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add tracing for layout optimizations

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The 8472 2023-03-05 16:18:19 +01:00
parent 4907dac54c
commit 351e208f4c
1 changed files with 44 additions and 0 deletions
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44
compiler/rustc_abi/src/layout.rs
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@ -1,4 +1,5 @@
use super::*;
use std::fmt::Write;
use std::{borrow::Borrow, cmp, iter, ops::Bound};
#[cfg(feature = "randomize")]
@ -72,12 +73,30 @@ fn univariant(
.expect("alt layout should have a niche like the regular one");
let alt_head_space = niche.offset.bytes();
let alt_niche_len = niche.value.size(dl).bytes();
let alt_tail_space = alt_layout.size.bytes() - alt_head_space - alt_niche_len;
debug_assert_eq!(layout.size.bytes(), alt_layout.size.bytes());
let prefer_alt_layout =
alt_head_space > head_space && alt_head_space > tail_space;
debug!(
"sz: {}, default_niche_at: {}+{}, default_tail_space: {}, alt_niche_at/head_space: {}+{}, alt_tail: {}, num_fields: {}, better: {}\n\
layout: {}\n\
alt_layout: {}\n",
layout.size.bytes(),
head_space,
niche_length,
tail_space,
alt_head_space,
alt_niche_len,
alt_tail_space,
layout.fields.count(),
prefer_alt_layout,
format_field_niches(&layout, &fields, &dl),
format_field_niches(&alt_layout, &fields, &dl),
);
if prefer_alt_layout {
return Some(alt_layout);
}
@ -1015,3 +1034,28 @@ fn univariant(
size,
})
}
fn format_field_niches(
layout: &LayoutS,
fields: &IndexSlice<FieldIdx, Layout<'_>>,
dl: &TargetDataLayout,
) -> String {
let mut s = String::new();
for i in layout.fields.index_by_increasing_offset() {
let offset = layout.fields.offset(i);
let f = fields[i.into()];
write!(s, "[o{}a{}s{}", offset.bytes(), f.align().abi.bytes(), f.size().bytes()).unwrap();
if let Some(n) = f.largest_niche() {
write!(
s,
" n{}b{}s{}",
n.offset.bytes(),
n.available(dl).ilog2(),
n.value.size(dl).bytes()
)
.unwrap();
}
write!(s, "] ").unwrap();
}
s
}