bjoernager/rust
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Remove print_vtable_sizes

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This commit is contained in:
Michael Goulet 2025-01-10 20:38:37 +00:00
parent 08d7e9dfe5
commit 37a430e6ea
5 changed files with 1 additions and 225 deletions
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91
compiler/rustc_interface/src/passes.rs
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@ -26,7 +26,6 @@ use rustc_parse::{
};
use rustc_passes::{abi_test, input_stats, layout_test};
use rustc_resolve::Resolver;
use rustc_session::code_stats::VTableSizeInfo;
use rustc_session::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
use rustc_session::cstore::Untracked;
use rustc_session::output::{collect_crate_types, filename_for_input, find_crate_name};
@ -989,90 +988,6 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) {
// we will fail to emit overlap diagnostics. Thus we invoke it here unconditionally.
let _ = tcx.all_diagnostic_items(());
});
if sess.opts.unstable_opts.print_vtable_sizes {
let traits = tcx.traits(LOCAL_CRATE);
for &tr in traits {
if !tcx.is_dyn_compatible(tr) {
continue;
}
let name = ty::print::with_no_trimmed_paths!(tcx.def_path_str(tr));
let mut first_dsa = true;
// Number of vtable entries, if we didn't have upcasting
let mut entries_ignoring_upcasting = 0;
// Number of vtable entries needed solely for upcasting
let mut entries_for_upcasting = 0;
let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, tr));
// A slightly edited version of the code in
// `rustc_trait_selection::traits::vtable::vtable_entries`, that works without self
// type and just counts number of entries.
//
// Note that this is technically wrong, for traits which have associated types in
// supertraits:
//
// trait A: AsRef<Self::T> + AsRef<()> { type T; }
//
// Without self type we can't normalize `Self::T`, so we can't know if `AsRef<Self::T>`
// and `AsRef<()>` are the same trait, thus we assume that those are different, and
// potentially over-estimate how many vtable entries there are.
//
// Similarly this is wrong for traits that have methods with possibly-impossible bounds.
// For example:
//
// trait B<T> { fn f(&self) where T: Copy; }
//
// Here `dyn B<u8>` will have 4 entries, while `dyn B<String>` will only have 3.
// However, since we don't know `T`, we can't know if `T: Copy` holds or not,
// thus we lean on the bigger side and say it has 4 entries.
traits::vtable::prepare_vtable_segments(tcx, trait_ref, |segment| {
match segment {
traits::vtable::VtblSegment::MetadataDSA => {
// If this is the first dsa, it would be included either way,
// otherwise it's needed for upcasting
if std::mem::take(&mut first_dsa) {
entries_ignoring_upcasting += 3;
} else {
entries_for_upcasting += 3;
}
}
traits::vtable::VtblSegment::TraitOwnEntries { trait_ref, emit_vptr } => {
// Lookup the shape of vtable for the trait.
let own_existential_entries =
tcx.own_existential_vtable_entries(trait_ref.def_id());
// The original code here ignores the method if its predicates are
// impossible. We can't really do that as, for example, all not trivial
// bounds on generic parameters are impossible (since we don't know the
// parameters...), see the comment above.
entries_ignoring_upcasting += own_existential_entries.len();
if emit_vptr {
entries_for_upcasting += 1;
}
}
}
std::ops::ControlFlow::Continue::<std::convert::Infallible>(())
});
sess.code_stats.record_vtable_size(tr, &name, VTableSizeInfo {
trait_name: name.clone(),
entries: entries_ignoring_upcasting + entries_for_upcasting,
entries_ignoring_upcasting,
entries_for_upcasting,
upcasting_cost_percent: entries_for_upcasting as f64
/ entries_ignoring_upcasting as f64
* 100.,
})
}
}
}
/// Check for the `#[rustc_error]` annotation, which forces an error in codegen. This is used
@ -1153,12 +1068,6 @@ pub(crate) fn start_codegen<'tcx>(
tcx.sess.code_stats.print_type_sizes();
}
if tcx.sess.opts.unstable_opts.print_vtable_sizes {
let crate_name = tcx.crate_name(LOCAL_CRATE);
tcx.sess.code_stats.print_vtable_sizes(crate_name);
}
codegen
}