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Auto merge of #67332 - matthewjasper:drop-in-place-cgus, r=michaelwoerister

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Don't instantiate so many copies of drop_in_place

Split out from #66703.

r? @ghost
This commit is contained in:
bors 2020-02-27 04:51:34 +00:00
commit d28560e660
4 changed files with 54 additions and 40 deletions
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23
src/librustc/ty/instance.rs
View file

@ -53,7 +53,10 @@ pub enum InstanceDef<'tcx> {
call_once: DefId,
},
/// `drop_in_place::<T>; None` for empty drop glue.
/// `core::ptr::drop_in_place::<T>`.
/// The `DefId` is for `core::ptr::drop_in_place`.
/// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
/// glue.
DropGlue(DefId, Option<Ty<'tcx>>),
///`<T as Clone>::clone` shim.
@ -176,12 +179,26 @@ impl<'tcx> InstanceDef<'tcx> {
if self.requires_inline(tcx) {
return true;
}
if let ty::InstanceDef::DropGlue(..) = *self {
// Drop glue wants to be instantiated at every codegen
if let ty::InstanceDef::DropGlue(.., Some(ty)) = *self {
// Drop glue generally wants to be instantiated at every codegen
// unit, but without an #[inline] hint. We should make this
// available to normal end-users.
if tcx.sess.opts.incremental.is_none() {
return true;
}
// When compiling with incremental, we can generate a *lot* of
// codegen units. Including drop glue into all of them has a
// considerable compile time cost.
//
// We include enums without destructors to allow, say, optimizing
// drops of `Option::None` before LTO. We also respect the intent of
// `#[inline]` on `Drop::drop` implementations.
return ty.ty_adt_def().map_or(true, |adt_def| {
adt_def.destructor(tcx).map_or(adt_def.is_enum(), |dtor| {
tcx.codegen_fn_attrs(dtor.did).requests_inline()
})
});
}
tcx.codegen_fn_attrs(self.def_id()).requests_inline()
}

13
src/librustc_mir/monomorphize/partitioning.rs
View file

@ -680,13 +680,20 @@ fn characteristic_def_id_of_mono_item<'tcx>(
if tcx.trait_of_item(def_id).is_some() {
let self_ty = instance.substs.type_at(0);
// This is an implementation of a trait method.
// This is a default implementation of a trait method.
return characteristic_def_id_of_type(self_ty).or(Some(def_id));
}
if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
// This is a method within an inherent impl, find out what the
// self-type is:
if tcx.sess.opts.incremental.is_some()
&& tcx.trait_id_of_impl(impl_def_id) == tcx.lang_items().drop_trait()
{
// Put `Drop::drop` into the same cgu as `drop_in_place`
// since `drop_in_place` is the only thing that can
// call it.
return None;
}
// This is a method within an impl, find out what the self-type is:
let impl_self_ty = tcx.subst_and_normalize_erasing_regions(
instance.substs,
ty::ParamEnv::reveal_all(),

17
src/test/codegen-units/partitioning/extern-drop-glue.rs
View file

@ -2,23 +2,23 @@
// We specify -Z incremental here because we want to test the partitioning for
// incremental compilation
// We specify opt-level=0 because `drop_in_place` is `Internal` when optimizing
// compile-flags:-Zprint-mono-items=lazy -Zincremental=tmp/partitioning-tests/extern-drop-glue
// compile-flags:-Zinline-in-all-cgus
// compile-flags:-Zinline-in-all-cgus -Copt-level=0
#![allow(dead_code)]
#![crate_type="rlib"]
#![crate_type = "rlib"]
// aux-build:cgu_extern_drop_glue.rs
extern crate cgu_extern_drop_glue;
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<cgu_extern_drop_glue::Struct[0]> @@ extern_drop_glue[Internal] extern_drop_glue-mod1[Internal]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<cgu_extern_drop_glue::Struct[0]> @@ extern_drop_glue-fallback.cgu[External]
struct LocalStruct(cgu_extern_drop_glue::Struct);
//~ MONO_ITEM fn extern_drop_glue::user[0] @@ extern_drop_glue[External]
pub fn user()
{
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<extern_drop_glue::LocalStruct[0]> @@ extern_drop_glue[Internal]
pub fn user() {
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<extern_drop_glue::LocalStruct[0]> @@ extern_drop_glue-fallback.cgu[External]
let _ = LocalStruct(cgu_extern_drop_glue::Struct(0));
}
@ -28,9 +28,8 @@ pub mod mod1 {
struct LocalStruct(cgu_extern_drop_glue::Struct);
//~ MONO_ITEM fn extern_drop_glue::mod1[0]::user[0] @@ extern_drop_glue-mod1[External]
pub fn user()
{
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<extern_drop_glue::mod1[0]::LocalStruct[0]> @@ extern_drop_glue-mod1[Internal]
pub fn user() {
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<extern_drop_glue::mod1[0]::LocalStruct[0]> @@ extern_drop_glue-fallback.cgu[External]
let _ = LocalStruct(cgu_extern_drop_glue::Struct(0));
}
}

39
src/test/codegen-units/partitioning/local-drop-glue.rs
View file

@ -1,54 +1,45 @@
// ignore-tidy-linelength
// We specify -Z incremental here because we want to test the partitioning for
// incremental compilation
// We specify opt-level=0 because `drop_in_place` is `Internal` when optimizing
// compile-flags:-Zprint-mono-items=lazy -Zincremental=tmp/partitioning-tests/local-drop-glue
// compile-flags:-Zinline-in-all-cgus
// compile-flags:-Zinline-in-all-cgus -Copt-level=0
#![allow(dead_code)]
#![crate_type="rlib"]
#![crate_type = "rlib"]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::Struct[0]> @@ local_drop_glue[Internal] local_drop_glue-mod1[Internal]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::Struct[0]> @@ local_drop_glue-fallback.cgu[External]
struct Struct {
_a: u32
_a: u32,
}
impl Drop for Struct {
//~ MONO_ITEM fn local_drop_glue::{{impl}}[0]::drop[0] @@ local_drop_glue[External]
//~ MONO_ITEM fn local_drop_glue::{{impl}}[0]::drop[0] @@ local_drop_glue-fallback.cgu[External]
fn drop(&mut self) {}
}
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::Outer[0]> @@ local_drop_glue[Internal]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::Outer[0]> @@ local_drop_glue-fallback.cgu[External]
struct Outer {
_a: Struct
_a: Struct,
}
//~ MONO_ITEM fn local_drop_glue::user[0] @@ local_drop_glue[External]
pub fn user()
{
let _ = Outer {
_a: Struct {
_a: 0
}
};
pub fn user() {
let _ = Outer { _a: Struct { _a: 0 } };
}
pub mod mod1
{
pub mod mod1 {
use super::Struct;
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::mod1[0]::Struct2[0]> @@ local_drop_glue-mod1[Internal]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<local_drop_glue::mod1[0]::Struct2[0]> @@ local_drop_glue-fallback.cgu[External]
struct Struct2 {
_a: Struct,
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<(u32, local_drop_glue::Struct[0])> @@ local_drop_glue-mod1[Internal]
//~ MONO_ITEM fn core::ptr[0]::drop_in_place[0]<(u32, local_drop_glue::Struct[0])> @@ local_drop_glue-fallback.cgu[Internal]
_b: (u32, Struct),
}
//~ MONO_ITEM fn local_drop_glue::mod1[0]::user[0] @@ local_drop_glue-mod1[External]
pub fn user()
{
let _ = Struct2 {
_a: Struct { _a: 0 },
_b: (0, Struct { _a: 0 }),
};
pub fn user() {
let _ = Struct2 { _a: Struct { _a: 0 }, _b: (0, Struct { _a: 0 }) };
}
}