914 lines
34 KiB
Rust
914 lines
34 KiB
Rust
// Copyright 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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* # Representation of Algebraic Data Types
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*
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* This module determines how to represent enums, structs, and tuples
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* based on their monomorphized types; it is responsible both for
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* choosing a representation and translating basic operations on
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* values of those types. (Note: exporting the representations for
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* debuggers is handled in debuginfo.rs, not here.)
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*
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* Note that the interface treats everything as a general case of an
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* enum, so structs/tuples/etc. have one pseudo-variant with
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* discriminant 0; i.e., as if they were a univariant enum.
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*
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* Having everything in one place will enable improvements to data
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* structure representation; possibilities include:
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*
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* - User-specified alignment (e.g., cacheline-aligning parts of
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* concurrently accessed data structures); LLVM can't represent this
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* directly, so we'd have to insert padding fields in any structure
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* that might contain one and adjust GEP indices accordingly. See
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* issue #4578.
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*
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* - Store nested enums' discriminants in the same word. Rather, if
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* some variants start with enums, and those enums representations
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* have unused alignment padding between discriminant and body, the
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* outer enum's discriminant can be stored there and those variants
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* can start at offset 0. Kind of fancy, and might need work to
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* make copies of the inner enum type cooperate, but it could help
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* with `Option` or `Result` wrapped around another enum.
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*
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* - Tagged pointers would be neat, but given that any type can be
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* used unboxed and any field can have pointers (including mutable)
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* taken to it, implementing them for Rust seems difficult.
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*/
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use std::container::Map;
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use std::libc::c_ulonglong;
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use std::option::{Option, Some, None};
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use std::num::{Bitwise};
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use lib::llvm::{ValueRef, True, IntEQ, IntNE};
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use middle::trans::_match;
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use middle::trans::build::*;
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use middle::trans::common::*;
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use middle::trans::machine;
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use middle::trans::type_::Type;
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use middle::trans::type_of;
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use middle::ty;
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use middle::ty::Disr;
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use std::vec::Vec;
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use std::vec;
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use syntax::abi::{X86, X86_64, Arm, Mips};
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use syntax::ast;
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use syntax::attr;
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use syntax::attr::IntType;
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use util::ppaux::ty_to_str;
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type Hint = attr::ReprAttr;
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/// Representations.
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pub enum Repr {
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/// C-like enums; basically an int.
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CEnum(IntType, Disr, Disr), // discriminant range (signedness based on the IntType)
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/**
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* Single-case variants, and structs/tuples/records.
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*
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* Structs with destructors need a dynamic destroyedness flag to
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* avoid running the destructor too many times; this is included
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* in the `Struct` if present.
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*/
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Univariant(Struct, bool),
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/**
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* General-case enums: for each case there is a struct, and they
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* all start with a field for the discriminant.
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*/
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General(IntType, Vec<Struct> ),
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/**
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* Two cases distinguished by a nullable pointer: the case with discriminant
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* `nndiscr` is represented by the struct `nonnull`, where the `ptrfield`th
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* field is known to be nonnull due to its type; if that field is null, then
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* it represents the other case, which is inhabited by at most one value
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* (and all other fields are undefined/unused).
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*
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* For example, `std::option::Option` instantiated at a safe pointer type
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* is represented such that `None` is a null pointer and `Some` is the
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* identity function.
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*/
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NullablePointer{ nonnull: Struct, nndiscr: Disr, ptrfield: uint,
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nullfields: Vec<ty::t> }
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}
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/// For structs, and struct-like parts of anything fancier.
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pub struct Struct {
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size: u64,
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align: u64,
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packed: bool,
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fields: Vec<ty::t> }
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/**
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* Convenience for `represent_type`. There should probably be more or
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* these, for places in trans where the `ty::t` isn't directly
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* available.
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*/
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pub fn represent_node(bcx: &Block, node: ast::NodeId) -> @Repr {
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represent_type(bcx.ccx(), node_id_type(bcx, node))
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}
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/// Decides how to represent a given type.
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pub fn represent_type(cx: &CrateContext, t: ty::t) -> @Repr {
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debug!("Representing: {}", ty_to_str(cx.tcx(), t));
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{
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let adt_reprs = cx.adt_reprs.borrow();
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match adt_reprs.get().find(&t) {
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Some(repr) => return *repr,
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None => {}
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}
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}
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let repr = @represent_type_uncached(cx, t);
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debug!("Represented as: {:?}", repr)
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let mut adt_reprs = cx.adt_reprs.borrow_mut();
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adt_reprs.get().insert(t, repr);
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return repr;
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}
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fn represent_type_uncached(cx: &CrateContext, t: ty::t) -> Repr {
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match ty::get(t).sty {
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ty::ty_tup(ref elems) => {
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return Univariant(mk_struct(cx, elems.as_slice(), false), false)
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}
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ty::ty_struct(def_id, ref substs) => {
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let fields = ty::lookup_struct_fields(cx.tcx(), def_id);
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let mut ftys = fields.map(|field| {
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ty::lookup_field_type(cx.tcx(), def_id, field.id, substs)
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});
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let packed = ty::lookup_packed(cx.tcx(), def_id);
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let dtor = ty::ty_dtor(cx.tcx(), def_id).has_drop_flag();
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if dtor { ftys.push(ty::mk_bool()); }
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return Univariant(mk_struct(cx, ftys.as_slice(), packed), dtor)
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}
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ty::ty_enum(def_id, ref substs) => {
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let cases = get_cases(cx.tcx(), def_id, substs);
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let hint = ty::lookup_repr_hint(cx.tcx(), def_id);
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if cases.len() == 0 {
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// Uninhabitable; represent as unit
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// (Typechecking will reject discriminant-sizing attrs.)
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assert_eq!(hint, attr::ReprAny);
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return Univariant(mk_struct(cx, [], false), false);
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}
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if cases.iter().all(|c| c.tys.len() == 0) {
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// All bodies empty -> intlike
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let discrs = cases.map(|c| c.discr);
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let bounds = IntBounds {
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ulo: *discrs.iter().min().unwrap(),
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uhi: *discrs.iter().max().unwrap(),
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slo: discrs.iter().map(|n| *n as i64).min().unwrap(),
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shi: discrs.iter().map(|n| *n as i64).max().unwrap()
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};
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return mk_cenum(cx, hint, &bounds);
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}
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// Since there's at least one
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// non-empty body, explicit discriminants should have
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// been rejected by a checker before this point.
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if !cases.iter().enumerate().all(|(i,c)| c.discr == (i as Disr)) {
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cx.sess().bug(format!("non-C-like enum {} with specified \
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discriminants",
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ty::item_path_str(cx.tcx(), def_id)))
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}
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if cases.len() == 1 {
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// Equivalent to a struct/tuple/newtype.
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// (Typechecking will reject discriminant-sizing attrs.)
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assert_eq!(hint, attr::ReprAny);
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return Univariant(mk_struct(cx,
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cases.get(0).tys.as_slice(),
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false),
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false)
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}
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if cases.len() == 2 && hint == attr::ReprAny {
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// Nullable pointer optimization
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let mut discr = 0;
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while discr < 2 {
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if cases.get(1 - discr).is_zerolen(cx) {
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match cases.get(discr).find_ptr() {
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Some(ptrfield) => {
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return NullablePointer {
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nndiscr: discr as u64,
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nonnull: mk_struct(cx,
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cases.get(discr)
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.tys
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.as_slice(),
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false),
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ptrfield: ptrfield,
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nullfields: cases.get(1 - discr).tys
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.clone()
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}
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}
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None => { }
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}
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}
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discr += 1;
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}
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}
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// The general case.
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assert!((cases.len() - 1) as i64 >= 0);
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let bounds = IntBounds { ulo: 0, uhi: (cases.len() - 1) as u64,
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slo: 0, shi: (cases.len() - 1) as i64 };
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let ity = range_to_inttype(cx, hint, &bounds);
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return General(ity, cases.map(|c| {
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let discr = vec!(ty_of_inttype(ity));
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mk_struct(cx,
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vec::append(discr, c.tys.as_slice()).as_slice(),
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false)
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}))
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}
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_ => cx.sess().bug("adt::represent_type called on non-ADT type")
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}
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}
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/// Determine, without doing translation, whether an ADT must be FFI-safe.
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/// For use in lint or similar, where being sound but slightly incomplete is acceptable.
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pub fn is_ffi_safe(tcx: &ty::ctxt, def_id: ast::DefId) -> bool {
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match ty::get(ty::lookup_item_type(tcx, def_id).ty).sty {
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ty::ty_enum(def_id, _) => {
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let variants = ty::enum_variants(tcx, def_id);
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// Univariant => like struct/tuple.
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if variants.len() <= 1 {
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return true;
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}
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let hint = ty::lookup_repr_hint(tcx, def_id);
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// Appropriate representation explicitly selected?
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if hint.is_ffi_safe() {
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return true;
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}
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// Option<~T> and similar are used in FFI. Rather than try to resolve type parameters
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// and recognize this case exactly, this overapproximates -- assuming that if a
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// non-C-like enum is being used in FFI then the user knows what they're doing.
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if variants.iter().any(|vi| !vi.args.is_empty()) {
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return true;
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}
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false
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}
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// struct, tuple, etc.
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// (is this right in the present of typedefs?)
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_ => true
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}
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}
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// this should probably all be in ty
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struct Case { discr: Disr, tys: Vec<ty::t> }
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impl Case {
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fn is_zerolen(&self, cx: &CrateContext) -> bool {
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mk_struct(cx, self.tys.as_slice(), false).size == 0
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}
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fn find_ptr(&self) -> Option<uint> {
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self.tys.iter().position(|&ty| mono_data_classify(ty) == MonoNonNull)
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}
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}
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fn get_cases(tcx: &ty::ctxt, def_id: ast::DefId, substs: &ty::substs) -> Vec<Case> {
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ty::enum_variants(tcx, def_id).map(|vi| {
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let arg_tys = vi.args.map(|&raw_ty| {
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ty::subst(tcx, substs, raw_ty)
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});
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Case { discr: vi.disr_val, tys: arg_tys }
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})
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}
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fn mk_struct(cx: &CrateContext, tys: &[ty::t], packed: bool) -> Struct {
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let lltys = tys.map(|&ty| type_of::sizing_type_of(cx, ty));
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let llty_rec = Type::struct_(cx, lltys, packed);
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Struct {
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size: machine::llsize_of_alloc(cx, llty_rec) /*bad*/as u64,
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align: machine::llalign_of_min(cx, llty_rec) /*bad*/as u64,
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packed: packed,
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fields: Vec::from_slice(tys),
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}
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}
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struct IntBounds {
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slo: i64,
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shi: i64,
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ulo: u64,
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uhi: u64
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}
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fn mk_cenum(cx: &CrateContext, hint: Hint, bounds: &IntBounds) -> Repr {
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let it = range_to_inttype(cx, hint, bounds);
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match it {
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attr::SignedInt(_) => CEnum(it, bounds.slo as Disr, bounds.shi as Disr),
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attr::UnsignedInt(_) => CEnum(it, bounds.ulo, bounds.uhi)
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}
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}
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fn range_to_inttype(cx: &CrateContext, hint: Hint, bounds: &IntBounds) -> IntType {
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debug!("range_to_inttype: {:?} {:?}", hint, bounds);
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// Lists of sizes to try. u64 is always allowed as a fallback.
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static choose_shortest: &'static[IntType] = &[
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attr::UnsignedInt(ast::TyU8), attr::SignedInt(ast::TyI8),
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attr::UnsignedInt(ast::TyU16), attr::SignedInt(ast::TyI16),
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attr::UnsignedInt(ast::TyU32), attr::SignedInt(ast::TyI32)];
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static at_least_32: &'static[IntType] = &[
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attr::UnsignedInt(ast::TyU32), attr::SignedInt(ast::TyI32)];
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let attempts;
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match hint {
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attr::ReprInt(span, ity) => {
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if !bounds_usable(cx, ity, bounds) {
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cx.sess().span_bug(span, "representation hint insufficient for discriminant range")
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}
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return ity;
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}
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attr::ReprExtern => {
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attempts = match cx.sess().targ_cfg.arch {
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X86 | X86_64 => at_least_32,
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// WARNING: the ARM EABI has two variants; the one corresponding to `at_least_32`
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// appears to be used on Linux and NetBSD, but some systems may use the variant
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// corresponding to `choose_shortest`. However, we don't run on those yet...?
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Arm => at_least_32,
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Mips => at_least_32,
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}
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}
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attr::ReprAny => {
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attempts = choose_shortest;
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}
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}
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for &ity in attempts.iter() {
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if bounds_usable(cx, ity, bounds) {
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return ity;
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}
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}
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return attr::UnsignedInt(ast::TyU64);
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}
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pub fn ll_inttype(cx: &CrateContext, ity: IntType) -> Type {
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match ity {
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attr::SignedInt(t) => Type::int_from_ty(cx, t),
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attr::UnsignedInt(t) => Type::uint_from_ty(cx, t)
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}
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}
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fn bounds_usable(cx: &CrateContext, ity: IntType, bounds: &IntBounds) -> bool {
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debug!("bounds_usable: {:?} {:?}", ity, bounds);
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match ity {
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attr::SignedInt(_) => {
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let lllo = C_integral(ll_inttype(cx, ity), bounds.slo as u64, true);
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let llhi = C_integral(ll_inttype(cx, ity), bounds.shi as u64, true);
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bounds.slo == const_to_int(lllo) as i64 && bounds.shi == const_to_int(llhi) as i64
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}
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attr::UnsignedInt(_) => {
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let lllo = C_integral(ll_inttype(cx, ity), bounds.ulo, false);
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let llhi = C_integral(ll_inttype(cx, ity), bounds.uhi, false);
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bounds.ulo == const_to_uint(lllo) as u64 && bounds.uhi == const_to_uint(llhi) as u64
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}
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}
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}
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pub fn ty_of_inttype(ity: IntType) -> ty::t {
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match ity {
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attr::SignedInt(t) => ty::mk_mach_int(t),
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attr::UnsignedInt(t) => ty::mk_mach_uint(t)
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}
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}
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/**
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* LLVM-level types are a little complicated.
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*
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* C-like enums need to be actual ints, not wrapped in a struct,
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* because that changes the ABI on some platforms (see issue #10308).
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*
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* For nominal types, in some cases, we need to use LLVM named structs
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* and fill in the actual contents in a second pass to prevent
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* unbounded recursion; see also the comments in `trans::type_of`.
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*/
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pub fn type_of(cx: &CrateContext, r: &Repr) -> Type {
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generic_type_of(cx, r, None, false)
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}
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pub fn sizing_type_of(cx: &CrateContext, r: &Repr) -> Type {
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generic_type_of(cx, r, None, true)
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}
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pub fn incomplete_type_of(cx: &CrateContext, r: &Repr, name: &str) -> Type {
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generic_type_of(cx, r, Some(name), false)
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}
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pub fn finish_type_of(cx: &CrateContext, r: &Repr, llty: &mut Type) {
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match *r {
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CEnum(..) | General(..) => { }
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Univariant(ref st, _) | NullablePointer{ nonnull: ref st, .. } =>
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llty.set_struct_body(struct_llfields(cx, st, false).as_slice(),
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st.packed)
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}
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}
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fn generic_type_of(cx: &CrateContext, r: &Repr, name: Option<&str>, sizing: bool) -> Type {
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match *r {
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CEnum(ity, _, _) => ll_inttype(cx, ity),
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Univariant(ref st, _) | NullablePointer{ nonnull: ref st, .. } => {
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match name {
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None => {
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Type::struct_(cx, struct_llfields(cx, st, sizing).as_slice(),
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st.packed)
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}
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Some(name) => { assert_eq!(sizing, false); Type::named_struct(cx, name) }
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}
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}
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General(ity, ref sts) => {
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// We need a representation that has:
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// * The alignment of the most-aligned field
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// * The size of the largest variant (rounded up to that alignment)
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// * No alignment padding anywhere any variant has actual data
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// (currently matters only for enums small enough to be immediate)
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// * The discriminant in an obvious place.
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//
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// So we start with the discriminant, pad it up to the alignment with
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// more of its own type, then use alignment-sized ints to get the rest
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// of the size.
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//
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// FIXME #10604: this breaks when vector types are present.
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let size = sts.iter().map(|st| st.size).max().unwrap();
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let most_aligned = sts.iter().max_by(|st| st.align).unwrap();
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let align = most_aligned.align;
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let discr_ty = ll_inttype(cx, ity);
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let discr_size = machine::llsize_of_alloc(cx, discr_ty) as u64;
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let align_units = (size + align - 1) / align - 1;
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let pad_ty = match align {
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1 => Type::array(&Type::i8(cx), align_units),
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2 => Type::array(&Type::i16(cx), align_units),
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4 => Type::array(&Type::i32(cx), align_units),
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8 if machine::llalign_of_min(cx, Type::i64(cx)) == 8 =>
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Type::array(&Type::i64(cx), align_units),
|
|
a if a.count_ones() == 1 => Type::array(&Type::vector(&Type::i32(cx), a / 4),
|
|
align_units),
|
|
_ => fail!("unsupported enum alignment: {:?}", align)
|
|
};
|
|
assert_eq!(machine::llalign_of_min(cx, pad_ty) as u64, align);
|
|
assert_eq!(align % discr_size, 0);
|
|
let fields = vec!(discr_ty,
|
|
Type::array(&discr_ty, align / discr_size - 1),
|
|
pad_ty);
|
|
match name {
|
|
None => Type::struct_(cx, fields.as_slice(), false),
|
|
Some(name) => {
|
|
let mut llty = Type::named_struct(cx, name);
|
|
llty.set_struct_body(fields.as_slice(), false);
|
|
llty
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn struct_llfields(cx: &CrateContext, st: &Struct, sizing: bool) -> Vec<Type> {
|
|
if sizing {
|
|
st.fields.map(|&ty| type_of::sizing_type_of(cx, ty))
|
|
} else {
|
|
st.fields.map(|&ty| type_of::type_of(cx, ty))
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Obtain a representation of the discriminant sufficient to translate
|
|
* destructuring; this may or may not involve the actual discriminant.
|
|
*
|
|
* This should ideally be less tightly tied to `_match`.
|
|
*/
|
|
pub fn trans_switch(bcx: &Block, r: &Repr, scrutinee: ValueRef)
|
|
-> (_match::branch_kind, Option<ValueRef>) {
|
|
match *r {
|
|
CEnum(..) | General(..) => {
|
|
(_match::switch, Some(trans_get_discr(bcx, r, scrutinee, None)))
|
|
}
|
|
NullablePointer{ nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
|
|
(_match::switch, Some(nullable_bitdiscr(bcx, nonnull, nndiscr, ptrfield, scrutinee)))
|
|
}
|
|
Univariant(..) => {
|
|
(_match::single, None)
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
/// Obtain the actual discriminant of a value.
|
|
pub fn trans_get_discr(bcx: &Block, r: &Repr, scrutinee: ValueRef, cast_to: Option<Type>)
|
|
-> ValueRef {
|
|
let signed;
|
|
let val;
|
|
match *r {
|
|
CEnum(ity, min, max) => {
|
|
val = load_discr(bcx, ity, scrutinee, min, max);
|
|
signed = ity.is_signed();
|
|
}
|
|
General(ity, ref cases) => {
|
|
let ptr = GEPi(bcx, scrutinee, [0, 0]);
|
|
val = load_discr(bcx, ity, ptr, 0, (cases.len() - 1) as Disr);
|
|
signed = ity.is_signed();
|
|
}
|
|
Univariant(..) => {
|
|
val = C_u8(bcx.ccx(), 0);
|
|
signed = false;
|
|
}
|
|
NullablePointer{ nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
|
|
val = nullable_bitdiscr(bcx, nonnull, nndiscr, ptrfield, scrutinee);
|
|
signed = false;
|
|
}
|
|
}
|
|
match cast_to {
|
|
None => val,
|
|
Some(llty) => if signed { SExt(bcx, val, llty) } else { ZExt(bcx, val, llty) }
|
|
}
|
|
}
|
|
|
|
fn nullable_bitdiscr(bcx: &Block, nonnull: &Struct, nndiscr: Disr, ptrfield: uint,
|
|
scrutinee: ValueRef) -> ValueRef {
|
|
let cmp = if nndiscr == 0 { IntEQ } else { IntNE };
|
|
let llptr = Load(bcx, GEPi(bcx, scrutinee, [0, ptrfield]));
|
|
let llptrty = type_of::type_of(bcx.ccx(), *nonnull.fields.get(ptrfield));
|
|
ICmp(bcx, cmp, llptr, C_null(llptrty))
|
|
}
|
|
|
|
/// Helper for cases where the discriminant is simply loaded.
|
|
fn load_discr(bcx: &Block, ity: IntType, ptr: ValueRef, min: Disr, max: Disr)
|
|
-> ValueRef {
|
|
let llty = ll_inttype(bcx.ccx(), ity);
|
|
assert_eq!(val_ty(ptr), llty.ptr_to());
|
|
let bits = machine::llbitsize_of_real(bcx.ccx(), llty);
|
|
assert!(bits <= 64);
|
|
let mask = (-1u64 >> (64 - bits)) as Disr;
|
|
if (max + 1) & mask == min & mask {
|
|
// i.e., if the range is everything. The lo==hi case would be
|
|
// rejected by the LLVM verifier (it would mean either an
|
|
// empty set, which is impossible, or the entire range of the
|
|
// type, which is pointless).
|
|
Load(bcx, ptr)
|
|
} else {
|
|
// llvm::ConstantRange can deal with ranges that wrap around,
|
|
// so an overflow on (max + 1) is fine.
|
|
LoadRangeAssert(bcx, ptr, min as c_ulonglong,
|
|
(max + 1) as c_ulonglong,
|
|
/* signed: */ True)
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Yield information about how to dispatch a case of the
|
|
* discriminant-like value returned by `trans_switch`.
|
|
*
|
|
* This should ideally be less tightly tied to `_match`.
|
|
*/
|
|
pub fn trans_case<'a>(bcx: &'a Block<'a>, r: &Repr, discr: Disr)
|
|
-> _match::opt_result<'a> {
|
|
match *r {
|
|
CEnum(ity, _, _) => {
|
|
_match::single_result(rslt(bcx, C_integral(ll_inttype(bcx.ccx(), ity),
|
|
discr as u64, true)))
|
|
}
|
|
General(ity, _) => {
|
|
_match::single_result(rslt(bcx, C_integral(ll_inttype(bcx.ccx(), ity),
|
|
discr as u64, true)))
|
|
}
|
|
Univariant(..) => {
|
|
bcx.ccx().sess().bug("no cases for univariants or structs")
|
|
}
|
|
NullablePointer{ .. } => {
|
|
assert!(discr == 0 || discr == 1);
|
|
_match::single_result(rslt(bcx, C_i1(bcx.ccx(), discr != 0)))
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Begin initializing a new value of the given case of the given
|
|
* representation. The fields, if any, should then be initialized via
|
|
* `trans_field_ptr`.
|
|
*/
|
|
pub fn trans_start_init(bcx: &Block, r: &Repr, val: ValueRef, discr: Disr) {
|
|
match *r {
|
|
CEnum(ity, min, max) => {
|
|
assert_discr_in_range(ity, min, max, discr);
|
|
Store(bcx, C_integral(ll_inttype(bcx.ccx(), ity), discr as u64, true),
|
|
val)
|
|
}
|
|
General(ity, _) => {
|
|
Store(bcx, C_integral(ll_inttype(bcx.ccx(), ity), discr as u64, true),
|
|
GEPi(bcx, val, [0, 0]))
|
|
}
|
|
Univariant(ref st, true) => {
|
|
assert_eq!(discr, 0);
|
|
Store(bcx, C_bool(bcx.ccx(), true),
|
|
GEPi(bcx, val, [0, st.fields.len() - 1]))
|
|
}
|
|
Univariant(..) => {
|
|
assert_eq!(discr, 0);
|
|
}
|
|
NullablePointer{ nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
|
|
if discr != nndiscr {
|
|
let llptrptr = GEPi(bcx, val, [0, ptrfield]);
|
|
let llptrty = type_of::type_of(bcx.ccx(),
|
|
*nonnull.fields.get(ptrfield));
|
|
Store(bcx, C_null(llptrty), llptrptr)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn assert_discr_in_range(ity: IntType, min: Disr, max: Disr, discr: Disr) {
|
|
match ity {
|
|
attr::UnsignedInt(_) => assert!(min <= discr && discr <= max),
|
|
attr::SignedInt(_) => assert!(min as i64 <= discr as i64 && discr as i64 <= max as i64)
|
|
}
|
|
}
|
|
|
|
/**
|
|
* The number of fields in a given case; for use when obtaining this
|
|
* information from the type or definition is less convenient.
|
|
*/
|
|
pub fn num_args(r: &Repr, discr: Disr) -> uint {
|
|
match *r {
|
|
CEnum(..) => 0,
|
|
Univariant(ref st, dtor) => {
|
|
assert_eq!(discr, 0);
|
|
st.fields.len() - (if dtor { 1 } else { 0 })
|
|
}
|
|
General(_, ref cases) => cases.get(discr as uint).fields.len() - 1,
|
|
NullablePointer{ nonnull: ref nonnull, nndiscr,
|
|
nullfields: ref nullfields, .. } => {
|
|
if discr == nndiscr { nonnull.fields.len() } else { nullfields.len() }
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Access a field, at a point when the value's case is known.
|
|
pub fn deref_ty(ccx: &CrateContext, r: &Repr) -> ty::t {
|
|
match *r {
|
|
CEnum(..) => {
|
|
ccx.sess().bug("deref of c-like enum")
|
|
}
|
|
Univariant(ref st, _) => {
|
|
*st.fields.get(0)
|
|
}
|
|
General(_, ref cases) => {
|
|
assert!(cases.len() == 1);
|
|
*cases.get(0).fields.get(0)
|
|
}
|
|
NullablePointer{ .. } => {
|
|
ccx.sess().bug("deref of nullable ptr")
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Access a field, at a point when the value's case is known.
|
|
pub fn trans_field_ptr(bcx: &Block, r: &Repr, val: ValueRef, discr: Disr,
|
|
ix: uint) -> ValueRef {
|
|
// Note: if this ever needs to generate conditionals (e.g., if we
|
|
// decide to do some kind of cdr-coding-like non-unique repr
|
|
// someday), it will need to return a possibly-new bcx as well.
|
|
match *r {
|
|
CEnum(..) => {
|
|
bcx.ccx().sess().bug("element access in C-like enum")
|
|
}
|
|
Univariant(ref st, _dtor) => {
|
|
assert_eq!(discr, 0);
|
|
struct_field_ptr(bcx, st, val, ix, false)
|
|
}
|
|
General(_, ref cases) => {
|
|
struct_field_ptr(bcx, cases.get(discr as uint), val, ix + 1, true)
|
|
}
|
|
NullablePointer{ nonnull: ref nonnull, nullfields: ref nullfields,
|
|
nndiscr, .. } => {
|
|
if discr == nndiscr {
|
|
struct_field_ptr(bcx, nonnull, val, ix, false)
|
|
} else {
|
|
// The unit-like case might have a nonzero number of unit-like fields.
|
|
// (e.g., Result or Either with () as one side.)
|
|
let ty = type_of::type_of(bcx.ccx(), *nullfields.get(ix));
|
|
assert_eq!(machine::llsize_of_alloc(bcx.ccx(), ty), 0);
|
|
// The contents of memory at this pointer can't matter, but use
|
|
// the value that's "reasonable" in case of pointer comparison.
|
|
PointerCast(bcx, val, ty.ptr_to())
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn struct_field_ptr(bcx: &Block, st: &Struct, val: ValueRef, ix: uint,
|
|
needs_cast: bool) -> ValueRef {
|
|
let ccx = bcx.ccx();
|
|
|
|
let val = if needs_cast {
|
|
let fields = st.fields.map(|&ty| type_of::type_of(ccx, ty));
|
|
let real_ty = Type::struct_(ccx, fields.as_slice(), st.packed);
|
|
PointerCast(bcx, val, real_ty.ptr_to())
|
|
} else {
|
|
val
|
|
};
|
|
|
|
GEPi(bcx, val, [0, ix])
|
|
}
|
|
|
|
/// Access the struct drop flag, if present.
|
|
pub fn trans_drop_flag_ptr(bcx: &Block, r: &Repr, val: ValueRef) -> ValueRef {
|
|
match *r {
|
|
Univariant(ref st, true) => GEPi(bcx, val, [0, st.fields.len() - 1]),
|
|
_ => bcx.ccx().sess().bug("tried to get drop flag of non-droppable type")
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Construct a constant value, suitable for initializing a
|
|
* GlobalVariable, given a case and constant values for its fields.
|
|
* Note that this may have a different LLVM type (and different
|
|
* alignment!) from the representation's `type_of`, so it needs a
|
|
* pointer cast before use.
|
|
*
|
|
* The LLVM type system does not directly support unions, and only
|
|
* pointers can be bitcast, so a constant (and, by extension, the
|
|
* GlobalVariable initialized by it) will have a type that can vary
|
|
* depending on which case of an enum it is.
|
|
*
|
|
* To understand the alignment situation, consider `enum E { V64(u64),
|
|
* V32(u32, u32) }` on win32. The type has 8-byte alignment to
|
|
* accommodate the u64, but `V32(x, y)` would have LLVM type `{i32,
|
|
* i32, i32}`, which is 4-byte aligned.
|
|
*
|
|
* Currently the returned value has the same size as the type, but
|
|
* this could be changed in the future to avoid allocating unnecessary
|
|
* space after values of shorter-than-maximum cases.
|
|
*/
|
|
pub fn trans_const(ccx: &CrateContext, r: &Repr, discr: Disr,
|
|
vals: &[ValueRef]) -> ValueRef {
|
|
match *r {
|
|
CEnum(ity, min, max) => {
|
|
assert_eq!(vals.len(), 0);
|
|
assert_discr_in_range(ity, min, max, discr);
|
|
C_integral(ll_inttype(ccx, ity), discr as u64, true)
|
|
}
|
|
General(ity, ref cases) => {
|
|
let case = cases.get(discr as uint);
|
|
let max_sz = cases.iter().map(|x| x.size).max().unwrap();
|
|
let lldiscr = C_integral(ll_inttype(ccx, ity), discr as u64, true);
|
|
let contents = build_const_struct(ccx,
|
|
case,
|
|
vec::append(
|
|
vec!(lldiscr),
|
|
vals).as_slice());
|
|
C_struct(ccx, vec::append(
|
|
contents,
|
|
&[padding(ccx, max_sz - case.size)]).as_slice(),
|
|
false)
|
|
}
|
|
Univariant(ref st, _dro) => {
|
|
assert!(discr == 0);
|
|
let contents = build_const_struct(ccx, st, vals);
|
|
C_struct(ccx, contents.as_slice(), st.packed)
|
|
}
|
|
NullablePointer{ nonnull: ref nonnull, nndiscr, .. } => {
|
|
if discr == nndiscr {
|
|
C_struct(ccx, build_const_struct(ccx,
|
|
nonnull,
|
|
vals).as_slice(),
|
|
false)
|
|
} else {
|
|
let vals = nonnull.fields.map(|&ty| {
|
|
// Always use null even if it's not the `ptrfield`th
|
|
// field; see #8506.
|
|
C_null(type_of::sizing_type_of(ccx, ty))
|
|
}).move_iter().collect::<Vec<ValueRef> >();
|
|
C_struct(ccx, build_const_struct(ccx,
|
|
nonnull,
|
|
vals.as_slice()).as_slice(),
|
|
false)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Building structs is a little complicated, because we might need to
|
|
* insert padding if a field's value is less aligned than its type.
|
|
*
|
|
* Continuing the example from `trans_const`, a value of type `(u32,
|
|
* E)` should have the `E` at offset 8, but if that field's
|
|
* initializer is 4-byte aligned then simply translating the tuple as
|
|
* a two-element struct will locate it at offset 4, and accesses to it
|
|
* will read the wrong memory.
|
|
*/
|
|
fn build_const_struct(ccx: &CrateContext, st: &Struct, vals: &[ValueRef])
|
|
-> Vec<ValueRef> {
|
|
assert_eq!(vals.len(), st.fields.len());
|
|
|
|
let mut offset = 0;
|
|
let mut cfields = Vec::new();
|
|
for (i, &ty) in st.fields.iter().enumerate() {
|
|
let llty = type_of::sizing_type_of(ccx, ty);
|
|
let type_align = machine::llalign_of_min(ccx, llty)
|
|
/*bad*/as u64;
|
|
let val_align = machine::llalign_of_min(ccx, val_ty(vals[i]))
|
|
/*bad*/as u64;
|
|
let target_offset = roundup(offset, type_align);
|
|
offset = roundup(offset, val_align);
|
|
if offset != target_offset {
|
|
cfields.push(padding(ccx, target_offset - offset));
|
|
offset = target_offset;
|
|
}
|
|
assert!(!is_undef(vals[i]));
|
|
cfields.push(vals[i]);
|
|
offset += machine::llsize_of_alloc(ccx, llty) as u64
|
|
}
|
|
|
|
return cfields;
|
|
}
|
|
|
|
fn padding(ccx: &CrateContext, size: u64) -> ValueRef {
|
|
C_undef(Type::array(&Type::i8(ccx), size))
|
|
}
|
|
|
|
// FIXME this utility routine should be somewhere more general
|
|
#[inline]
|
|
fn roundup(x: u64, a: u64) -> u64 { ((x + (a - 1)) / a) * a }
|
|
|
|
/// Get the discriminant of a constant value. (Not currently used.)
|
|
pub fn const_get_discrim(ccx: &CrateContext, r: &Repr, val: ValueRef)
|
|
-> Disr {
|
|
match *r {
|
|
CEnum(ity, _, _) => {
|
|
match ity {
|
|
attr::SignedInt(..) => const_to_int(val) as Disr,
|
|
attr::UnsignedInt(..) => const_to_uint(val) as Disr
|
|
}
|
|
}
|
|
General(ity, _) => {
|
|
match ity {
|
|
attr::SignedInt(..) => const_to_int(const_get_elt(ccx, val, [0])) as Disr,
|
|
attr::UnsignedInt(..) => const_to_uint(const_get_elt(ccx, val, [0])) as Disr
|
|
}
|
|
}
|
|
Univariant(..) => 0,
|
|
NullablePointer{ nndiscr, ptrfield, .. } => {
|
|
if is_null(const_struct_field(ccx, val, ptrfield)) {
|
|
/* subtraction as uint is ok because nndiscr is either 0 or 1 */
|
|
(1 - nndiscr) as Disr
|
|
} else {
|
|
nndiscr
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Extract a field of a constant value, as appropriate for its
|
|
* representation.
|
|
*
|
|
* (Not to be confused with `common::const_get_elt`, which operates on
|
|
* raw LLVM-level structs and arrays.)
|
|
*/
|
|
pub fn const_get_field(ccx: &CrateContext, r: &Repr, val: ValueRef,
|
|
_discr: Disr, ix: uint) -> ValueRef {
|
|
match *r {
|
|
CEnum(..) => ccx.sess().bug("element access in C-like enum const"),
|
|
Univariant(..) => const_struct_field(ccx, val, ix),
|
|
General(..) => const_struct_field(ccx, val, ix + 1),
|
|
NullablePointer{ .. } => const_struct_field(ccx, val, ix)
|
|
}
|
|
}
|
|
|
|
/// Extract field of struct-like const, skipping our alignment padding.
|
|
fn const_struct_field(ccx: &CrateContext, val: ValueRef, ix: uint)
|
|
-> ValueRef {
|
|
// Get the ix-th non-undef element of the struct.
|
|
let mut real_ix = 0; // actual position in the struct
|
|
let mut ix = ix; // logical index relative to real_ix
|
|
let mut field;
|
|
loop {
|
|
loop {
|
|
field = const_get_elt(ccx, val, [real_ix]);
|
|
if !is_undef(field) {
|
|
break;
|
|
}
|
|
real_ix = real_ix + 1;
|
|
}
|
|
if ix == 0 {
|
|
return field;
|
|
}
|
|
ix = ix - 1;
|
|
real_ix = real_ix + 1;
|
|
}
|
|
}
|
|
|
|
/// Is it safe to bitcast a value to the one field of its one variant?
|
|
pub fn is_newtypeish(r: &Repr) -> bool {
|
|
match *r {
|
|
Univariant(ref st, false) => st.fields.len() == 1,
|
|
_ => false
|
|
}
|
|
}
|