1341 lines
52 KiB
Rust
1341 lines
52 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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//! # 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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pub use self::Repr::*;
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use super::Disr;
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use std;
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use std::rc::Rc;
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use llvm::{ValueRef, True, IntEQ, IntNE};
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use rustc::ty::subst::Substs;
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use rustc::ty::{self, Ty, TyCtxt};
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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 abi::FAT_PTR_ADDR;
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use build::*;
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use common::*;
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use debuginfo::DebugLoc;
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use glue;
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use machine;
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use monomorphize;
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use type_::Type;
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use type_of;
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use value::Value;
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#[derive(Copy, Clone, PartialEq)]
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pub enum BranchKind {
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Switch,
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Single
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}
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type Hint = attr::ReprAttr;
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/// Representations.
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#[derive(Eq, PartialEq, Debug)]
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pub enum Repr<'tcx> {
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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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/// Single-case variants, and structs/tuples/records.
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Univariant(Struct<'tcx>),
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/// Untagged unions.
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UntaggedUnion(Union<'tcx>),
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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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General(IntType, Vec<Struct<'tcx>>),
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/// Two cases distinguished by a nullable pointer: the case with discriminant
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/// `nndiscr` must have single field which is known to be nonnull due to its type.
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/// The other case is known to be zero sized. Hence we represent the enum
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/// as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
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/// otherwise it indicates the other case.
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RawNullablePointer {
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nndiscr: Disr,
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nnty: Ty<'tcx>,
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nullfields: Vec<Ty<'tcx>>
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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 `discrfield`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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StructWrappedNullablePointer {
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nonnull: Struct<'tcx>,
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nndiscr: Disr,
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discrfield: DiscrField,
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nullfields: Vec<Ty<'tcx>>,
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}
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}
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/// For structs, and struct-like parts of anything fancier.
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#[derive(Eq, PartialEq, Debug)]
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pub struct Struct<'tcx> {
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// If the struct is DST, then the size and alignment do not take into
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// account the unsized fields of the struct.
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pub size: u64,
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pub align: u32,
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pub sized: bool,
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pub packed: bool,
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pub fields: Vec<Ty<'tcx>>,
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}
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/// For untagged unions.
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#[derive(Eq, PartialEq, Debug)]
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pub struct Union<'tcx> {
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pub min_size: u64,
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pub align: u32,
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pub packed: bool,
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pub fields: Vec<Ty<'tcx>>,
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}
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#[derive(Copy, Clone)]
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pub struct MaybeSizedValue {
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pub value: ValueRef,
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pub meta: ValueRef,
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}
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impl MaybeSizedValue {
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pub fn sized(value: ValueRef) -> MaybeSizedValue {
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MaybeSizedValue {
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value: value,
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meta: std::ptr::null_mut()
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}
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}
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pub fn unsized_(value: ValueRef, meta: ValueRef) -> MaybeSizedValue {
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MaybeSizedValue {
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value: value,
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meta: meta
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}
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}
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pub fn has_meta(&self) -> bool {
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!self.meta.is_null()
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}
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}
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/// Decides how to represent a given type.
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pub fn represent_type<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
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t: Ty<'tcx>)
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-> Rc<Repr<'tcx>> {
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debug!("Representing: {}", t);
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if let Some(repr) = cx.adt_reprs().borrow().get(&t) {
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return repr.clone();
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}
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let repr = Rc::new(represent_type_uncached(cx, t));
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debug!("Represented as: {:?}", repr);
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cx.adt_reprs().borrow_mut().insert(t, repr.clone());
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repr
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}
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fn represent_type_uncached<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
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t: Ty<'tcx>) -> Repr<'tcx> {
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match t.sty {
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ty::TyTuple(ref elems) => {
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Univariant(mk_struct(cx, &elems[..], false, t))
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}
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ty::TyStruct(def, substs) => {
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let ftys = def.struct_variant().fields.iter().map(|field| {
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monomorphize::field_ty(cx.tcx(), substs, field)
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}).collect::<Vec<_>>();
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let packed = cx.tcx().lookup_packed(def.did);
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Univariant(mk_struct(cx, &ftys[..], packed, t))
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}
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ty::TyUnion(def, substs) => {
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let ftys = def.struct_variant().fields.iter().map(|field| {
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monomorphize::field_ty(cx.tcx(), substs, field)
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}).collect::<Vec<_>>();
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let packed = cx.tcx().lookup_packed(def.did);
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UntaggedUnion(mk_union(cx, &ftys[..], packed, t))
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}
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ty::TyClosure(_, ref substs) => {
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Univariant(mk_struct(cx, &substs.upvar_tys, false, t))
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}
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ty::TyEnum(def, substs) => {
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let cases = get_cases(cx.tcx(), def, substs);
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let hint = *cx.tcx().lookup_repr_hints(def.did).get(0)
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.unwrap_or(&attr::ReprAny);
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if cases.is_empty() {
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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, t));
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}
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if cases.iter().all(|c| c.tys.is_empty()) {
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// All bodies empty -> intlike
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let discrs: Vec<_> = cases.iter().map(|c| Disr::from(c.discr)).collect();
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let bounds = IntBounds {
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ulo: discrs.iter().min().unwrap().0,
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uhi: discrs.iter().max().unwrap().0,
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slo: discrs.iter().map(|n| n.0 as i64).min().unwrap(),
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shi: discrs.iter().map(|n| n.0 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 == Disr::from(i)) {
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bug!("non-C-like enum {} with specified discriminants",
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cx.tcx().item_path_str(def.did));
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}
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if cases.len() == 1 && hint == attr::ReprAny {
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// Equivalent to a struct/tuple/newtype.
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return Univariant(mk_struct(cx, &cases[0].tys, false, t));
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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[1 - discr].is_zerolen(cx, t) {
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let st = mk_struct(cx, &cases[discr].tys,
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false, t);
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match cases[discr].find_ptr(cx) {
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Some(ref df) if df.len() == 1 && st.fields.len() == 1 => {
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return RawNullablePointer {
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nndiscr: Disr::from(discr),
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nnty: st.fields[0],
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nullfields: cases[1 - discr].tys.clone()
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};
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}
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Some(mut discrfield) => {
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discrfield.push(0);
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discrfield.reverse();
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return StructWrappedNullablePointer {
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nndiscr: Disr::from(discr),
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nonnull: st,
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discrfield: discrfield,
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nullfields: cases[1 - discr].tys.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 min_ity = range_to_inttype(cx, hint, &bounds);
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// Create the set of structs that represent each variant
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// Use the minimum integer type we figured out above
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let fields : Vec<_> = cases.iter().map(|c| {
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let mut ftys = vec!(ty_of_inttype(cx.tcx(), min_ity));
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ftys.extend_from_slice(&c.tys);
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mk_struct(cx, &ftys, false, t)
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}).collect();
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// Check to see if we should use a different type for the
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// discriminant. If the overall alignment of the type is
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// the same as the first field in each variant, we can safely use
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// an alignment-sized type.
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// We increase the size of the discriminant to avoid LLVM copying
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// padding when it doesn't need to. This normally causes unaligned
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// load/stores and excessive memcpy/memset operations. By using a
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// bigger integer size, LLVM can be sure about it's contents and
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// won't be so conservative.
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// This check is needed to avoid increasing the size of types when
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// the alignment of the first field is smaller than the overall
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// alignment of the type.
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let (_, align) = union_size_and_align(&fields);
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let mut use_align = true;
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for st in &fields {
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// Get the first non-zero-sized field
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let field = st.fields.iter().skip(1).filter(|ty| {
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let t = type_of::sizing_type_of(cx, **ty);
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machine::llsize_of_real(cx, t) != 0 ||
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// This case is only relevant for zero-sized types with large alignment
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machine::llalign_of_min(cx, t) != 1
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}).next();
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if let Some(field) = field {
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let field_align = type_of::align_of(cx, *field);
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if field_align != align {
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use_align = false;
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break;
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}
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}
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}
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// If the alignment is smaller than the chosen discriminant size, don't use the
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// alignment as the final size.
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let min_ty = ll_inttype(&cx, min_ity);
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let min_size = machine::llsize_of_real(cx, min_ty);
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if (align as u64) < min_size {
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use_align = false;
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}
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let ity = if use_align {
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// Use the overall alignment
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match align {
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1 => attr::UnsignedInt(ast::UintTy::U8),
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2 => attr::UnsignedInt(ast::UintTy::U16),
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4 => attr::UnsignedInt(ast::UintTy::U32),
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8 if machine::llalign_of_min(cx, Type::i64(cx)) == 8 =>
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attr::UnsignedInt(ast::UintTy::U64),
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_ => min_ity // use min_ity as a fallback
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}
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} else {
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min_ity
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};
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let fields : Vec<_> = cases.iter().map(|c| {
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let mut ftys = vec!(ty_of_inttype(cx.tcx(), ity));
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ftys.extend_from_slice(&c.tys);
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mk_struct(cx, &ftys[..], false, t)
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}).collect();
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ensure_enum_fits_in_address_space(cx, &fields[..], t);
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General(ity, fields)
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}
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_ => bug!("adt::represent_type called on non-ADT type: {}", t)
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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<'tcx> {
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discr: Disr,
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tys: Vec<Ty<'tcx>>
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}
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/// This represents the (GEP) indices to follow to get to the discriminant field
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pub type DiscrField = Vec<usize>;
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fn find_discr_field_candidate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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ty: Ty<'tcx>,
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mut path: DiscrField)
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-> Option<DiscrField> {
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match ty.sty {
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// Fat &T/&mut T/Box<T> i.e. T is [T], str, or Trait
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ty::TyRef(_, ty::TypeAndMut { ty, .. }) | ty::TyBox(ty) if !type_is_sized(tcx, ty) => {
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path.push(FAT_PTR_ADDR);
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Some(path)
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},
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// Regular thin pointer: &T/&mut T/Box<T>
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ty::TyRef(..) | ty::TyBox(..) => Some(path),
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// Function pointer: `fn() -> i32`
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ty::TyFnPtr(_) => Some(path),
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// Is this the NonZero lang item wrapping a pointer or integer type?
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ty::TyStruct(def, substs) if Some(def.did) == tcx.lang_items.non_zero() => {
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let nonzero_fields = &def.struct_variant().fields;
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assert_eq!(nonzero_fields.len(), 1);
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let field_ty = monomorphize::field_ty(tcx, substs, &nonzero_fields[0]);
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match field_ty.sty {
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ty::TyRawPtr(ty::TypeAndMut { ty, .. }) if !type_is_sized(tcx, ty) => {
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path.extend_from_slice(&[0, FAT_PTR_ADDR]);
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Some(path)
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},
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ty::TyRawPtr(..) | ty::TyInt(..) | ty::TyUint(..) => {
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path.push(0);
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Some(path)
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},
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_ => None
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}
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},
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// Perhaps one of the fields of this struct is non-zero
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// let's recurse and find out
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ty::TyStruct(def, substs) => {
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for (j, field) in def.struct_variant().fields.iter().enumerate() {
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let field_ty = monomorphize::field_ty(tcx, substs, field);
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if let Some(mut fpath) = find_discr_field_candidate(tcx, field_ty, path.clone()) {
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fpath.push(j);
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return Some(fpath);
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}
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}
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None
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},
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// Perhaps one of the upvars of this struct is non-zero
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// Let's recurse and find out!
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ty::TyClosure(_, ref substs) => {
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for (j, &ty) in substs.upvar_tys.iter().enumerate() {
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if let Some(mut fpath) = find_discr_field_candidate(tcx, ty, path.clone()) {
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fpath.push(j);
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return Some(fpath);
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}
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}
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None
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},
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// Can we use one of the fields in this tuple?
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ty::TyTuple(ref tys) => {
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for (j, &ty) in tys.iter().enumerate() {
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if let Some(mut fpath) = find_discr_field_candidate(tcx, ty, path.clone()) {
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fpath.push(j);
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return Some(fpath);
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}
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}
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None
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},
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// Is this a fixed-size array of something non-zero
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// with at least one element?
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ty::TyArray(ety, d) if d > 0 => {
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if let Some(mut vpath) = find_discr_field_candidate(tcx, ety, path) {
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vpath.push(0);
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Some(vpath)
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} else {
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None
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}
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},
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// Anything else is not a pointer
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_ => None
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}
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}
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impl<'tcx> Case<'tcx> {
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fn is_zerolen<'a>(&self, cx: &CrateContext<'a, 'tcx>, scapegoat: Ty<'tcx>) -> bool {
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mk_struct(cx, &self.tys, false, scapegoat).size == 0
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}
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fn find_ptr<'a>(&self, cx: &CrateContext<'a, 'tcx>) -> Option<DiscrField> {
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for (i, &ty) in self.tys.iter().enumerate() {
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if let Some(mut path) = find_discr_field_candidate(cx.tcx(), ty, vec![]) {
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path.push(i);
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return Some(path);
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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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fn get_cases<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
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adt: ty::AdtDef<'tcx>,
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substs: &Substs<'tcx>)
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-> Vec<Case<'tcx>> {
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adt.variants.iter().map(|vi| {
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let field_tys = vi.fields.iter().map(|field| {
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monomorphize::field_ty(tcx, substs, field)
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}).collect();
|
|
Case { discr: Disr::from(vi.disr_val), tys: field_tys }
|
|
}).collect()
|
|
}
|
|
|
|
fn mk_struct<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
tys: &[Ty<'tcx>], packed: bool,
|
|
scapegoat: Ty<'tcx>)
|
|
-> Struct<'tcx> {
|
|
let sized = tys.iter().all(|&ty| type_is_sized(cx.tcx(), ty));
|
|
let lltys : Vec<Type> = if sized {
|
|
tys.iter().map(|&ty| type_of::sizing_type_of(cx, ty)).collect()
|
|
} else {
|
|
tys.iter().filter(|&ty| type_is_sized(cx.tcx(), *ty))
|
|
.map(|&ty| type_of::sizing_type_of(cx, ty)).collect()
|
|
};
|
|
|
|
ensure_struct_fits_in_address_space(cx, &lltys[..], packed, scapegoat);
|
|
|
|
let llty_rec = Type::struct_(cx, &lltys[..], packed);
|
|
Struct {
|
|
size: machine::llsize_of_alloc(cx, llty_rec),
|
|
align: machine::llalign_of_min(cx, llty_rec),
|
|
sized: sized,
|
|
packed: packed,
|
|
fields: tys.to_vec(),
|
|
}
|
|
}
|
|
|
|
fn mk_union<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
tys: &[Ty<'tcx>], packed: bool,
|
|
_scapegoat: Ty<'tcx>)
|
|
-> Union<'tcx> {
|
|
let mut min_size = 0;
|
|
let mut align = 0;
|
|
for llty in tys.iter().map(|&ty| type_of::sizing_type_of(cx, ty)) {
|
|
let field_size = machine::llsize_of_alloc(cx, llty);
|
|
if min_size < field_size {
|
|
min_size = field_size;
|
|
}
|
|
let field_align = machine::llalign_of_min(cx, llty);
|
|
if align < field_align {
|
|
align = field_align;
|
|
}
|
|
}
|
|
|
|
Union {
|
|
min_size: min_size,
|
|
align: if packed { 1 } else { align },
|
|
packed: packed,
|
|
fields: tys.to_vec(),
|
|
}
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
struct IntBounds {
|
|
slo: i64,
|
|
shi: i64,
|
|
ulo: u64,
|
|
uhi: u64
|
|
}
|
|
|
|
fn mk_cenum<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
hint: Hint, bounds: &IntBounds)
|
|
-> Repr<'tcx> {
|
|
let it = range_to_inttype(cx, hint, bounds);
|
|
match it {
|
|
attr::SignedInt(_) => CEnum(it, Disr(bounds.slo as u64), Disr(bounds.shi as u64)),
|
|
attr::UnsignedInt(_) => CEnum(it, Disr(bounds.ulo), Disr(bounds.uhi))
|
|
}
|
|
}
|
|
|
|
fn range_to_inttype(cx: &CrateContext, hint: Hint, bounds: &IntBounds) -> IntType {
|
|
debug!("range_to_inttype: {:?} {:?}", hint, bounds);
|
|
// Lists of sizes to try. u64 is always allowed as a fallback.
|
|
#[allow(non_upper_case_globals)]
|
|
const choose_shortest: &'static [IntType] = &[
|
|
attr::UnsignedInt(ast::UintTy::U8), attr::SignedInt(ast::IntTy::I8),
|
|
attr::UnsignedInt(ast::UintTy::U16), attr::SignedInt(ast::IntTy::I16),
|
|
attr::UnsignedInt(ast::UintTy::U32), attr::SignedInt(ast::IntTy::I32)];
|
|
#[allow(non_upper_case_globals)]
|
|
const at_least_32: &'static [IntType] = &[
|
|
attr::UnsignedInt(ast::UintTy::U32), attr::SignedInt(ast::IntTy::I32)];
|
|
|
|
let attempts;
|
|
match hint {
|
|
attr::ReprInt(span, ity) => {
|
|
if !bounds_usable(cx, ity, bounds) {
|
|
span_bug!(span, "representation hint insufficient for discriminant range")
|
|
}
|
|
return ity;
|
|
}
|
|
attr::ReprExtern => {
|
|
attempts = match &cx.sess().target.target.arch[..] {
|
|
// WARNING: the ARM EABI has two variants; the one corresponding to `at_least_32`
|
|
// appears to be used on Linux and NetBSD, but some systems may use the variant
|
|
// corresponding to `choose_shortest`. However, we don't run on those yet...?
|
|
"arm" => at_least_32,
|
|
_ => at_least_32,
|
|
}
|
|
}
|
|
attr::ReprAny => {
|
|
attempts = choose_shortest;
|
|
},
|
|
attr::ReprPacked => {
|
|
bug!("range_to_inttype: found ReprPacked on an enum");
|
|
}
|
|
attr::ReprSimd => {
|
|
bug!("range_to_inttype: found ReprSimd on an enum");
|
|
}
|
|
}
|
|
for &ity in attempts {
|
|
if bounds_usable(cx, ity, bounds) {
|
|
return ity;
|
|
}
|
|
}
|
|
return attr::UnsignedInt(ast::UintTy::U64);
|
|
}
|
|
|
|
pub fn ll_inttype(cx: &CrateContext, ity: IntType) -> Type {
|
|
match ity {
|
|
attr::SignedInt(t) => Type::int_from_ty(cx, t),
|
|
attr::UnsignedInt(t) => Type::uint_from_ty(cx, t)
|
|
}
|
|
}
|
|
|
|
fn bounds_usable(cx: &CrateContext, ity: IntType, bounds: &IntBounds) -> bool {
|
|
debug!("bounds_usable: {:?} {:?}", ity, bounds);
|
|
match ity {
|
|
attr::SignedInt(_) => {
|
|
let lllo = C_integral(ll_inttype(cx, ity), bounds.slo as u64, true);
|
|
let llhi = C_integral(ll_inttype(cx, ity), bounds.shi as u64, true);
|
|
bounds.slo == const_to_int(lllo) as i64 && bounds.shi == const_to_int(llhi) as i64
|
|
}
|
|
attr::UnsignedInt(_) => {
|
|
let lllo = C_integral(ll_inttype(cx, ity), bounds.ulo, false);
|
|
let llhi = C_integral(ll_inttype(cx, ity), bounds.uhi, false);
|
|
bounds.ulo == const_to_uint(lllo) as u64 && bounds.uhi == const_to_uint(llhi) as u64
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn ty_of_inttype<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ity: IntType) -> Ty<'tcx> {
|
|
match ity {
|
|
attr::SignedInt(t) => tcx.mk_mach_int(t),
|
|
attr::UnsignedInt(t) => tcx.mk_mach_uint(t)
|
|
}
|
|
}
|
|
|
|
// LLVM doesn't like types that don't fit in the address space
|
|
fn ensure_struct_fits_in_address_space<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
|
|
fields: &[Type],
|
|
packed: bool,
|
|
scapegoat: Ty<'tcx>) {
|
|
let mut offset = 0;
|
|
for &llty in fields {
|
|
// Invariant: offset < ccx.obj_size_bound() <= 1<<61
|
|
if !packed {
|
|
let type_align = machine::llalign_of_min(ccx, llty);
|
|
offset = roundup(offset, type_align);
|
|
}
|
|
// type_align is a power-of-2, so still offset < ccx.obj_size_bound()
|
|
// llsize_of_alloc(ccx, llty) is also less than ccx.obj_size_bound()
|
|
// so the sum is less than 1<<62 (and therefore can't overflow).
|
|
offset += machine::llsize_of_alloc(ccx, llty);
|
|
|
|
if offset >= ccx.obj_size_bound() {
|
|
ccx.report_overbig_object(scapegoat);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn union_size_and_align(sts: &[Struct]) -> (machine::llsize, machine::llalign) {
|
|
let size = sts.iter().map(|st| st.size).max().unwrap();
|
|
let align = sts.iter().map(|st| st.align).max().unwrap();
|
|
(roundup(size, align), align)
|
|
}
|
|
|
|
fn ensure_enum_fits_in_address_space<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
|
|
fields: &[Struct],
|
|
scapegoat: Ty<'tcx>) {
|
|
let (total_size, _) = union_size_and_align(fields);
|
|
|
|
if total_size >= ccx.obj_size_bound() {
|
|
ccx.report_overbig_object(scapegoat);
|
|
}
|
|
}
|
|
|
|
|
|
/// LLVM-level types are a little complicated.
|
|
///
|
|
/// C-like enums need to be actual ints, not wrapped in a struct,
|
|
/// because that changes the ABI on some platforms (see issue #10308).
|
|
///
|
|
/// For nominal types, in some cases, we need to use LLVM named structs
|
|
/// and fill in the actual contents in a second pass to prevent
|
|
/// unbounded recursion; see also the comments in `trans::type_of`.
|
|
pub fn type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, r: &Repr<'tcx>) -> Type {
|
|
generic_type_of(cx, r, None, false, false)
|
|
}
|
|
|
|
|
|
// Pass dst=true if the type you are passing is a DST. Yes, we could figure
|
|
// this out, but if you call this on an unsized type without realising it, you
|
|
// are going to get the wrong type (it will not include the unsized parts of it).
|
|
pub fn sizing_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
r: &Repr<'tcx>, dst: bool) -> Type {
|
|
generic_type_of(cx, r, None, true, dst)
|
|
}
|
|
|
|
pub fn incomplete_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
r: &Repr<'tcx>, name: &str) -> Type {
|
|
generic_type_of(cx, r, Some(name), false, false)
|
|
}
|
|
|
|
pub fn finish_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
r: &Repr<'tcx>, llty: &mut Type) {
|
|
match *r {
|
|
CEnum(..) | General(..) | UntaggedUnion(..) | RawNullablePointer { .. } => { }
|
|
Univariant(ref st) | StructWrappedNullablePointer { nonnull: ref st, .. } =>
|
|
llty.set_struct_body(&struct_llfields(cx, st, false, false),
|
|
st.packed)
|
|
}
|
|
}
|
|
|
|
fn generic_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
|
|
r: &Repr<'tcx>,
|
|
name: Option<&str>,
|
|
sizing: bool,
|
|
dst: bool) -> Type {
|
|
debug!("adt::generic_type_of r: {:?} name: {:?} sizing: {} dst: {}",
|
|
r, name, sizing, dst);
|
|
match *r {
|
|
CEnum(ity, _, _) => ll_inttype(cx, ity),
|
|
RawNullablePointer { nnty, .. } =>
|
|
type_of::sizing_type_of(cx, nnty),
|
|
StructWrappedNullablePointer { nonnull: ref st, .. } => {
|
|
match name {
|
|
None => {
|
|
Type::struct_(cx, &struct_llfields(cx, st, sizing, dst),
|
|
st.packed)
|
|
}
|
|
Some(name) => {
|
|
assert_eq!(sizing, false);
|
|
Type::named_struct(cx, name)
|
|
}
|
|
}
|
|
}
|
|
Univariant(ref st) => {
|
|
match name {
|
|
None => {
|
|
let fields = struct_llfields(cx, st, sizing, dst);
|
|
Type::struct_(cx, &fields, st.packed)
|
|
}
|
|
Some(name) => {
|
|
// Hypothesis: named_struct's can never need a
|
|
// drop flag. (... needs validation.)
|
|
assert_eq!(sizing, false);
|
|
Type::named_struct(cx, name)
|
|
}
|
|
}
|
|
}
|
|
UntaggedUnion(ref un) => {
|
|
// Use alignment-sized ints to fill all the union storage.
|
|
let (size, align) = (roundup(un.min_size, un.align), un.align);
|
|
|
|
let align_s = align as u64;
|
|
assert_eq!(size % align_s, 0); // Ensure division in align_units comes out evenly
|
|
let align_units = size / align_s;
|
|
let fill_ty = match align_s {
|
|
1 => Type::array(&Type::i8(cx), align_units),
|
|
2 => Type::array(&Type::i16(cx), align_units),
|
|
4 => Type::array(&Type::i32(cx), align_units),
|
|
8 if machine::llalign_of_min(cx, Type::i64(cx)) == 8 =>
|
|
Type::array(&Type::i64(cx), align_units),
|
|
a if a.count_ones() == 1 => Type::array(&Type::vector(&Type::i32(cx), a / 4),
|
|
align_units),
|
|
_ => bug!("unsupported union alignment: {}", align)
|
|
};
|
|
match name {
|
|
None => {
|
|
Type::struct_(cx, &[fill_ty], un.packed)
|
|
}
|
|
Some(name) => {
|
|
let mut llty = Type::named_struct(cx, name);
|
|
llty.set_struct_body(&[fill_ty], un.packed);
|
|
llty
|
|
}
|
|
}
|
|
}
|
|
General(ity, ref sts) => {
|
|
// We need a representation that has:
|
|
// * The alignment of the most-aligned field
|
|
// * The size of the largest variant (rounded up to that alignment)
|
|
// * No alignment padding anywhere any variant has actual data
|
|
// (currently matters only for enums small enough to be immediate)
|
|
// * The discriminant in an obvious place.
|
|
//
|
|
// So we start with the discriminant, pad it up to the alignment with
|
|
// more of its own type, then use alignment-sized ints to get the rest
|
|
// of the size.
|
|
//
|
|
// FIXME #10604: this breaks when vector types are present.
|
|
let (size, align) = union_size_and_align(&sts[..]);
|
|
let align_s = align as u64;
|
|
let discr_ty = ll_inttype(cx, ity);
|
|
let discr_size = machine::llsize_of_alloc(cx, discr_ty);
|
|
let padded_discr_size = roundup(discr_size, align);
|
|
assert_eq!(size % align_s, 0); // Ensure division in align_units comes out evenly
|
|
let align_units = (size - padded_discr_size) / align_s;
|
|
let fill_ty = match align_s {
|
|
1 => Type::array(&Type::i8(cx), align_units),
|
|
2 => Type::array(&Type::i16(cx), align_units),
|
|
4 => Type::array(&Type::i32(cx), align_units),
|
|
8 if machine::llalign_of_min(cx, Type::i64(cx)) == 8 =>
|
|
Type::array(&Type::i64(cx), align_units),
|
|
a if a.count_ones() == 1 => Type::array(&Type::vector(&Type::i32(cx), a / 4),
|
|
align_units),
|
|
_ => bug!("unsupported enum alignment: {}", align)
|
|
};
|
|
assert_eq!(machine::llalign_of_min(cx, fill_ty), align);
|
|
assert_eq!(padded_discr_size % discr_size, 0); // Ensure discr_ty can fill pad evenly
|
|
let fields: Vec<Type> =
|
|
[discr_ty,
|
|
Type::array(&discr_ty, (padded_discr_size - discr_size)/discr_size),
|
|
fill_ty].iter().cloned().collect();
|
|
match name {
|
|
None => {
|
|
Type::struct_(cx, &fields[..], false)
|
|
}
|
|
Some(name) => {
|
|
let mut llty = Type::named_struct(cx, name);
|
|
llty.set_struct_body(&fields[..], false);
|
|
llty
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn struct_llfields<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, st: &Struct<'tcx>,
|
|
sizing: bool, dst: bool) -> Vec<Type> {
|
|
if sizing {
|
|
st.fields.iter().filter(|&ty| !dst || type_is_sized(cx.tcx(), *ty))
|
|
.map(|&ty| type_of::sizing_type_of(cx, ty)).collect()
|
|
} else {
|
|
st.fields.iter().map(|&ty| type_of::in_memory_type_of(cx, ty)).collect()
|
|
}
|
|
}
|
|
|
|
/// Obtain a representation of the discriminant sufficient to translate
|
|
/// destructuring; this may or may not involve the actual discriminant.
|
|
pub fn trans_switch<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
|
|
r: &Repr<'tcx>,
|
|
scrutinee: ValueRef,
|
|
range_assert: bool)
|
|
-> (BranchKind, Option<ValueRef>) {
|
|
match *r {
|
|
CEnum(..) | General(..) |
|
|
RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
|
|
(BranchKind::Switch, Some(trans_get_discr(bcx, r, scrutinee, None, range_assert)))
|
|
}
|
|
Univariant(..) | UntaggedUnion(..) => {
|
|
// N.B.: Univariant means <= 1 enum variants (*not* == 1 variants).
|
|
(BranchKind::Single, None)
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn is_discr_signed<'tcx>(r: &Repr<'tcx>) -> bool {
|
|
match *r {
|
|
CEnum(ity, _, _) => ity.is_signed(),
|
|
General(ity, _) => ity.is_signed(),
|
|
Univariant(..) | UntaggedUnion(..) => false,
|
|
RawNullablePointer { .. } => false,
|
|
StructWrappedNullablePointer { .. } => false,
|
|
}
|
|
}
|
|
|
|
/// Obtain the actual discriminant of a value.
|
|
pub fn trans_get_discr<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, r: &Repr<'tcx>,
|
|
scrutinee: ValueRef, cast_to: Option<Type>,
|
|
range_assert: bool)
|
|
-> ValueRef {
|
|
debug!("trans_get_discr r: {:?}", r);
|
|
let val = match *r {
|
|
CEnum(ity, min, max) => {
|
|
load_discr(bcx, ity, scrutinee, min, max, range_assert)
|
|
}
|
|
General(ity, ref cases) => {
|
|
let ptr = StructGEP(bcx, scrutinee, 0);
|
|
load_discr(bcx, ity, ptr, Disr(0), Disr(cases.len() as u64 - 1),
|
|
range_assert)
|
|
}
|
|
Univariant(..) | UntaggedUnion(..) => C_u8(bcx.ccx(), 0),
|
|
RawNullablePointer { nndiscr, nnty, .. } => {
|
|
let cmp = if nndiscr == Disr(0) { IntEQ } else { IntNE };
|
|
let llptrty = type_of::sizing_type_of(bcx.ccx(), nnty);
|
|
ICmp(bcx, cmp, Load(bcx, scrutinee), C_null(llptrty), DebugLoc::None)
|
|
}
|
|
StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
|
|
struct_wrapped_nullable_bitdiscr(bcx, nndiscr, discrfield, scrutinee)
|
|
}
|
|
};
|
|
match cast_to {
|
|
None => val,
|
|
Some(llty) => if is_discr_signed(r) { SExt(bcx, val, llty) } else { ZExt(bcx, val, llty) }
|
|
}
|
|
}
|
|
|
|
fn struct_wrapped_nullable_bitdiscr(bcx: Block, nndiscr: Disr, discrfield: &DiscrField,
|
|
scrutinee: ValueRef) -> ValueRef {
|
|
let llptrptr = GEPi(bcx, scrutinee, &discrfield[..]);
|
|
let llptr = Load(bcx, llptrptr);
|
|
let cmp = if nndiscr == Disr(0) { IntEQ } else { IntNE };
|
|
ICmp(bcx, cmp, llptr, C_null(val_ty(llptr)), DebugLoc::None)
|
|
}
|
|
|
|
/// Helper for cases where the discriminant is simply loaded.
|
|
fn load_discr(bcx: Block, ity: IntType, ptr: ValueRef, min: Disr, max: Disr,
|
|
range_assert: bool)
|
|
-> 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 bits = bits as usize;
|
|
let mask = Disr(!0u64 >> (64 - bits));
|
|
// For a (max) discr of -1, max will be `-1 as usize`, which overflows.
|
|
// However, that is fine here (it would still represent the full range),
|
|
if max.wrapping_add(Disr(1)) & mask == min & mask || !range_assert {
|
|
// 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.0, max.0.wrapping_add(1), /* 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<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, r: &Repr, discr: Disr)
|
|
-> ValueRef {
|
|
match *r {
|
|
CEnum(ity, _, _) => {
|
|
C_integral(ll_inttype(bcx.ccx(), ity), discr.0, true)
|
|
}
|
|
General(ity, _) => {
|
|
C_integral(ll_inttype(bcx.ccx(), ity), discr.0, true)
|
|
}
|
|
Univariant(..) | UntaggedUnion(..) => {
|
|
bug!("no cases for univariants, structs or unions")
|
|
}
|
|
RawNullablePointer { .. } |
|
|
StructWrappedNullablePointer { .. } => {
|
|
assert!(discr == Disr(0) || discr == Disr(1));
|
|
C_bool(bcx.ccx(), discr != Disr(0))
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Set the discriminant for a new value of the given case of the given
|
|
/// representation.
|
|
pub fn trans_set_discr<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, r: &Repr<'tcx>,
|
|
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.0, true),
|
|
val);
|
|
}
|
|
General(ity, _) => {
|
|
Store(bcx, C_integral(ll_inttype(bcx.ccx(), ity), discr.0, true),
|
|
StructGEP(bcx, val, 0));
|
|
}
|
|
Univariant(_) => {
|
|
assert_eq!(discr, Disr(0));
|
|
}
|
|
UntaggedUnion(..) => {
|
|
assert_eq!(discr, Disr(0));
|
|
}
|
|
RawNullablePointer { nndiscr, nnty, ..} => {
|
|
if discr != nndiscr {
|
|
let llptrty = type_of::sizing_type_of(bcx.ccx(), nnty);
|
|
Store(bcx, C_null(llptrty), val);
|
|
}
|
|
}
|
|
StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
|
|
if discr != nndiscr {
|
|
let llptrptr = GEPi(bcx, val, &discrfield[..]);
|
|
let llptrty = val_ty(llptrptr).element_type();
|
|
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);
|
|
assert!(discr <= max);
|
|
},
|
|
attr::SignedInt(_) => {
|
|
assert!(min.0 as i64 <= discr.0 as i64);
|
|
assert!(discr.0 as i64 <= max.0 as i64);
|
|
},
|
|
}
|
|
}
|
|
|
|
/// Access a field, at a point when the value's case is known.
|
|
pub fn trans_field_ptr<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, r: &Repr<'tcx>,
|
|
val: MaybeSizedValue, discr: Disr, ix: usize) -> ValueRef {
|
|
trans_field_ptr_builder(&bcx.build(), r, val, discr, ix)
|
|
}
|
|
|
|
/// Access a field, at a point when the value's case is known.
|
|
pub fn trans_field_ptr_builder<'blk, 'tcx>(bcx: &BlockAndBuilder<'blk, 'tcx>,
|
|
r: &Repr<'tcx>,
|
|
val: MaybeSizedValue,
|
|
discr: Disr, ix: usize)
|
|
-> 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(..) => {
|
|
bug!("element access in C-like enum")
|
|
}
|
|
Univariant(ref st) => {
|
|
assert_eq!(discr, Disr(0));
|
|
struct_field_ptr(bcx, st, val, ix, false)
|
|
}
|
|
General(_, ref cases) => {
|
|
struct_field_ptr(bcx, &cases[discr.0 as usize], val, ix + 1, true)
|
|
}
|
|
UntaggedUnion(ref un) => {
|
|
let ty = type_of::in_memory_type_of(bcx.ccx(), un.fields[ix]);
|
|
if bcx.is_unreachable() { return C_undef(ty.ptr_to()); }
|
|
bcx.pointercast(val.value, ty.ptr_to())
|
|
}
|
|
RawNullablePointer { nndiscr, ref nullfields, .. } |
|
|
StructWrappedNullablePointer { nndiscr, ref nullfields, .. } if discr != nndiscr => {
|
|
// The unit-like case might have a nonzero number of unit-like fields.
|
|
// (e.d., Result of Either with (), as one side.)
|
|
let ty = type_of::type_of(bcx.ccx(), nullfields[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.
|
|
if bcx.is_unreachable() { return C_undef(ty.ptr_to()); }
|
|
bcx.pointercast(val.value, ty.ptr_to())
|
|
}
|
|
RawNullablePointer { nndiscr, nnty, .. } => {
|
|
assert_eq!(ix, 0);
|
|
assert_eq!(discr, nndiscr);
|
|
let ty = type_of::type_of(bcx.ccx(), nnty);
|
|
if bcx.is_unreachable() { return C_undef(ty.ptr_to()); }
|
|
bcx.pointercast(val.value, ty.ptr_to())
|
|
}
|
|
StructWrappedNullablePointer { ref nonnull, nndiscr, .. } => {
|
|
assert_eq!(discr, nndiscr);
|
|
struct_field_ptr(bcx, nonnull, val, ix, false)
|
|
}
|
|
}
|
|
}
|
|
|
|
fn struct_field_ptr<'blk, 'tcx>(bcx: &BlockAndBuilder<'blk, 'tcx>,
|
|
st: &Struct<'tcx>, val: MaybeSizedValue,
|
|
ix: usize, needs_cast: bool) -> ValueRef {
|
|
let ccx = bcx.ccx();
|
|
let fty = st.fields[ix];
|
|
let ll_fty = type_of::in_memory_type_of(bcx.ccx(), fty);
|
|
if bcx.is_unreachable() {
|
|
return C_undef(ll_fty.ptr_to());
|
|
}
|
|
|
|
let ptr_val = if needs_cast {
|
|
let fields = st.fields.iter().map(|&ty| {
|
|
type_of::in_memory_type_of(ccx, ty)
|
|
}).collect::<Vec<_>>();
|
|
let real_ty = Type::struct_(ccx, &fields[..], st.packed);
|
|
bcx.pointercast(val.value, real_ty.ptr_to())
|
|
} else {
|
|
val.value
|
|
};
|
|
|
|
// Simple case - we can just GEP the field
|
|
// * First field - Always aligned properly
|
|
// * Packed struct - There is no alignment padding
|
|
// * Field is sized - pointer is properly aligned already
|
|
if ix == 0 || st.packed || type_is_sized(bcx.tcx(), fty) {
|
|
return bcx.struct_gep(ptr_val, ix);
|
|
}
|
|
|
|
// If the type of the last field is [T] or str, then we don't need to do
|
|
// any adjusments
|
|
match fty.sty {
|
|
ty::TySlice(..) | ty::TyStr => {
|
|
return bcx.struct_gep(ptr_val, ix);
|
|
}
|
|
_ => ()
|
|
}
|
|
|
|
// There's no metadata available, log the case and just do the GEP.
|
|
if !val.has_meta() {
|
|
debug!("Unsized field `{}`, of `{:?}` has no metadata for adjustment",
|
|
ix, Value(ptr_val));
|
|
return bcx.struct_gep(ptr_val, ix);
|
|
}
|
|
|
|
let dbloc = DebugLoc::None;
|
|
|
|
// We need to get the pointer manually now.
|
|
// We do this by casting to a *i8, then offsetting it by the appropriate amount.
|
|
// We do this instead of, say, simply adjusting the pointer from the result of a GEP
|
|
// because the field may have an arbitrary alignment in the LLVM representation
|
|
// anyway.
|
|
//
|
|
// To demonstrate:
|
|
// struct Foo<T: ?Sized> {
|
|
// x: u16,
|
|
// y: T
|
|
// }
|
|
//
|
|
// The type Foo<Foo<Trait>> is represented in LLVM as { u16, { u16, u8 }}, meaning that
|
|
// the `y` field has 16-bit alignment.
|
|
|
|
let meta = val.meta;
|
|
|
|
// Calculate the unaligned offset of the unsized field.
|
|
let mut offset = 0;
|
|
for &ty in &st.fields[0..ix] {
|
|
let llty = type_of::sizing_type_of(ccx, ty);
|
|
let type_align = type_of::align_of(ccx, ty);
|
|
offset = roundup(offset, type_align);
|
|
offset += machine::llsize_of_alloc(ccx, llty);
|
|
}
|
|
let unaligned_offset = C_uint(bcx.ccx(), offset);
|
|
|
|
// Get the alignment of the field
|
|
let (_, align) = glue::size_and_align_of_dst(bcx, fty, meta);
|
|
|
|
// Bump the unaligned offset up to the appropriate alignment using the
|
|
// following expression:
|
|
//
|
|
// (unaligned offset + (align - 1)) & -align
|
|
|
|
// Calculate offset
|
|
dbloc.apply(bcx.fcx());
|
|
let align_sub_1 = bcx.sub(align, C_uint(bcx.ccx(), 1u64));
|
|
let offset = bcx.and(bcx.add(unaligned_offset, align_sub_1),
|
|
bcx.neg(align));
|
|
|
|
debug!("struct_field_ptr: DST field offset: {:?}", Value(offset));
|
|
|
|
// Cast and adjust pointer
|
|
let byte_ptr = bcx.pointercast(ptr_val, Type::i8p(bcx.ccx()));
|
|
let byte_ptr = bcx.gep(byte_ptr, &[offset]);
|
|
|
|
// Finally, cast back to the type expected
|
|
let ll_fty = type_of::in_memory_type_of(bcx.ccx(), fty);
|
|
debug!("struct_field_ptr: Field type is {:?}", ll_fty);
|
|
bcx.pointercast(byte_ptr, ll_fty.ptr_to())
|
|
}
|
|
|
|
/// 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 Windows. 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<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, r: &Repr<'tcx>, 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.0, true)
|
|
}
|
|
General(ity, ref cases) => {
|
|
let case = &cases[discr.0 as usize];
|
|
let (max_sz, _) = union_size_and_align(&cases[..]);
|
|
let lldiscr = C_integral(ll_inttype(ccx, ity), discr.0 as u64, true);
|
|
let mut f = vec![lldiscr];
|
|
f.extend_from_slice(vals);
|
|
let mut contents = build_const_struct(ccx, case, &f[..]);
|
|
contents.extend_from_slice(&[padding(ccx, max_sz - case.size)]);
|
|
C_struct(ccx, &contents[..], false)
|
|
}
|
|
UntaggedUnion(ref un) => {
|
|
assert_eq!(discr, Disr(0));
|
|
let contents = build_const_union(ccx, un, vals[0]);
|
|
C_struct(ccx, &contents, un.packed)
|
|
}
|
|
Univariant(ref st) => {
|
|
assert_eq!(discr, Disr(0));
|
|
let contents = build_const_struct(ccx, st, vals);
|
|
C_struct(ccx, &contents[..], st.packed)
|
|
}
|
|
RawNullablePointer { nndiscr, nnty, .. } => {
|
|
if discr == nndiscr {
|
|
assert_eq!(vals.len(), 1);
|
|
vals[0]
|
|
} else {
|
|
C_null(type_of::sizing_type_of(ccx, nnty))
|
|
}
|
|
}
|
|
StructWrappedNullablePointer { ref nonnull, nndiscr, .. } => {
|
|
if discr == nndiscr {
|
|
C_struct(ccx, &build_const_struct(ccx,
|
|
nonnull,
|
|
vals),
|
|
false)
|
|
} else {
|
|
let vals = nonnull.fields.iter().map(|&ty| {
|
|
// Always use null even if it's not the `discrfield`th
|
|
// field; see #8506.
|
|
C_null(type_of::sizing_type_of(ccx, ty))
|
|
}).collect::<Vec<ValueRef>>();
|
|
C_struct(ccx, &build_const_struct(ccx,
|
|
nonnull,
|
|
&vals[..]),
|
|
false)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Compute struct field offsets relative to struct begin.
|
|
fn compute_struct_field_offsets<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
|
|
st: &Struct<'tcx>) -> Vec<u64> {
|
|
let mut offsets = vec!();
|
|
|
|
let mut offset = 0;
|
|
for &ty in &st.fields {
|
|
let llty = type_of::sizing_type_of(ccx, ty);
|
|
if !st.packed {
|
|
let type_align = type_of::align_of(ccx, ty);
|
|
offset = roundup(offset, type_align);
|
|
}
|
|
offsets.push(offset);
|
|
offset += machine::llsize_of_alloc(ccx, llty);
|
|
}
|
|
assert_eq!(st.fields.len(), offsets.len());
|
|
offsets
|
|
}
|
|
|
|
/// 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<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
|
|
st: &Struct<'tcx>, vals: &[ValueRef])
|
|
-> Vec<ValueRef> {
|
|
assert_eq!(vals.len(), st.fields.len());
|
|
|
|
let target_offsets = compute_struct_field_offsets(ccx, st);
|
|
|
|
// offset of current value
|
|
let mut offset = 0;
|
|
let mut cfields = Vec::new();
|
|
for (&val, target_offset) in vals.iter().zip(target_offsets) {
|
|
if !st.packed {
|
|
let val_align = machine::llalign_of_min(ccx, val_ty(val));
|
|
offset = roundup(offset, val_align);
|
|
}
|
|
if offset != target_offset {
|
|
cfields.push(padding(ccx, target_offset - offset));
|
|
offset = target_offset;
|
|
}
|
|
assert!(!is_undef(val));
|
|
cfields.push(val);
|
|
offset += machine::llsize_of_alloc(ccx, val_ty(val));
|
|
}
|
|
|
|
assert!(st.sized && offset <= st.size);
|
|
if offset != st.size {
|
|
cfields.push(padding(ccx, st.size - offset));
|
|
}
|
|
|
|
cfields
|
|
}
|
|
|
|
fn build_const_union<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
|
|
un: &Union<'tcx>,
|
|
field_val: ValueRef)
|
|
-> Vec<ValueRef> {
|
|
let mut cfields = vec![field_val];
|
|
|
|
let offset = machine::llsize_of_alloc(ccx, val_ty(field_val));
|
|
let size = roundup(un.min_size, un.align);
|
|
if offset != size {
|
|
cfields.push(padding(ccx, size - offset));
|
|
}
|
|
|
|
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: u32) -> u64 { let a = a as u64; ((x + (a - 1)) / a) * a }
|
|
|
|
/// 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(r: &Repr, val: ValueRef, _discr: Disr,
|
|
ix: usize) -> ValueRef {
|
|
match *r {
|
|
CEnum(..) => bug!("element access in C-like enum const"),
|
|
Univariant(..) => const_struct_field(val, ix),
|
|
UntaggedUnion(..) => const_struct_field(val, 0),
|
|
General(..) => const_struct_field(val, ix + 1),
|
|
RawNullablePointer { .. } => {
|
|
assert_eq!(ix, 0);
|
|
val
|
|
},
|
|
StructWrappedNullablePointer{ .. } => const_struct_field(val, ix)
|
|
}
|
|
}
|
|
|
|
/// Extract field of struct-like const, skipping our alignment padding.
|
|
fn const_struct_field(val: ValueRef, ix: usize) -> 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(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;
|
|
}
|
|
}
|