556 lines
23 KiB
Rust
556 lines
23 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//!
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//
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// Code relating to drop glue.
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use back::abi;
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use back::link::*;
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use llvm;
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use llvm::{ValueRef, get_param};
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use metadata::csearch;
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use middle::lang_items::ExchangeFreeFnLangItem;
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use middle::subst;
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use middle::subst::{Subst, Substs};
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use middle::ty::{self, Ty};
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use trans::adt;
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use trans::adt::GetDtorType; // for tcx.dtor_type()
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use trans::base::*;
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use trans::build::*;
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use trans::callee;
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use trans::cleanup;
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use trans::cleanup::CleanupMethods;
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use trans::common::*;
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use trans::debuginfo::DebugLoc;
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use trans::declare;
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use trans::expr;
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use trans::foreign;
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use trans::inline;
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use trans::machine::*;
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use trans::monomorphize;
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use trans::type_of::{type_of, type_of_dtor, sizing_type_of, align_of};
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use trans::type_::Type;
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use arena::TypedArena;
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use libc::c_uint;
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use syntax::ast;
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pub fn trans_exchange_free_dyn<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
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v: ValueRef,
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size: ValueRef,
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align: ValueRef,
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debug_loc: DebugLoc)
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-> Block<'blk, 'tcx> {
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let _icx = push_ctxt("trans_exchange_free");
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let ccx = cx.ccx();
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callee::trans_lang_call(cx,
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langcall(cx, None, "", ExchangeFreeFnLangItem),
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&[PointerCast(cx, v, Type::i8p(ccx)), size, align],
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Some(expr::Ignore),
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debug_loc).bcx
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}
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pub fn trans_exchange_free<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
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v: ValueRef,
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size: u64,
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align: u32,
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debug_loc: DebugLoc)
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-> Block<'blk, 'tcx> {
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trans_exchange_free_dyn(cx,
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v,
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C_uint(cx.ccx(), size),
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C_uint(cx.ccx(), align),
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debug_loc)
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}
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pub fn trans_exchange_free_ty<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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ptr: ValueRef,
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content_ty: Ty<'tcx>,
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debug_loc: DebugLoc)
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-> Block<'blk, 'tcx> {
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assert!(type_is_sized(bcx.ccx().tcx(), content_ty));
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let sizing_type = sizing_type_of(bcx.ccx(), content_ty);
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let content_size = llsize_of_alloc(bcx.ccx(), sizing_type);
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// `Box<ZeroSizeType>` does not allocate.
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if content_size != 0 {
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let content_align = align_of(bcx.ccx(), content_ty);
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trans_exchange_free(bcx, ptr, content_size, content_align, debug_loc)
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} else {
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bcx
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}
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}
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pub fn get_drop_glue_type<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
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t: Ty<'tcx>) -> Ty<'tcx> {
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let tcx = ccx.tcx();
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// Even if there is no dtor for t, there might be one deeper down and we
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// might need to pass in the vtable ptr.
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if !type_is_sized(tcx, t) {
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return t
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}
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// FIXME (#22815): note that type_needs_drop conservatively
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// approximates in some cases and may say a type expression
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// requires drop glue when it actually does not.
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//
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// (In this case it is not clear whether any harm is done, i.e.
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// erroneously returning `t` in some cases where we could have
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// returned `tcx.types.i8` does not appear unsound. The impact on
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// code quality is unknown at this time.)
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if !type_needs_drop(tcx, t) {
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return tcx.types.i8;
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}
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match t.sty {
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ty::TyBox(typ) if !type_needs_drop(tcx, typ)
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&& type_is_sized(tcx, typ) => {
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let llty = sizing_type_of(ccx, typ);
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// `Box<ZeroSizeType>` does not allocate.
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if llsize_of_alloc(ccx, llty) == 0 {
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tcx.types.i8
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} else {
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t
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}
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}
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_ => t
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}
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}
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pub fn drop_ty<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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v: ValueRef,
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t: Ty<'tcx>,
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debug_loc: DebugLoc) -> Block<'blk, 'tcx> {
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drop_ty_core(bcx, v, t, debug_loc, false)
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}
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pub fn drop_ty_core<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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v: ValueRef,
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t: Ty<'tcx>,
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debug_loc: DebugLoc,
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skip_dtor: bool) -> Block<'blk, 'tcx> {
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// NB: v is an *alias* of type t here, not a direct value.
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debug!("drop_ty_core(t={:?}, skip_dtor={})", t, skip_dtor);
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let _icx = push_ctxt("drop_ty");
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if bcx.fcx.type_needs_drop(t) {
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let ccx = bcx.ccx();
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let g = if skip_dtor {
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DropGlueKind::TyContents(t)
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} else {
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DropGlueKind::Ty(t)
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};
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let glue = get_drop_glue_core(ccx, g);
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let glue_type = get_drop_glue_type(ccx, t);
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let ptr = if glue_type != t {
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PointerCast(bcx, v, type_of(ccx, glue_type).ptr_to())
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} else {
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v
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};
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Call(bcx, glue, &[ptr], None, debug_loc);
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}
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bcx
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}
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pub fn drop_ty_immediate<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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v: ValueRef,
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t: Ty<'tcx>,
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debug_loc: DebugLoc,
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skip_dtor: bool)
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-> Block<'blk, 'tcx> {
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let _icx = push_ctxt("drop_ty_immediate");
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let vp = alloca(bcx, type_of(bcx.ccx(), t), "");
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store_ty(bcx, v, vp, t);
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drop_ty_core(bcx, vp, t, debug_loc, skip_dtor)
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}
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pub fn get_drop_glue<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) -> ValueRef {
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get_drop_glue_core(ccx, DropGlueKind::Ty(t))
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}
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub enum DropGlueKind<'tcx> {
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/// The normal path; runs the dtor, and then recurs on the contents
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Ty(Ty<'tcx>),
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/// Skips the dtor, if any, for ty; drops the contents directly.
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/// Note that the dtor is only skipped at the most *shallow*
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/// level, namely, an `impl Drop for Ty` itself. So, for example,
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/// if Ty is Newtype(S) then only the Drop impl for for Newtype
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/// itself will be skipped, while the Drop impl for S, if any,
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/// will be invoked.
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TyContents(Ty<'tcx>),
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}
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impl<'tcx> DropGlueKind<'tcx> {
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fn ty(&self) -> Ty<'tcx> {
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match *self { DropGlueKind::Ty(t) | DropGlueKind::TyContents(t) => t }
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}
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fn map_ty<F>(&self, mut f: F) -> DropGlueKind<'tcx> where F: FnMut(Ty<'tcx>) -> Ty<'tcx>
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{
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match *self {
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DropGlueKind::Ty(t) => DropGlueKind::Ty(f(t)),
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DropGlueKind::TyContents(t) => DropGlueKind::TyContents(f(t)),
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}
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}
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}
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fn get_drop_glue_core<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
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g: DropGlueKind<'tcx>) -> ValueRef {
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debug!("make drop glue for {:?}", g);
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let g = g.map_ty(|t| get_drop_glue_type(ccx, t));
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debug!("drop glue type {:?}", g);
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match ccx.drop_glues().borrow().get(&g) {
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Some(&glue) => return glue,
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_ => { }
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}
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let t = g.ty();
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let llty = if type_is_sized(ccx.tcx(), t) {
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type_of(ccx, t).ptr_to()
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} else {
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type_of(ccx, ccx.tcx().mk_box(t)).ptr_to()
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};
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let llfnty = Type::glue_fn(ccx, llty);
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// To avoid infinite recursion, don't `make_drop_glue` until after we've
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// added the entry to the `drop_glues` cache.
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if let Some(old_sym) = ccx.available_drop_glues().borrow().get(&g) {
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let llfn = declare::declare_cfn(ccx, &old_sym, llfnty, ccx.tcx().mk_nil());
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ccx.drop_glues().borrow_mut().insert(g, llfn);
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return llfn;
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};
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let fn_nm = mangle_internal_name_by_type_and_seq(ccx, t, "drop");
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let llfn = declare::define_cfn(ccx, &fn_nm, llfnty, ccx.tcx().mk_nil()).unwrap_or_else(||{
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ccx.sess().bug(&format!("symbol `{}` already defined", fn_nm));
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});
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ccx.available_drop_glues().borrow_mut().insert(g, fn_nm);
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let _s = StatRecorder::new(ccx, format!("drop {:?}", t));
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let empty_substs = ccx.tcx().mk_substs(Substs::trans_empty());
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let (arena, fcx): (TypedArena<_>, FunctionContext);
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arena = TypedArena::new();
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fcx = new_fn_ctxt(ccx, llfn, ast::DUMMY_NODE_ID, false,
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ty::FnConverging(ccx.tcx().mk_nil()),
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empty_substs, None, &arena);
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let bcx = init_function(&fcx, false, ty::FnConverging(ccx.tcx().mk_nil()));
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update_linkage(ccx, llfn, None, OriginalTranslation);
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ccx.stats().n_glues_created.set(ccx.stats().n_glues_created.get() + 1);
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// All glue functions take values passed *by alias*; this is a
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// requirement since in many contexts glue is invoked indirectly and
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// the caller has no idea if it's dealing with something that can be
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// passed by value.
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//
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// llfn is expected be declared to take a parameter of the appropriate
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// type, so we don't need to explicitly cast the function parameter.
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let llrawptr0 = get_param(llfn, fcx.arg_offset() as c_uint);
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let bcx = make_drop_glue(bcx, llrawptr0, g);
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finish_fn(&fcx, bcx, ty::FnConverging(ccx.tcx().mk_nil()), DebugLoc::None);
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llfn
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}
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fn trans_struct_drop_flag<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
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t: Ty<'tcx>,
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struct_data: ValueRef,
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dtor_did: ast::DefId,
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class_did: ast::DefId,
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substs: &subst::Substs<'tcx>)
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-> Block<'blk, 'tcx> {
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assert!(type_is_sized(bcx.tcx(), t), "Precondition: caller must ensure t is sized");
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let repr = adt::represent_type(bcx.ccx(), t);
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let drop_flag = unpack_datum!(bcx, adt::trans_drop_flag_ptr(bcx, &*repr, struct_data));
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let loaded = load_ty(bcx, drop_flag.val, bcx.tcx().dtor_type());
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let drop_flag_llty = type_of(bcx.fcx.ccx, bcx.tcx().dtor_type());
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let init_val = C_integral(drop_flag_llty, adt::DTOR_NEEDED as u64, false);
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let bcx = if !bcx.ccx().check_drop_flag_for_sanity() {
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bcx
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} else {
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let drop_flag_llty = type_of(bcx.fcx.ccx, bcx.tcx().dtor_type());
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let done_val = C_integral(drop_flag_llty, adt::DTOR_DONE as u64, false);
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let not_init = ICmp(bcx, llvm::IntNE, loaded, init_val, DebugLoc::None);
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let not_done = ICmp(bcx, llvm::IntNE, loaded, done_val, DebugLoc::None);
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let drop_flag_neither_initialized_nor_cleared =
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And(bcx, not_init, not_done, DebugLoc::None);
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with_cond(bcx, drop_flag_neither_initialized_nor_cleared, |cx| {
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let llfn = cx.ccx().get_intrinsic(&("llvm.debugtrap"));
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Call(cx, llfn, &[], None, DebugLoc::None);
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cx
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})
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};
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let drop_flag_dtor_needed = ICmp(bcx, llvm::IntEQ, loaded, init_val, DebugLoc::None);
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with_cond(bcx, drop_flag_dtor_needed, |cx| {
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trans_struct_drop(cx, t, struct_data, dtor_did, class_did, substs)
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})
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}
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pub fn get_res_dtor<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
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did: ast::DefId,
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t: Ty<'tcx>,
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parent_id: ast::DefId,
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substs: &Substs<'tcx>)
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-> ValueRef {
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let _icx = push_ctxt("trans_res_dtor");
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let did = inline::maybe_instantiate_inline(ccx, did);
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if !substs.types.is_empty() {
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assert_eq!(did.krate, ast::LOCAL_CRATE);
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// Since we're in trans we don't care for any region parameters
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let substs = ccx.tcx().mk_substs(Substs::erased(substs.types.clone()));
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let (val, _, _) = monomorphize::monomorphic_fn(ccx, did, substs, None);
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val
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} else if did.krate == ast::LOCAL_CRATE {
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get_item_val(ccx, did.node)
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} else {
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let tcx = ccx.tcx();
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let name = csearch::get_symbol(&ccx.sess().cstore, did);
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let class_ty = tcx.lookup_item_type(parent_id).ty.subst(tcx, substs);
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let llty = type_of_dtor(ccx, class_ty);
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let dtor_ty = ccx.tcx().mk_ctor_fn(did,
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&[get_drop_glue_type(ccx, t)],
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ccx.tcx().mk_nil());
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foreign::get_extern_fn(ccx, &mut *ccx.externs().borrow_mut(), &name[..], llvm::CCallConv,
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llty, dtor_ty)
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}
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}
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fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
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t: Ty<'tcx>,
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v0: ValueRef,
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dtor_did: ast::DefId,
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class_did: ast::DefId,
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substs: &subst::Substs<'tcx>)
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-> Block<'blk, 'tcx>
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{
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debug!("trans_struct_drop t: {}", t);
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// Find and call the actual destructor
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let dtor_addr = get_res_dtor(bcx.ccx(), dtor_did, t, class_did, substs);
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// Class dtors have no explicit args, so the params should
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// just consist of the environment (self).
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let params = unsafe {
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let ty = Type::from_ref(llvm::LLVMTypeOf(dtor_addr));
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ty.element_type().func_params()
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};
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assert_eq!(params.len(), if type_is_sized(bcx.tcx(), t) { 1 } else { 2 });
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// Be sure to put the contents into a scope so we can use an invoke
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// instruction to call the user destructor but still call the field
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// destructors if the user destructor panics.
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//
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// FIXME (#14875) panic-in-drop semantics might be unsupported; we
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// might well consider changing below to more direct code.
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let contents_scope = bcx.fcx.push_custom_cleanup_scope();
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// Issue #23611: schedule cleanup of contents, re-inspecting the
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// discriminant (if any) in case of variant swap in drop code.
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bcx.fcx.schedule_drop_adt_contents(cleanup::CustomScope(contents_scope), v0, t);
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let glue_type = get_drop_glue_type(bcx.ccx(), t);
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let dtor_ty = bcx.tcx().mk_ctor_fn(class_did, &[glue_type], bcx.tcx().mk_nil());
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let (_, bcx) = if type_is_sized(bcx.tcx(), t) {
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invoke(bcx, dtor_addr, &[v0], dtor_ty, DebugLoc::None)
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} else {
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let args = [Load(bcx, expr::get_dataptr(bcx, v0)), Load(bcx, expr::get_len(bcx, v0))];
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invoke(bcx, dtor_addr, &args, dtor_ty, DebugLoc::None)
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};
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bcx.fcx.pop_and_trans_custom_cleanup_scope(bcx, contents_scope)
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}
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pub fn size_and_align_of_dst<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, t: Ty<'tcx>, info: ValueRef)
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-> (ValueRef, ValueRef) {
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debug!("calculate size of DST: {}; with lost info: {}",
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t, bcx.val_to_string(info));
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if type_is_sized(bcx.tcx(), t) {
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let sizing_type = sizing_type_of(bcx.ccx(), t);
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let size = C_uint(bcx.ccx(), llsize_of_alloc(bcx.ccx(), sizing_type));
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let align = C_uint(bcx.ccx(), align_of(bcx.ccx(), t));
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return (size, align);
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}
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match t.sty {
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ty::TyStruct(id, substs) => {
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let ccx = bcx.ccx();
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// First get the size of all statically known fields.
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// Don't use type_of::sizing_type_of because that expects t to be sized.
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assert!(!t.is_simd(bcx.tcx()));
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let repr = adt::represent_type(ccx, t);
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let sizing_type = adt::sizing_type_of(ccx, &*repr, true);
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let sized_size = C_uint(ccx, llsize_of_alloc(ccx, sizing_type));
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let sized_align = C_uint(ccx, llalign_of_min(ccx, sizing_type));
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// Recurse to get the size of the dynamically sized field (must be
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// the last field).
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let fields = bcx.tcx().struct_fields(id, substs);
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let last_field = fields[fields.len()-1];
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let field_ty = last_field.mt.ty;
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let (unsized_size, unsized_align) = size_and_align_of_dst(bcx, field_ty, info);
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// Return the sum of sizes and max of aligns.
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let size = Add(bcx, sized_size, unsized_size, DebugLoc::None);
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let align = Select(bcx,
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ICmp(bcx,
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llvm::IntULT,
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sized_align,
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unsized_align,
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DebugLoc::None),
|
|
sized_align,
|
|
unsized_align);
|
|
(size, align)
|
|
}
|
|
ty::TyTrait(..) => {
|
|
// info points to the vtable and the second entry in the vtable is the
|
|
// dynamic size of the object.
|
|
let info = PointerCast(bcx, info, Type::int(bcx.ccx()).ptr_to());
|
|
let size_ptr = GEPi(bcx, info, &[1]);
|
|
let align_ptr = GEPi(bcx, info, &[2]);
|
|
(Load(bcx, size_ptr), Load(bcx, align_ptr))
|
|
}
|
|
ty::TySlice(_) | ty::TyStr => {
|
|
let unit_ty = t.sequence_element_type(bcx.tcx());
|
|
// The info in this case is the length of the str, so the size is that
|
|
// times the unit size.
|
|
let llunit_ty = sizing_type_of(bcx.ccx(), unit_ty);
|
|
let unit_align = llalign_of_min(bcx.ccx(), llunit_ty);
|
|
let unit_size = llsize_of_alloc(bcx.ccx(), llunit_ty);
|
|
(Mul(bcx, info, C_uint(bcx.ccx(), unit_size), DebugLoc::None),
|
|
C_uint(bcx.ccx(), unit_align))
|
|
}
|
|
_ => bcx.sess().bug(&format!("Unexpected unsized type, found {}", t))
|
|
}
|
|
}
|
|
|
|
fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, g: DropGlueKind<'tcx>)
|
|
-> Block<'blk, 'tcx> {
|
|
let t = g.ty();
|
|
let skip_dtor = match g { DropGlueKind::Ty(_) => false, DropGlueKind::TyContents(_) => true };
|
|
// NB: v0 is an *alias* of type t here, not a direct value.
|
|
let _icx = push_ctxt("make_drop_glue");
|
|
|
|
// Only drop the value when it ... well, we used to check for
|
|
// non-null, (and maybe we need to continue doing so), but we now
|
|
// must definitely check for special bit-patterns corresponding to
|
|
// the special dtor markings.
|
|
|
|
let inttype = Type::int(bcx.ccx());
|
|
let dropped_pattern = C_integral(inttype, adt::dtor_done_usize(bcx.fcx.ccx) as u64, false);
|
|
|
|
match t.sty {
|
|
ty::TyBox(content_ty) => {
|
|
// Support for TyBox is built-in and its drop glue is
|
|
// special. It may move to library and have Drop impl. As
|
|
// a safe-guard, assert TyBox not used with TyContents.
|
|
assert!(!skip_dtor);
|
|
if !type_is_sized(bcx.tcx(), content_ty) {
|
|
let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
|
|
let llbox = Load(bcx, llval);
|
|
let llbox_as_usize = PtrToInt(bcx, llbox, Type::int(bcx.ccx()));
|
|
let drop_flag_not_dropped_already =
|
|
ICmp(bcx, llvm::IntNE, llbox_as_usize, dropped_pattern, DebugLoc::None);
|
|
with_cond(bcx, drop_flag_not_dropped_already, |bcx| {
|
|
let bcx = drop_ty(bcx, v0, content_ty, DebugLoc::None);
|
|
let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
|
|
let info = Load(bcx, info);
|
|
let (llsize, llalign) = size_and_align_of_dst(bcx, content_ty, info);
|
|
|
|
// `Box<ZeroSizeType>` does not allocate.
|
|
let needs_free = ICmp(bcx,
|
|
llvm::IntNE,
|
|
llsize,
|
|
C_uint(bcx.ccx(), 0u64),
|
|
DebugLoc::None);
|
|
with_cond(bcx, needs_free, |bcx| {
|
|
trans_exchange_free_dyn(bcx, llbox, llsize, llalign, DebugLoc::None)
|
|
})
|
|
})
|
|
} else {
|
|
let llval = v0;
|
|
let llbox = Load(bcx, llval);
|
|
let llbox_as_usize = PtrToInt(bcx, llbox, inttype);
|
|
let drop_flag_not_dropped_already =
|
|
ICmp(bcx, llvm::IntNE, llbox_as_usize, dropped_pattern, DebugLoc::None);
|
|
with_cond(bcx, drop_flag_not_dropped_already, |bcx| {
|
|
let bcx = drop_ty(bcx, llbox, content_ty, DebugLoc::None);
|
|
trans_exchange_free_ty(bcx, llbox, content_ty, DebugLoc::None)
|
|
})
|
|
}
|
|
}
|
|
ty::TyStruct(did, substs) | ty::TyEnum(did, substs) => {
|
|
let tcx = bcx.tcx();
|
|
match (tcx.ty_dtor(did), skip_dtor) {
|
|
(ty::TraitDtor(dtor, true), false) => {
|
|
// FIXME(16758) Since the struct is unsized, it is hard to
|
|
// find the drop flag (which is at the end of the struct).
|
|
// Lets just ignore the flag and pretend everything will be
|
|
// OK.
|
|
if type_is_sized(bcx.tcx(), t) {
|
|
trans_struct_drop_flag(bcx, t, v0, dtor, did, substs)
|
|
} else {
|
|
// Give the user a heads up that we are doing something
|
|
// stupid and dangerous.
|
|
bcx.sess().warn(&format!("Ignoring drop flag in destructor for {}\
|
|
because the struct is unsized. See issue\
|
|
#16758", t));
|
|
trans_struct_drop(bcx, t, v0, dtor, did, substs)
|
|
}
|
|
}
|
|
(ty::TraitDtor(dtor, false), false) => {
|
|
trans_struct_drop(bcx, t, v0, dtor, did, substs)
|
|
}
|
|
(ty::NoDtor, _) | (_, true) => {
|
|
// No dtor? Just the default case
|
|
iter_structural_ty(bcx, v0, t, |bb, vv, tt| drop_ty(bb, vv, tt, DebugLoc::None))
|
|
}
|
|
}
|
|
}
|
|
ty::TyTrait(..) => {
|
|
// No support in vtable for distinguishing destroying with
|
|
// versus without calling Drop::drop. Assert caller is
|
|
// okay with always calling the Drop impl, if any.
|
|
assert!(!skip_dtor);
|
|
let data_ptr = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
|
|
let vtable_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
|
|
let dtor = Load(bcx, vtable_ptr);
|
|
Call(bcx,
|
|
dtor,
|
|
&[PointerCast(bcx, Load(bcx, data_ptr), Type::i8p(bcx.ccx()))],
|
|
None,
|
|
DebugLoc::None);
|
|
bcx
|
|
}
|
|
_ => {
|
|
if bcx.fcx.type_needs_drop(t) {
|
|
iter_structural_ty(bcx,
|
|
v0,
|
|
t,
|
|
|bb, vv, tt| drop_ty(bb, vv, tt, DebugLoc::None))
|
|
} else {
|
|
bcx
|
|
}
|
|
}
|
|
}
|
|
}
|