bjoernager/rust
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-Zprint-type-sizes: print the types of awaitees and unnamed coroutine locals.

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This should assist comprehending the size of coroutines.
In particular, whenever a future is suspended while awaiting another
future, the latter is given the special name `__awaitee`, and now the
type of the awaited future will be printed, allowing identifying
caller/callee — er, I mean, poller/pollee — relationships.

It would be possible to include the type name in more cases, but I
thought that that might be overly verbose (`print-type-sizes` is already
a lot of text) and ordinary named fields or variables are easier for
readers to discover the types of.
This commit is contained in:
Kevin Reid 2024-03-22 16:45:32 -07:00
parent 85e449a323
commit 44d185b0d0
5 changed files with 34 additions and 16 deletions
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10
compiler/rustc_ty_utils/src/layout.rs
View file

@ -10,6 +10,7 @@ use rustc_middle::ty::layout::{
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, AdtDef, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
use rustc_span::sym;
use rustc_span::symbol::Symbol;
use rustc_target::abi::*;
@ -1007,6 +1008,7 @@ fn variant_info_for_adt<'tcx>(
offset: offset.bytes(),
size: field_layout.size.bytes(),
align: field_layout.align.abi.bytes(),
type_name: None,
}
})
.collect();
@ -1090,6 +1092,7 @@ fn variant_info_for_coroutine<'tcx>(
offset: offset.bytes(),
size: field_layout.size.bytes(),
align: field_layout.align.abi.bytes(),
type_name: None,
}
})
.collect();
@ -1104,19 +1107,24 @@ fn variant_info_for_coroutine<'tcx>(
.iter()
.enumerate()
.map(|(field_idx, local)| {
let field_name = coroutine.field_names[*local];
let field_layout = variant_layout.field(cx, field_idx);
let offset = variant_layout.fields.offset(field_idx);
// The struct is as large as the last field's end
variant_size = variant_size.max(offset + field_layout.size);
FieldInfo {
kind: FieldKind::CoroutineLocal,
name: coroutine.field_names[*local].unwrap_or(Symbol::intern(&format!(
name: field_name.unwrap_or(Symbol::intern(&format!(
".coroutine_field{}",
local.as_usize()
))),
offset: offset.bytes(),
size: field_layout.size.bytes(),
align: field_layout.align.abi.bytes(),
// Include the type name if there is no field name, or if the name is the
// __awaitee placeholder symbol which means a child future being `.await`ed.
type_name: (field_name.is_none() || field_name == Some(sym::__awaitee))
.then(|| Symbol::intern(&field_layout.ty.to_string())),
}
})
.chain(upvar_fields.iter().copied())