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Auto merge of #86475 - crlf0710:miri_vtable_refactor, r=bjorn3
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Change vtable memory representation to use tcx allocated allocations.

This fixes #86324. However i suspect there's more to change before it can land.

r? `@bjorn3`
cc `@rust-lang/miri`
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bors committed Jun 29, 2021
2 parents 8971fff + 97772bb commit e98897e
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Showing 21 changed files with 150 additions and 249 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_cranelift/src/common.rs
Original file line number Diff line number Diff line change
Expand Up @@ -233,7 +233,7 @@ pub(crate) struct FunctionCx<'m, 'clif, 'tcx: 'm> {
pub(crate) module: &'m mut dyn Module,
pub(crate) tcx: TyCtxt<'tcx>,
pub(crate) pointer_type: Type, // Cached from module
pub(crate) vtables: FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), DataId>,
pub(crate) vtables: FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), Pointer>,
pub(crate) constants_cx: ConstantCx,

pub(crate) instance: Instance<'tcx>,
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_cranelift/src/constant.rs
Original file line number Diff line number Diff line change
Expand Up @@ -249,7 +249,7 @@ pub(crate) fn codegen_const_value<'tcx>(
}
}

fn pointer_for_allocation<'tcx>(
pub(crate) fn pointer_for_allocation<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
alloc: &'tcx Allocation,
) -> crate::pointer::Pointer {
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_cranelift/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ mod prelude {
pub(crate) use cranelift_codegen::isa::{self, CallConv};
pub(crate) use cranelift_codegen::Context;
pub(crate) use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
pub(crate) use cranelift_module::{self, DataContext, DataId, FuncId, Linkage, Module};
pub(crate) use cranelift_module::{self, DataContext, FuncId, Linkage, Module};

pub(crate) use crate::abi::*;
pub(crate) use crate::base::{codegen_operand, codegen_place};
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4 changes: 1 addition & 3 deletions compiler/rustc_codegen_cranelift/src/unsize.rs
Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,7 @@ pub(crate) fn unsized_info<'tcx>(
// change to the vtable.
old_info.expect("unsized_info: missing old info for trait upcast")
}
(_, &ty::Dynamic(ref data, ..)) => {
crate::vtable::get_vtable(fx, fx.layout_of(source), data.principal())
}
(_, &ty::Dynamic(ref data, ..)) => crate::vtable::get_vtable(fx, source, data.principal()),
_ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
}
}
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106 changes: 10 additions & 96 deletions compiler/rustc_codegen_cranelift/src/vtable.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
// FIXME dedup this logic between miri, cg_llvm and cg_clif

use crate::prelude::*;
use ty::VtblEntry;
use super::constant::pointer_for_allocation;

fn vtable_memflags() -> MemFlags {
let mut flags = MemFlags::trusted(); // A vtable access is always aligned and will never trap.
Expand Down Expand Up @@ -66,105 +66,19 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(

pub(crate) fn get_vtable<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
layout: TyAndLayout<'tcx>,
ty: Ty<'tcx>,
trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
) -> Value {
let data_id = if let Some(data_id) = fx.vtables.get(&(layout.ty, trait_ref)) {
*data_id
let vtable_ptr = if let Some(vtable_ptr) = fx.vtables.get(&(ty, trait_ref)) {
*vtable_ptr
} else {
let data_id = build_vtable(fx, layout, trait_ref);
fx.vtables.insert((layout.ty, trait_ref), data_id);
data_id
};

let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
}

fn build_vtable<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
layout: TyAndLayout<'tcx>,
trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
) -> DataId {
let tcx = fx.tcx;
let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
let vtable_alloc_id = fx.tcx.vtable_allocation(ty, trait_ref);
let vtable_allocation = fx.tcx.global_alloc(vtable_alloc_id).unwrap_memory();
let vtable_ptr = pointer_for_allocation(fx, vtable_allocation);

let drop_in_place_fn = import_function(
tcx,
fx.module,
Instance::resolve_drop_in_place(tcx, layout.ty).polymorphize(fx.tcx),
);

let vtable_entries = if let Some(trait_ref) = trait_ref {
tcx.vtable_entries(trait_ref.with_self_ty(tcx, layout.ty))
} else {
ty::COMMON_VTABLE_ENTRIES
fx.vtables.insert((ty, trait_ref), vtable_ptr);
vtable_ptr
};

let mut data_ctx = DataContext::new();
let mut data = ::std::iter::repeat(0u8)
.take(vtable_entries.len() * usize_size)
.collect::<Vec<u8>>()
.into_boxed_slice();

for (idx, entry) in vtable_entries.iter().enumerate() {
match entry {
VtblEntry::MetadataSize => {
write_usize(fx.tcx, &mut data, idx, layout.size.bytes());
}
VtblEntry::MetadataAlign => {
write_usize(fx.tcx, &mut data, idx, layout.align.abi.bytes());
}
VtblEntry::MetadataDropInPlace | VtblEntry::Vacant | VtblEntry::Method(_, _) => {}
}
}
data_ctx.define(data);

for (idx, entry) in vtable_entries.iter().enumerate() {
match entry {
VtblEntry::MetadataDropInPlace => {
let func_ref = fx.module.declare_func_in_data(drop_in_place_fn, &mut data_ctx);
data_ctx.write_function_addr((idx * usize_size) as u32, func_ref);
}
VtblEntry::Method(def_id, substs) => {
let func_id = import_function(
tcx,
fx.module,
Instance::resolve_for_vtable(tcx, ParamEnv::reveal_all(), *def_id, substs)
.unwrap()
.polymorphize(fx.tcx),
);
let func_ref = fx.module.declare_func_in_data(func_id, &mut data_ctx);
data_ctx.write_function_addr((idx * usize_size) as u32, func_ref);
}
VtblEntry::MetadataSize | VtblEntry::MetadataAlign | VtblEntry::Vacant => {}
}
}

data_ctx.set_align(fx.tcx.data_layout.pointer_align.pref.bytes());

let data_id = fx.module.declare_anonymous_data(false, false).unwrap();

fx.module.define_data(data_id, &data_ctx).unwrap();

data_id
}

fn write_usize(tcx: TyCtxt<'_>, buf: &mut [u8], idx: usize, num: u64) {
let pointer_size =
tcx.layout_of(ParamEnv::reveal_all().and(tcx.types.usize)).unwrap().size.bytes() as usize;
let target = &mut buf[idx * pointer_size..(idx + 1) * pointer_size];

match tcx.data_layout.endian {
rustc_target::abi::Endian::Little => match pointer_size {
4 => target.copy_from_slice(&(num as u32).to_le_bytes()),
8 => target.copy_from_slice(&(num as u64).to_le_bytes()),
_ => todo!("pointer size {} is not yet supported", pointer_size),
},
rustc_target::abi::Endian::Big => match pointer_size {
4 => target.copy_from_slice(&(num as u32).to_be_bytes()),
8 => target.copy_from_slice(&(num as u64).to_be_bytes()),
_ => todo!("pointer size {} is not yet supported", pointer_size),
},
}
vtable_ptr.get_addr(fx)
}
4 changes: 4 additions & 0 deletions compiler/rustc_codegen_llvm/src/common.rs
Original file line number Diff line number Diff line change
Expand Up @@ -282,6 +282,10 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
}

fn const_data_from_alloc(&self, alloc: &Allocation) -> Self::Value {
const_alloc_to_llvm(self, alloc)
}

fn from_const_alloc(
&self,
layout: TyAndLayout<'tcx>,
Expand Down
43 changes: 4 additions & 39 deletions compiler/rustc_codegen_ssa/src/meth.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
use crate::traits::*;

use rustc_middle::ty::{self, Instance, Ty, VtblEntry, COMMON_VTABLE_ENTRIES};
use rustc_middle::ty::{self, Ty};
use rustc_target::abi::call::FnAbi;

#[derive(Copy, Clone, Debug)]
Expand Down Expand Up @@ -70,48 +70,13 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
return val;
}

// Not in the cache; build it.
let nullptr = cx.const_null(cx.type_i8p_ext(cx.data_layout().instruction_address_space));

let vtable_entries = if let Some(trait_ref) = trait_ref {
tcx.vtable_entries(trait_ref.with_self_ty(tcx, ty))
} else {
COMMON_VTABLE_ENTRIES
};

let layout = cx.layout_of(ty);
// /////////////////////////////////////////////////////////////////////////////////////////////
// If you touch this code, be sure to also make the corresponding changes to
// `get_vtable` in `rust_mir/interpret/traits.rs`.
// /////////////////////////////////////////////////////////////////////////////////////////////
let components: Vec<_> = vtable_entries
.iter()
.map(|entry| match entry {
VtblEntry::MetadataDropInPlace => {
cx.get_fn_addr(Instance::resolve_drop_in_place(cx.tcx(), ty))
}
VtblEntry::MetadataSize => cx.const_usize(layout.size.bytes()),
VtblEntry::MetadataAlign => cx.const_usize(layout.align.abi.bytes()),
VtblEntry::Vacant => nullptr,
VtblEntry::Method(def_id, substs) => cx.get_fn_addr(
ty::Instance::resolve_for_vtable(
cx.tcx(),
ty::ParamEnv::reveal_all(),
*def_id,
substs,
)
.unwrap()
.polymorphize(cx.tcx()),
),
})
.collect();

let vtable_const = cx.const_struct(&components, false);
let vtable_alloc_id = tcx.vtable_allocation(ty, trait_ref);
let vtable_allocation = tcx.global_alloc(vtable_alloc_id).unwrap_memory();
let vtable_const = cx.const_data_from_alloc(vtable_allocation);
let align = cx.data_layout().pointer_align.abi;
let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));

cx.create_vtable_metadata(ty, vtable);

cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
vtable
}
2 changes: 2 additions & 0 deletions compiler/rustc_codegen_ssa/src/traits/consts.rs
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ pub trait ConstMethods<'tcx>: BackendTypes {
fn const_to_opt_uint(&self, v: Self::Value) -> Option<u64>;
fn const_to_opt_u128(&self, v: Self::Value, sign_ext: bool) -> Option<u128>;

fn const_data_from_alloc(&self, alloc: &Allocation) -> Self::Value;

fn scalar_to_backend(&self, cv: Scalar, layout: &abi::Scalar, llty: Self::Type) -> Self::Value;
fn from_const_alloc(
&self,
Expand Down
6 changes: 5 additions & 1 deletion compiler/rustc_middle/src/ty/context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ use crate::middle;
use crate::middle::cstore::{CrateStoreDyn, EncodedMetadata};
use crate::middle::resolve_lifetime::{self, LifetimeScopeForPath, ObjectLifetimeDefault};
use crate::middle::stability;
use crate::mir::interpret::{self, Allocation, ConstValue, Scalar};
use crate::mir::interpret::{self, AllocId, Allocation, ConstValue, Scalar};
use crate::mir::{Body, Field, Local, Place, PlaceElem, ProjectionKind, Promoted};
use crate::thir::Thir;
use crate::traits;
Expand Down Expand Up @@ -1044,6 +1044,9 @@ pub struct GlobalCtxt<'tcx> {
output_filenames: Arc<OutputFilenames>,

pub main_def: Option<MainDefinition>,

pub(super) vtables_cache:
Lock<FxHashMap<(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), AllocId>>,
}

impl<'tcx> TyCtxt<'tcx> {
Expand Down Expand Up @@ -1201,6 +1204,7 @@ impl<'tcx> TyCtxt<'tcx> {
alloc_map: Lock::new(interpret::AllocMap::new()),
output_filenames: Arc::new(output_filenames),
main_def: resolutions.main_def,
vtables_cache: Default::default(),
}
}

Expand Down
18 changes: 2 additions & 16 deletions compiler/rustc_middle/src/ty/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ pub use adt::*;
pub use assoc::*;
pub use closure::*;
pub use generics::*;
pub use vtable::*;

use crate::hir::exports::ExportMap;
use crate::ich::StableHashingContext;
Expand Down Expand Up @@ -94,6 +95,7 @@ pub mod relate;
pub mod subst;
pub mod trait_def;
pub mod util;
pub mod vtable;
pub mod walk;

mod adt;
Expand Down Expand Up @@ -2009,19 +2011,3 @@ impl<'tcx> fmt::Debug for SymbolName<'tcx> {
fmt::Display::fmt(&self.name, fmt)
}
}

#[derive(Clone, Copy, Debug, PartialEq, HashStable)]
pub enum VtblEntry<'tcx> {
MetadataDropInPlace,
MetadataSize,
MetadataAlign,
Vacant,
Method(DefId, SubstsRef<'tcx>),
}

pub const COMMON_VTABLE_ENTRIES: &[VtblEntry<'_>] =
&[VtblEntry::MetadataDropInPlace, VtblEntry::MetadataSize, VtblEntry::MetadataAlign];

pub const COMMON_VTABLE_ENTRIES_DROPINPLACE: usize = 0;
pub const COMMON_VTABLE_ENTRIES_SIZE: usize = 1;
pub const COMMON_VTABLE_ENTRIES_ALIGN: usize = 2;
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