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More clone shim cleanups #48063

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More clone shim cleanups #48063

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8bdb10d
Use InstanceDef::Item for clone_from shims
Manishearth Feb 7, 2018
d45a70c
Split CloneShim into CloneCopyShim, CloneStructuralShim, CloneNominal…
Manishearth Feb 7, 2018
9898cff
Remove ty from CloneCopyShim so that it creates a single shim for all…
Manishearth Feb 7, 2018
2c33d2f
Pass down the self def id instead of the type
Manishearth Feb 7, 2018
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9 changes: 8 additions & 1 deletion src/librustc/ich/impls_ty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -758,7 +758,14 @@ impl<'gcx> HashStable<StableHashingContext<'gcx>> for ty::InstanceDef<'gcx> {
def_id.hash_stable(hcx, hasher);
t.hash_stable(hcx, hasher);
}
ty::InstanceDef::CloneShim(def_id, t) => {
ty::InstanceDef::CloneCopyShim(def_id) => {
def_id.hash_stable(hcx, hasher);
}
ty::InstanceDef::CloneNominalShim { clone, ty } => {
clone.hash_stable(hcx, hasher);
ty.hash_stable(hcx, hasher);
}
ty::InstanceDef::CloneStructuralShim(def_id, t) => {
def_id.hash_stable(hcx, hasher);
t.hash_stable(hcx, hasher);
}
Expand Down
56 changes: 50 additions & 6 deletions src/librustc/ty/instance.rs
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Expand Up @@ -13,6 +13,7 @@ use ty::{self, Ty, TypeFoldable, Substs, TyCtxt};
use ty::subst::Kind;
use traits;
use syntax::abi::Abi;
use syntax::codemap::DUMMY_SP;
use util::ppaux;

use std::fmt;
Expand All @@ -39,10 +40,25 @@ pub enum InstanceDef<'tcx> {
ClosureOnceShim { call_once: DefId },

/// drop_in_place::<T>; None for empty drop glue.
///
/// The DefId is the DefId of drop_in_place
DropGlue(DefId, Option<Ty<'tcx>>),

///`<T as Clone>::clone` shim.
CloneShim(DefId, Ty<'tcx>),
///`<T as Clone>::clone` shim for Copy types
///
/// The DefId is the DefId of the Clone::clone function
CloneCopyShim(DefId),
///`<T as Clone>::clone` shim for arrays and tuples
///
/// The DefId is the DefId of the Clone::clone function
CloneStructuralShim(DefId, Ty<'tcx>),
///`<T as Clone>::clone` shim for closures
CloneNominalShim {
/// The DefId of the Clone::clone trait method def
clone: DefId,
/// The DefId of the self type
ty: DefId
},
}

impl<'a, 'tcx> Instance<'tcx> {
Expand All @@ -65,7 +81,9 @@ impl<'tcx> InstanceDef<'tcx> {
InstanceDef::Intrinsic(def_id, ) |
InstanceDef::ClosureOnceShim { call_once: def_id } |
InstanceDef::DropGlue(def_id, _) |
InstanceDef::CloneShim(def_id, _) => def_id
InstanceDef::CloneCopyShim(def_id) |
InstanceDef::CloneStructuralShim(def_id, _) |
InstanceDef::CloneNominalShim{ clone: def_id, ..} => def_id
}
}

Expand Down Expand Up @@ -131,7 +149,11 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
InstanceDef::DropGlue(_, ty) => {
write!(f, " - shim({:?})", ty)
}
InstanceDef::CloneShim(_, ty) => {
InstanceDef::CloneCopyShim(def) |
InstanceDef::CloneNominalShim { ty: def, ..} => {
write!(f, " - shim({:?})", def)
}
InstanceDef::CloneStructuralShim(_, ty) => {
write!(f, " - shim({:?})", ty)
}
}
Expand Down Expand Up @@ -289,9 +311,31 @@ fn resolve_associated_item<'a, 'tcx>(
}
traits::VtableBuiltin(..) => {
if let Some(_) = tcx.lang_items().clone_trait() {
let mut substs = rcvr_substs;
let name = tcx.item_name(def_id);
let def = if name == "clone" {
let self_ty = trait_ref.self_ty();
match self_ty.sty {
_ if !self_ty.moves_by_default(tcx, param_env, DUMMY_SP) => {
ty::InstanceDef::CloneCopyShim(def_id)
}
ty::TyArray(..) => ty::InstanceDef::CloneStructuralShim(def_id, self_ty),
ty::TyTuple(..) => ty::InstanceDef::CloneStructuralShim(def_id, self_ty),
ty::TyClosure(ty_did, closure_substs) => {
substs = closure_substs.substs;
ty::InstanceDef::CloneNominalShim {
clone: def_id,
ty: ty_did
}
}
_ => unreachable!("Type {:?} does not have clone shims", self_ty)
}
} else {
ty::InstanceDef::Item(def_id)
};
Some(Instance {
def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
substs: rcvr_substs
def,
substs
})
} else {
None
Expand Down
4 changes: 3 additions & 1 deletion src/librustc/ty/mod.rs
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Expand Up @@ -2351,7 +2351,9 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
ty::InstanceDef::Virtual(..) |
ty::InstanceDef::ClosureOnceShim { .. } |
ty::InstanceDef::DropGlue(..) |
ty::InstanceDef::CloneShim(..) => {
ty::InstanceDef::CloneCopyShim(..) |
ty::InstanceDef::CloneStructuralShim(..) |
ty::InstanceDef::CloneNominalShim { .. } => {
self.mir_shims(instance)
}
}
Expand Down
4 changes: 3 additions & 1 deletion src/librustc_mir/interpret/terminator/mod.rs
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Expand Up @@ -295,7 +295,9 @@ impl<'a, 'tcx, M: Machine<'tcx>> EvalContext<'a, 'tcx, M> {
}
ty::InstanceDef::FnPtrShim(..) |
ty::InstanceDef::DropGlue(..) |
ty::InstanceDef::CloneShim(..) |
ty::InstanceDef::CloneCopyShim(..) |
ty::InstanceDef::CloneStructuralShim(..) |
ty::InstanceDef::CloneNominalShim { .. } |
ty::InstanceDef::Item(_) => {
// Push the stack frame, and potentially be entirely done if the call got hooked
if M::eval_fn_call(self, instance, destination, args, span, sig)? {
Expand Down
8 changes: 6 additions & 2 deletions src/librustc_mir/monomorphize/collector.rs
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Expand Up @@ -711,7 +711,9 @@ fn visit_instance_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
ty::InstanceDef::ClosureOnceShim { .. } |
ty::InstanceDef::Item(..) |
ty::InstanceDef::FnPtrShim(..) |
ty::InstanceDef::CloneShim(..) => {
ty::InstanceDef::CloneCopyShim(..) |
ty::InstanceDef::CloneStructuralShim(..) |
ty::InstanceDef::CloneNominalShim { .. } => {
output.push(create_fn_mono_item(instance));
}
}
Expand All @@ -729,7 +731,9 @@ fn should_monomorphize_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance:
ty::InstanceDef::FnPtrShim(..) |
ty::InstanceDef::DropGlue(..) |
ty::InstanceDef::Intrinsic(_) |
ty::InstanceDef::CloneShim(..) => return true
ty::InstanceDef::CloneCopyShim(..) |
ty::InstanceDef::CloneStructuralShim(..) |
ty::InstanceDef::CloneNominalShim { .. } => return true
};
match tcx.hir.get_if_local(def_id) {
Some(hir_map::NodeForeignItem(..)) => {
Expand Down
12 changes: 9 additions & 3 deletions src/librustc_mir/monomorphize/partitioning.rs
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Expand Up @@ -175,7 +175,9 @@ pub trait CodegenUnitExt<'tcx> {
InstanceDef::Virtual(..) |
InstanceDef::ClosureOnceShim { .. } |
InstanceDef::DropGlue(..) |
InstanceDef::CloneShim(..) => {
InstanceDef::CloneCopyShim(..) |
InstanceDef::CloneStructuralShim(..) |
InstanceDef::CloneNominalShim { .. } => {
None
}
}
Expand Down Expand Up @@ -376,7 +378,9 @@ fn place_root_translation_items<'a, 'tcx, I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
InstanceDef::Intrinsic(..) |
InstanceDef::ClosureOnceShim { .. } |
InstanceDef::DropGlue(..) |
InstanceDef::CloneShim(..) => {
InstanceDef::CloneCopyShim(..) |
InstanceDef::CloneStructuralShim(..) |
InstanceDef::CloneNominalShim { .. } => {
Visibility::Hidden
}
};
Expand Down Expand Up @@ -619,7 +623,9 @@ fn characteristic_def_id_of_trans_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
ty::InstanceDef::Intrinsic(..) |
ty::InstanceDef::DropGlue(..) |
ty::InstanceDef::Virtual(..) |
ty::InstanceDef::CloneShim(..) => return None
ty::InstanceDef::CloneCopyShim(..) |
ty::InstanceDef::CloneStructuralShim(..) |
ty::InstanceDef::CloneNominalShim { .. } => return None
};

// If this is a method, we want to put it into the same module as
Expand Down
25 changes: 13 additions & 12 deletions src/librustc_mir/shim.rs
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Expand Up @@ -99,16 +99,19 @@ fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
ty::InstanceDef::DropGlue(def_id, ty) => {
build_drop_shim(tcx, def_id, ty)
}
ty::InstanceDef::CloneShim(def_id, ty) => {
let name = tcx.item_name(def_id);
if name == "clone" {
build_clone_shim(tcx, def_id, ty)
} else if name == "clone_from" {
debug!("make_shim({:?}: using default trait implementation", instance);
return tcx.optimized_mir(def_id);
} else {
bug!("builtin clone shim {:?} not supported", instance)
}
ty::InstanceDef::CloneCopyShim(def_id) => {
let substs = Substs::identity_for_item(tcx, def_id);
let self_ty = substs.type_at(0);
let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
builder.copy_shim();
builder.into_mir()
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I..don't understand this. How can we have just one shim for all monomorphizations? Don't their sizes depend on the specific types in use?

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And what does this DefId refer to anyhow?

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Shims are not per-monomorphization, they're pretty generic (look at some of the other ones). CloneShim (and now the CloneStructuralShim) was incorrectly too monomorphic (but the array/tuple cases are harder to fix).

What's happening now is that there's only one MIR body forreturn *self; and one per closure definition, which you monomorphize just like you'd monomorphize a generic closure definition.

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"One shim for all monomorphizations" is the reason behind this PR. As for how it works, ask @eddyb

}
ty::InstanceDef::CloneNominalShim { clone, ty } => {
let ty = tcx.type_of(ty);
build_clone_shim(tcx, clone, ty)
}
ty::InstanceDef::CloneStructuralShim(def_id, ty) => {
build_clone_shim(tcx, def_id, ty)
}
ty::InstanceDef::Intrinsic(_) => {
bug!("creating shims from intrinsics ({:?}) is unsupported", instance)
Expand Down Expand Up @@ -295,13 +298,11 @@ fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
debug!("build_clone_shim(def_id={:?})", def_id);

let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
let is_copy = !self_ty.moves_by_default(tcx, tcx.param_env(def_id), builder.span);

let dest = Place::Local(RETURN_PLACE);
let src = Place::Local(Local::new(1+0)).deref();

match self_ty.sty {
_ if is_copy => builder.copy_shim(),
ty::TyArray(ty, len) => {
let len = len.val.to_const_int().unwrap().to_u64().unwrap();
builder.array_shim(dest, src, ty, len)
Expand Down