502 lines
17 KiB
Rust
502 lines
17 KiB
Rust
// Copyright 2012 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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use back::abi;
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use back::link::{mangle_internal_name_by_path_and_seq};
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use lib::llvm::ValueRef;
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use middle::moves;
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use middle::trans::base::*;
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use middle::trans::build::*;
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use middle::trans::common::*;
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use middle::trans::datum::{Datum, INIT};
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use middle::trans::debuginfo;
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use middle::trans::expr;
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use middle::trans::glue;
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use middle::trans::type_of::*;
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use middle::ty;
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use util::ppaux::ty_to_str;
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use std::vec;
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use syntax::ast;
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use syntax::ast_map::path_name;
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use syntax::ast_util;
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use syntax::parse::token::special_idents;
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// ___Good to know (tm)__________________________________________________
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//
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// The layout of a closure environment in memory is
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// roughly as follows:
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//
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// struct rust_opaque_box { // see rust_internal.h
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// unsigned ref_count; // only used for @fn()
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// type_desc *tydesc; // describes closure_data struct
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// rust_opaque_box *prev; // (used internally by memory alloc)
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// rust_opaque_box *next; // (used internally by memory alloc)
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// struct closure_data {
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// type_desc *bound_tdescs[]; // bound descriptors
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// struct {
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// upvar1_t upvar1;
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// ...
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// upvarN_t upvarN;
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// } bound_data;
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// }
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// };
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//
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// Note that the closure is itself a rust_opaque_box. This is true
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// even for ~fn and &fn, because we wish to keep binary compatibility
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// between all kinds of closures. The allocation strategy for this
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// closure depends on the closure type. For a sendfn, the closure
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// (and the referenced type descriptors) will be allocated in the
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// exchange heap. For a fn, the closure is allocated in the task heap
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// and is reference counted. For a block, the closure is allocated on
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// the stack.
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//
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// ## Opaque closures and the embedded type descriptor ##
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//
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// One interesting part of closures is that they encapsulate the data
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// that they close over. So when I have a ptr to a closure, I do not
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// know how many type descriptors it contains nor what upvars are
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// captured within. That means I do not know precisely how big it is
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// nor where its fields are located. This is called an "opaque
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// closure".
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//
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// Typically an opaque closure suffices because we only manipulate it
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// by ptr. The routine Type::opaque_box().ptr_to() returns an
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// appropriate type for such an opaque closure; it allows access to
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// the box fields, but not the closure_data itself.
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//
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// But sometimes, such as when cloning or freeing a closure, we need
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// to know the full information. That is where the type descriptor
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// that defines the closure comes in handy. We can use its take and
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// drop glue functions to allocate/free data as needed.
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//
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// ## Subtleties concerning alignment ##
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//
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// It is important that we be able to locate the closure data *without
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// knowing the kind of data that is being bound*. This can be tricky
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// because the alignment requirements of the bound data affects the
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// alignment requires of the closure_data struct as a whole. However,
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// right now this is a non-issue in any case, because the size of the
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// rust_opaque_box header is always a mutiple of 16-bytes, which is
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// the maximum alignment requirement we ever have to worry about.
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//
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// The only reason alignment matters is that, in order to learn what data
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// is bound, we would normally first load the type descriptors: but their
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// location is ultimately depend on their content! There is, however, a
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// workaround. We can load the tydesc from the rust_opaque_box, which
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// describes the closure_data struct and has self-contained derived type
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// descriptors, and read the alignment from there. It's just annoying to
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// do. Hopefully should this ever become an issue we'll have monomorphized
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// and type descriptors will all be a bad dream.
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//
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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pub enum EnvAction {
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/// Copy the value from this llvm ValueRef into the environment.
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EnvCopy,
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/// Move the value from this llvm ValueRef into the environment.
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EnvMove,
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/// Access by reference (used for stack closures).
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EnvRef
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}
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pub struct EnvValue {
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action: EnvAction,
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datum: Datum
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}
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impl EnvAction {
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pub fn to_str(&self) -> ~str {
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match *self {
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EnvCopy => ~"EnvCopy",
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EnvMove => ~"EnvMove",
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EnvRef => ~"EnvRef"
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}
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}
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}
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impl EnvValue {
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pub fn to_str(&self, ccx: &CrateContext) -> ~str {
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format!("{}({})", self.action.to_str(), self.datum.to_str(ccx))
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}
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}
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pub fn mk_tuplified_uniq_cbox_ty(tcx: ty::ctxt, cdata_ty: ty::t) -> ty::t {
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let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
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return ty::mk_imm_uniq(tcx, cbox_ty);
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}
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// Given a closure ty, emits a corresponding tuple ty
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pub fn mk_closure_tys(tcx: ty::ctxt,
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bound_values: &[EnvValue])
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-> ty::t {
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// determine the types of the values in the env. Note that this
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// is the actual types that will be stored in the map, not the
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// logical types as the user sees them, so by-ref upvars must be
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// converted to ptrs.
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let bound_tys = bound_values.map(|bv| {
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match bv.action {
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EnvCopy | EnvMove => bv.datum.ty,
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EnvRef => ty::mk_mut_ptr(tcx, bv.datum.ty)
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}
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});
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let cdata_ty = ty::mk_tup(tcx, bound_tys);
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debug2!("cdata_ty={}", ty_to_str(tcx, cdata_ty));
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return cdata_ty;
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}
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fn heap_for_unique_closure(bcx: @mut Block, t: ty::t) -> heap {
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if ty::type_contents(bcx.tcx(), t).contains_managed() {
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heap_managed_unique
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} else {
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heap_exchange_closure
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}
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}
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pub fn allocate_cbox(bcx: @mut Block, sigil: ast::Sigil, cdata_ty: ty::t)
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-> Result {
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let _icx = push_ctxt("closure::allocate_cbox");
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let ccx = bcx.ccx();
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let tcx = ccx.tcx;
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// Allocate and initialize the box:
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match sigil {
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ast::ManagedSigil => {
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tcx.sess.bug("trying to trans allocation of @fn")
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}
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ast::OwnedSigil => {
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malloc_raw(bcx, cdata_ty, heap_for_unique_closure(bcx, cdata_ty))
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}
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ast::BorrowedSigil => {
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let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
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let llbox = alloc_ty(bcx, cbox_ty, "__closure");
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rslt(bcx, llbox)
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}
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}
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}
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pub struct ClosureResult {
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llbox: ValueRef, // llvalue of ptr to closure
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cdata_ty: ty::t, // type of the closure data
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bcx: @mut Block // final bcx
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}
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// Given a block context and a list of tydescs and values to bind
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// construct a closure out of them. If copying is true, it is a
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// heap allocated closure that copies the upvars into environment.
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// Otherwise, it is stack allocated and copies pointers to the upvars.
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pub fn store_environment(bcx: @mut Block,
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bound_values: ~[EnvValue],
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sigil: ast::Sigil)
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-> ClosureResult {
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let _icx = push_ctxt("closure::store_environment");
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let ccx = bcx.ccx();
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let tcx = ccx.tcx;
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// compute the type of the closure
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let cdata_ty = mk_closure_tys(tcx, bound_values);
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// cbox_ty has the form of a tuple: (a, b, c) we want a ptr to a
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// tuple. This could be a ptr in uniq or a box or on stack,
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// whatever.
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let cbox_ty = tuplify_box_ty(tcx, cdata_ty);
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let cboxptr_ty = ty::mk_ptr(tcx, ty::mt {ty:cbox_ty, mutbl:ast::MutImmutable});
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let llboxptr_ty = type_of(ccx, cboxptr_ty);
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// If there are no bound values, no point in allocating anything.
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if bound_values.is_empty() {
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return ClosureResult {llbox: C_null(llboxptr_ty),
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cdata_ty: cdata_ty,
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bcx: bcx};
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}
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// allocate closure in the heap
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let Result {bcx: bcx, val: llbox} = allocate_cbox(bcx, sigil, cdata_ty);
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let llbox = PointerCast(bcx, llbox, llboxptr_ty);
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debug2!("tuplify_box_ty = {}", ty_to_str(tcx, cbox_ty));
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// Copy expr values into boxed bindings.
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let mut bcx = bcx;
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for (i, bv) in bound_values.iter().enumerate() {
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debug2!("Copy {} into closure", bv.to_str(ccx));
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if ccx.sess.asm_comments() {
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add_comment(bcx, format!("Copy {} into closure",
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bv.to_str(ccx)));
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}
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let bound_data = GEPi(bcx, llbox, [0u, abi::box_field_body, i]);
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match bv.action {
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EnvCopy => {
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bcx = bv.datum.copy_to(bcx, INIT, bound_data);
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}
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EnvMove => {
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bcx = bv.datum.move_to(bcx, INIT, bound_data);
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}
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EnvRef => {
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Store(bcx, bv.datum.to_ref_llval(bcx), bound_data);
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}
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}
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}
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ClosureResult { llbox: llbox, cdata_ty: cdata_ty, bcx: bcx }
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}
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// Given a context and a list of upvars, build a closure. This just
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// collects the upvars and packages them up for store_environment.
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pub fn build_closure(bcx0: @mut Block,
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cap_vars: &[moves::CaptureVar],
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sigil: ast::Sigil) -> ClosureResult {
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let _icx = push_ctxt("closure::build_closure");
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// If we need to, package up the iterator body to call
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let bcx = bcx0;
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// Package up the captured upvars
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let mut env_vals = ~[];
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for cap_var in cap_vars.iter() {
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debug2!("Building closure: captured variable {:?}", *cap_var);
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let datum = expr::trans_local_var(bcx, cap_var.def);
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match cap_var.mode {
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moves::CapRef => {
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assert_eq!(sigil, ast::BorrowedSigil);
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env_vals.push(EnvValue {action: EnvRef,
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datum: datum});
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}
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moves::CapCopy => {
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env_vals.push(EnvValue {action: EnvCopy,
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datum: datum});
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}
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moves::CapMove => {
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env_vals.push(EnvValue {action: EnvMove,
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datum: datum});
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}
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}
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}
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return store_environment(bcx, env_vals, sigil);
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}
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// Given an enclosing block context, a new function context, a closure type,
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// and a list of upvars, generate code to load and populate the environment
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// with the upvars and type descriptors.
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pub fn load_environment(fcx: @mut FunctionContext,
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cdata_ty: ty::t,
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cap_vars: &[moves::CaptureVar],
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sigil: ast::Sigil) {
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let _icx = push_ctxt("closure::load_environment");
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// Don't bother to create the block if there's nothing to load
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if cap_vars.len() == 0 {
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return;
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}
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let bcx = fcx.entry_bcx.unwrap();
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// Load a pointer to the closure data, skipping over the box header:
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let llcdata = opaque_box_body(bcx, cdata_ty, fcx.llenv);
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// Store the pointer to closure data in an alloca for debug info because that's what the
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// llvm.dbg.declare intrinsic expects
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let env_pointer_alloca = if fcx.ccx.sess.opts.extra_debuginfo {
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let alloc = alloc_ty(bcx, ty::mk_mut_ptr(bcx.tcx(), cdata_ty), "__debuginfo_env_ptr");
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Store(bcx, llcdata, alloc);
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Some(alloc)
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} else {
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None
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};
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// Populate the upvars from the environment
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let mut i = 0u;
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for cap_var in cap_vars.iter() {
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let mut upvarptr = GEPi(bcx, llcdata, [0u, i]);
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match sigil {
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ast::BorrowedSigil => { upvarptr = Load(bcx, upvarptr); }
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ast::ManagedSigil | ast::OwnedSigil => {}
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}
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let def_id = ast_util::def_id_of_def(cap_var.def);
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fcx.llupvars.insert(def_id.node, upvarptr);
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for &env_pointer_alloca in env_pointer_alloca.iter() {
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debuginfo::create_captured_var_metadata(
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bcx,
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def_id.node,
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cdata_ty,
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env_pointer_alloca,
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i,
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sigil,
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cap_var.span);
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}
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i += 1u;
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}
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}
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pub fn trans_expr_fn(bcx: @mut Block,
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sigil: ast::Sigil,
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decl: &ast::fn_decl,
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body: &ast::Block,
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outer_id: ast::NodeId,
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user_id: ast::NodeId,
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dest: expr::Dest) -> @mut Block {
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/*!
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*
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* Translates the body of a closure expression.
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*
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* - `sigil`
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* - `decl`
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* - `body`
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* - `outer_id`: The id of the closure expression with the correct
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* type. This is usually the same as `user_id`, but in the
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* case of a `for` loop, the `outer_id` will have the return
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* type of boolean, and the `user_id` will have the return type
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* of `nil`.
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* - `user_id`: The id of the closure as the user expressed it.
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Generally the same as `outer_id`
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* - `cap_clause`: information about captured variables, if any.
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* - `dest`: where to write the closure value, which must be a
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(fn ptr, env) pair
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*/
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let _icx = push_ctxt("closure::trans_expr_fn");
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let dest_addr = match dest {
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expr::SaveIn(p) => p,
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expr::Ignore => {
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return bcx; // closure construction is non-side-effecting
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}
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};
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let ccx = bcx.ccx();
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let fty = node_id_type(bcx, outer_id);
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let f = match ty::get(fty).sty {
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ty::ty_closure(ref f) => f,
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_ => fail2!("expected closure")
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};
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let sub_path = vec::append_one(bcx.fcx.path.clone(),
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path_name(special_idents::anon));
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// XXX: Bad copy.
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let s = mangle_internal_name_by_path_and_seq(ccx,
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sub_path.clone(),
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"expr_fn");
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let llfn = decl_internal_rust_fn(ccx, f.sig.inputs, f.sig.output, s);
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// set an inline hint for all closures
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set_inline_hint(llfn);
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let Result {bcx: bcx, val: closure} = match sigil {
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ast::BorrowedSigil | ast::ManagedSigil | ast::OwnedSigil => {
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let cap_vars = ccx.maps.capture_map.get_copy(&user_id);
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let ClosureResult {llbox, cdata_ty, bcx}
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= build_closure(bcx, cap_vars, sigil);
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trans_closure(ccx,
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sub_path,
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decl,
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body,
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llfn,
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no_self,
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bcx.fcx.param_substs,
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user_id,
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[],
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ty::ty_fn_ret(fty),
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|fcx| load_environment(fcx, cdata_ty, cap_vars, sigil));
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rslt(bcx, llbox)
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}
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};
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fill_fn_pair(bcx, dest_addr, llfn, closure);
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return bcx;
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}
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pub fn make_closure_glue(
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cx: @mut Block,
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v: ValueRef,
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t: ty::t,
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glue_fn: &fn(@mut Block, v: ValueRef, t: ty::t) -> @mut Block) -> @mut Block {
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let _icx = push_ctxt("closure::make_closure_glue");
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let bcx = cx;
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let tcx = cx.tcx();
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let sigil = ty::ty_closure_sigil(t);
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match sigil {
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ast::BorrowedSigil => bcx,
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ast::OwnedSigil | ast::ManagedSigil => {
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let box_cell_v = GEPi(cx, v, [0u, abi::fn_field_box]);
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let box_ptr_v = Load(cx, box_cell_v);
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do with_cond(cx, IsNotNull(cx, box_ptr_v)) |bcx| {
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let closure_ty = ty::mk_opaque_closure_ptr(tcx, sigil);
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glue_fn(bcx, box_cell_v, closure_ty)
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}
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}
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}
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}
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pub fn make_opaque_cbox_drop_glue(
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bcx: @mut Block,
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sigil: ast::Sigil,
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cboxptr: ValueRef) // ptr to the opaque closure
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-> @mut Block {
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let _icx = push_ctxt("closure::make_opaque_cbox_drop_glue");
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match sigil {
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ast::BorrowedSigil => bcx,
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ast::ManagedSigil => {
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bcx.tcx().sess.bug("trying to trans drop glue of @fn")
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}
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ast::OwnedSigil => {
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glue::free_ty(
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bcx, cboxptr,
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ty::mk_opaque_closure_ptr(bcx.tcx(), sigil))
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}
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}
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}
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pub fn make_opaque_cbox_free_glue(
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bcx: @mut Block,
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sigil: ast::Sigil,
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cbox: ValueRef) // ptr to ptr to the opaque closure
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-> @mut Block {
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let _icx = push_ctxt("closure::make_opaque_cbox_free_glue");
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match sigil {
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ast::BorrowedSigil => {
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return bcx;
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}
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ast::ManagedSigil | ast::OwnedSigil => {
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/* hard cases: fallthrough to code below */
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}
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}
|
|
|
|
let ccx = bcx.ccx();
|
|
do with_cond(bcx, IsNotNull(bcx, cbox)) |bcx| {
|
|
// Load the type descr found in the cbox
|
|
let lltydescty = ccx.tydesc_type.ptr_to();
|
|
let cbox = Load(bcx, cbox);
|
|
let tydescptr = GEPi(bcx, cbox, [0u, abi::box_field_tydesc]);
|
|
let tydesc = Load(bcx, tydescptr);
|
|
let tydesc = PointerCast(bcx, tydesc, lltydescty);
|
|
|
|
// Drop the tuple data then free the descriptor
|
|
let cdata = GEPi(bcx, cbox, [0u, abi::box_field_body]);
|
|
glue::call_tydesc_glue_full(bcx, cdata, tydesc,
|
|
abi::tydesc_field_drop_glue, None);
|
|
|
|
// Free the ty descr (if necc) and the box itself
|
|
glue::trans_exchange_free(bcx, cbox);
|
|
|
|
bcx
|
|
}
|
|
}
|