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c4d9ada7
编写于
10月 08, 2017
作者:
E
Eduard-Mihai Burtescu
浏览文件
操作
浏览文件
下载
电子邮件补丁
差异文件
rustc: place ZSTs first during struct field reordering.
上级
cdeb4b0d
变更
1
隐藏空白更改
内联
并排
Showing
1 changed file
with
19 addition
and
22 deletion
+19
-22
src/librustc/ty/layout.rs
src/librustc/ty/layout.rs
+19
-22
未找到文件。
src/librustc/ty/layout.rs
浏览文件 @
c4d9ada7
...
...
@@ -964,40 +964,37 @@ enum StructKind {
let
mut
align
=
base_align
;
let
mut
primitive_align
=
base_align
;
let
mut
sized
=
true
;
let
mut
offsets
=
vec!
[
Size
::
from_bytes
(
0
);
fields
.len
()];
let
mut
inverse_memory_index
:
Vec
<
u32
>
=
(
0
..
fields
.len
()
as
u32
)
.collect
();
// Anything with repr(C) or repr(packed) doesn't optimize.
// Neither do 1-member and 2-member structs.
// In addition, code in trans assume that 2-element structs can become pairs.
// It's easier to just short-circuit here.
let
(
mut
optimize
,
sort_ascending
)
=
match
kind
{
let
optimize
=
match
kind
{
StructKind
::
AlwaysSized
|
StructKind
::
MaybeUnsized
=>
(
fields
.len
()
>
2
,
false
),
StructKind
::
EnumVariant
(
discr
)
=>
{
(
discr
.size
()
.bytes
()
==
1
,
true
)
StructKind
::
MaybeUnsized
|
StructKind
::
EnumVariant
(
I8
)
=>
{
(
repr
.flags
&
ReprFlags
::
IS_UNOPTIMISABLE
)
.is_empty
(
)
}
StructKind
::
EnumVariant
(
_
)
=>
false
};
optimize
&=
(
repr
.flags
&
ReprFlags
::
IS_UNOPTIMISABLE
)
.is_empty
();
let
mut
offsets
=
vec!
[
Size
::
from_bytes
(
0
);
fields
.len
()];
let
mut
inverse_memory_index
:
Vec
<
u32
>
=
(
0
..
fields
.len
()
as
u32
)
.collect
();
if
optimize
{
let
end
=
if
let
StructKind
::
MaybeUnsized
=
kind
{
fields
.len
()
-
1
}
else
{
fields
.len
()
};
if
end
>
0
{
let
optimizing
=
&
mut
inverse_memory_index
[
..
end
];
if
sort_ascending
{
let
optimizing
=
&
mut
inverse_memory_index
[
..
end
];
match
kind
{
StructKind
::
AlwaysSized
|
StructKind
::
MaybeUnsized
=>
{
optimizing
.sort_by_key
(|
&
x
|
{
// Place ZSTs first to avoid "interesting offsets",
// especially with only one or two non-ZST fields.
let
f
=
&
fields
[
x
as
usize
];
(
!
f
.is_zst
(),
cmp
::
Reverse
(
f
.align
.abi
()))
})
}
StructKind
::
EnumVariant
(
_
)
=>
{
optimizing
.sort_by_key
(|
&
x
|
fields
[
x
as
usize
]
.align
.abi
());
}
else
{
optimizing
.sort_by
(|
&
a
,
&
b
|
{
let
a
=
fields
[
a
as
usize
]
.align
.abi
();
let
b
=
fields
[
b
as
usize
]
.align
.abi
();
b
.cmp
(
&
a
)
});
}
}
}
...
...
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