ()> {
static || {
let first = Foo([0; FOO_SIZE]);
let _second = first;
yield;
// _second dropped here
}
}
fn noop() {}
fn move_before_yield_with_noop() -> impl Generator<Yield = (), Return = ()> {
static || {
let first = Foo([0; FOO_SIZE]);
noop();
let _second = first;
yield;
// _second dropped here
}
}
// Today we don't have NRVO (we allocate space for both `first` and `second`,)
// but we can overlap `first` with `_third`.
fn overlap_move_points() -> impl Generator<Yield = (), Return = ()> {
static || {
let first = Foo([0; FOO_SIZE]);
yield;
let second = first;
yield;
let _third = second;
yield;
}
}
fn overlap_x_and_y() -> impl Generator<Yield = (), Return = ()> {
static || {
let x = Foo([0; FOO_SIZE]);
yield;
drop(x);
let y = Foo([0; FOO_SIZE]);
yield;
drop(y);
}
}
fn main() {
assert_eq!(1025, std::mem::size_of_val(&move_before_yield()));
assert_eq!(1026, std::mem::size_of_val(&move_before_yield_with_noop()));
assert_eq!(2051, std::mem::size_of_val(&overlap_move_points()));
assert_eq!(1026, std::mem::size_of_val(&overlap_x_and_y()));
}
|
