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Rollup merge of rust-lang#39595 - camlorn:structured_repr, r=eddyb
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Make reprs use a structured representation instead of a slice

This is needed for `-z reorder-fields`.  The old design uses a slice taken from HIR, plus a cache that lazily parses.  The new design stores it directly in the `AdtDef` as a `ReprOptions`.  We're doing this now because we need to be able to add reprs that don't necessarily exist in HIR for `-z reorder-fields`, but it needs to happen anyway.

`lookup_repr_hints` should be mostly deprecated.  I want to remove it from `layout` before closing this, unless people think that should be a separate PR.  The `[WIP]` is because of this.  The problem with closing this as-is is that the code here isn't actually testable until some parts of the compiler start using it.

r? @eddyb
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@frewsxcv
frewsxcv committed Feb 9, 2017
2 parents b0e46f0 + c3b64cf commit 15decb8
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Showing 7 changed files with 116 additions and 94 deletions.
6 changes: 4 additions & 2 deletions src/librustc/ty/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ use middle::resolve_lifetime;
use middle::stability;
use mir::Mir;
use ty::subst::{Kind, Substs};
use ty::ReprOptions;
use traits;
use ty::{self, TraitRef, Ty, TypeAndMut};
use ty::{TyS, TypeVariants, Slice};
Expand Down Expand Up @@ -672,9 +673,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
pub fn alloc_adt_def(self,
did: DefId,
kind: AdtKind,
variants: Vec<ty::VariantDef>)
variants: Vec<ty::VariantDef>,
repr: ReprOptions)
-> &'gcx ty::AdtDef {
let def = ty::AdtDef::new(self, did, kind, variants);
let def = ty::AdtDef::new(self, did, kind, variants, repr);
self.global_arenas.adt_def.alloc(def)
}

Expand Down
102 changes: 39 additions & 63 deletions src/librustc/ty/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ pub use self::Primitive::*;
use infer::InferCtxt;
use session::Session;
use traits;
use ty::{self, Ty, TyCtxt, TypeFoldable};
use ty::{self, Ty, TyCtxt, TypeFoldable, ReprOptions};

use syntax::ast::{FloatTy, IntTy, UintTy};
use syntax::attr;
Expand Down Expand Up @@ -437,7 +437,7 @@ impl Integer {
/// signed discriminant range and #[repr] attribute.
/// N.B.: u64 values above i64::MAX will be treated as signed, but
/// that shouldn't affect anything, other than maybe debuginfo.
fn repr_discr(tcx: TyCtxt, ty: Ty, hints: &[attr::ReprAttr], min: i64, max: i64)
fn repr_discr(tcx: TyCtxt, ty: Ty, repr: &ReprOptions, min: i64, max: i64)
-> (Integer, bool) {
// Theoretically, negative values could be larger in unsigned representation
// than the unsigned representation of the signed minimum. However, if there
Expand All @@ -449,34 +449,24 @@ impl Integer {
let mut min_from_extern = None;
let min_default = I8;

for &r in hints.iter() {
match r {
attr::ReprInt(ity) => {
let discr = Integer::from_attr(&tcx.data_layout, ity);
let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
if discr < fit {
bug!("Integer::repr_discr: `#[repr]` hint too small for \
discriminant range of enum `{}", ty)
}
return (discr, ity.is_signed());
}
attr::ReprExtern => {
match &tcx.sess.target.target.arch[..] {
// WARNING: the ARM EABI has two variants; the one corresponding
// to `at_least == I32` appears to be used on Linux and NetBSD,
// but some systems may use the variant corresponding to no
// lower bound. However, we don't run on those yet...?
"arm" => min_from_extern = Some(I32),
_ => min_from_extern = Some(I32),
}
}
attr::ReprAny => {},
attr::ReprPacked => {
bug!("Integer::repr_discr: found #[repr(packed)] on enum `{}", ty);
}
attr::ReprSimd => {
bug!("Integer::repr_discr: found #[repr(simd)] on enum `{}", ty);
}
if let Some(ity) = repr.int {
let discr = Integer::from_attr(&tcx.data_layout, ity);
let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
if discr < fit {
bug!("Integer::repr_discr: `#[repr]` hint too small for \
discriminant range of enum `{}", ty)
}
return (discr, ity.is_signed());
}

if repr.c {
match &tcx.sess.target.target.arch[..] {
// WARNING: the ARM EABI has two variants; the one corresponding
// to `at_least == I32` appears to be used on Linux and NetBSD,
// but some systems may use the variant corresponding to no
// lower bound. However, we don't run on those yet...?
"arm" => min_from_extern = Some(I32),
_ => min_from_extern = Some(I32),
}
}

Expand Down Expand Up @@ -568,9 +558,9 @@ enum StructKind {
impl<'a, 'gcx, 'tcx> Struct {
// FIXME(camlorn): reprs need a better representation to deal with multiple reprs on one type.
fn new(dl: &TargetDataLayout, fields: &Vec<&'a Layout>,
reprs: &[attr::ReprAttr], kind: StructKind,
repr: &ReprOptions, kind: StructKind,
scapegoat: Ty<'gcx>) -> Result<Struct, LayoutError<'gcx>> {
let packed = reprs.contains(&attr::ReprPacked);
let packed = repr.packed;
let mut ret = Struct {
align: if packed { dl.i8_align } else { dl.aggregate_align },
packed: packed,
Expand All @@ -580,27 +570,16 @@ impl<'a, 'gcx, 'tcx> Struct {
min_size: Size::from_bytes(0),
};

// Anything with ReprExtern or ReprPacked doesn't optimize.
// Anything with repr(C) or repr(packed) doesn't optimize.
// Neither do 1-member and 2-member structs.
// In addition, code in trans assume that 2-element structs can become pairs.
// It's easier to just short-circuit here.
let mut can_optimize = fields.len() > 2 || StructKind::EnumVariant == kind;
if can_optimize {
// This exhaustive match makes new reprs force the adder to modify this function.
// Otherwise, things can silently break.
// Note the inversion, return true to stop optimizing.
can_optimize = !reprs.iter().any(|r| {
match *r {
attr::ReprAny | attr::ReprInt(_) => false,
attr::ReprExtern | attr::ReprPacked => true,
attr::ReprSimd => bug!("Simd vectors should be represented as layout::Vector")
}
});
}
let mut can_optimize = (fields.len() > 2 || StructKind::EnumVariant == kind)
&& ! (repr.c || repr.packed);

// Disable field reordering until we can decide what to do.
// The odd pattern here avoids a warning about the value never being read.
if can_optimize { can_optimize = false }
if can_optimize { can_optimize = false; }

let (optimize, sort_ascending) = match kind {
StructKind::AlwaysSizedUnivariant => (can_optimize, false),
Expand Down Expand Up @@ -1092,7 +1071,7 @@ impl<'a, 'gcx, 'tcx> Layout {

// The never type.
ty::TyNever => Univariant {
variant: Struct::new(dl, &vec![], &[],
variant: Struct::new(dl, &vec![], &ReprOptions::default(),
StructKind::AlwaysSizedUnivariant, ty)?,
non_zero: false
},
Expand Down Expand Up @@ -1135,12 +1114,12 @@ impl<'a, 'gcx, 'tcx> Layout {
ty::TyFnDef(..) => {
Univariant {
variant: Struct::new(dl, &vec![],
&[], StructKind::AlwaysSizedUnivariant, ty)?,
&ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?,
non_zero: false
}
}
ty::TyDynamic(..) => {
let mut unit = Struct::new(dl, &vec![], &[],
let mut unit = Struct::new(dl, &vec![], &ReprOptions::default(),
StructKind::AlwaysSizedUnivariant, ty)?;
unit.sized = false;
Univariant { variant: unit, non_zero: false }
Expand All @@ -1152,7 +1131,7 @@ impl<'a, 'gcx, 'tcx> Layout {
let st = Struct::new(dl,
&tys.map(|ty| ty.layout(infcx))
.collect::<Result<Vec<_>, _>>()?,
&[],
&ReprOptions::default(),
StructKind::AlwaysSizedUnivariant, ty)?;
Univariant { variant: st, non_zero: false }
}
Expand All @@ -1163,7 +1142,7 @@ impl<'a, 'gcx, 'tcx> Layout {
let st = Struct::new(dl,
&tys.iter().map(|ty| ty.layout(infcx))
.collect::<Result<Vec<_>, _>>()?,
&[], StructKind::AlwaysSizedUnivariant, ty)?;
&ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?;
Univariant { variant: st, non_zero: false }
}

Expand All @@ -1187,16 +1166,13 @@ impl<'a, 'gcx, 'tcx> Layout {

// ADTs.
ty::TyAdt(def, substs) => {
let hints = &tcx.lookup_repr_hints(def.did)[..];

if def.variants.is_empty() {
// Uninhabitable; represent as unit
// (Typechecking will reject discriminant-sizing attrs.)
assert_eq!(hints.len(), 0);

return success(Univariant {
variant: Struct::new(dl, &vec![],
&hints[..], StructKind::AlwaysSizedUnivariant, ty)?,
&def.repr, StructKind::AlwaysSizedUnivariant, ty)?,
non_zero: false
});
}
Expand All @@ -1219,7 +1195,7 @@ impl<'a, 'gcx, 'tcx> Layout {

// FIXME: should handle i128? signed-value based impl is weird and hard to
// grok.
let (discr, signed) = Integer::repr_discr(tcx, ty, &hints[..],
let (discr, signed) = Integer::repr_discr(tcx, ty, &def.repr,
min,
max);
return success(CEnum {
Expand All @@ -1232,7 +1208,7 @@ impl<'a, 'gcx, 'tcx> Layout {
});
}

if !def.is_enum() || def.variants.len() == 1 && hints.is_empty() {
if !def.is_enum() || def.variants.len() == 1 {
// Struct, or union, or univariant enum equivalent to a struct.
// (Typechecking will reject discriminant-sizing attrs.)

Expand All @@ -1259,7 +1235,7 @@ impl<'a, 'gcx, 'tcx> Layout {
un.extend(dl, fields.iter().map(|&f| Ok(f)), ty)?;
UntaggedUnion { variants: un }
} else {
let st = Struct::new(dl, &fields, &hints[..],
let st = Struct::new(dl, &fields, &def.repr,
kind, ty)?;
let non_zero = Some(def.did) == tcx.lang_items.non_zero();
Univariant { variant: st, non_zero: non_zero }
Expand All @@ -1282,7 +1258,7 @@ impl<'a, 'gcx, 'tcx> Layout {
v.fields.iter().map(|field| field.ty(tcx, substs)).collect::<Vec<_>>()
}).collect::<Vec<_>>();

if variants.len() == 2 && hints.is_empty() {
if variants.len() == 2 && !def.repr.c {
// Nullable pointer optimization
for discr in 0..2 {
let other_fields = variants[1 - discr].iter().map(|ty| {
Expand Down Expand Up @@ -1315,7 +1291,7 @@ impl<'a, 'gcx, 'tcx> Layout {
let st = Struct::new(dl,
&variants[discr].iter().map(|ty| ty.layout(infcx))
.collect::<Result<Vec<_>, _>>()?,
&hints[..], StructKind::AlwaysSizedUnivariant, ty)?;
&def.repr, StructKind::AlwaysSizedUnivariant, ty)?;

// We have to fix the last element of path here.
let mut i = *path.last().unwrap();
Expand All @@ -1338,7 +1314,7 @@ impl<'a, 'gcx, 'tcx> Layout {
// The general case.
let discr_max = (variants.len() - 1) as i64;
assert!(discr_max >= 0);
let (min_ity, _) = Integer::repr_discr(tcx, ty, &hints[..], 0, discr_max);
let (min_ity, _) = Integer::repr_discr(tcx, ty, &def.repr, 0, discr_max);

let mut align = dl.aggregate_align;
let mut size = Size::from_bytes(0);
Expand All @@ -1356,7 +1332,7 @@ impl<'a, 'gcx, 'tcx> Layout {
fields.insert(0, &discr);
let st = Struct::new(dl,
&fields,
&hints[..], StructKind::EnumVariant, ty)?;
&def.repr, StructKind::EnumVariant, ty)?;
// Find the first field we can't move later
// to make room for a larger discriminant.
// It is important to skip the first field.
Expand Down
33 changes: 31 additions & 2 deletions src/librustc/ty/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1327,7 +1327,8 @@ pub struct AdtDef {
pub did: DefId,
pub variants: Vec<VariantDef>,
destructor: Cell<Option<DefId>>,
flags: Cell<AdtFlags>
flags: Cell<AdtFlags>,
pub repr: ReprOptions,
}

impl PartialEq for AdtDef {
Expand Down Expand Up @@ -1356,11 +1357,38 @@ impl<'tcx> serialize::UseSpecializedDecodable for &'tcx AdtDef {}
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum AdtKind { Struct, Union, Enum }

/// Represents the repr options provided by the user,
#[derive(Copy, Clone, Eq, PartialEq, RustcEncodable, RustcDecodable, Default)]
pub struct ReprOptions {
pub c: bool,
pub packed: bool,
pub simd: bool,
pub int: Option<attr::IntType>,
}

impl ReprOptions {
pub fn new<'a, 'gcx, 'tcx>(tcx: &TyCtxt<'a, 'gcx, 'tcx>, did: DefId) -> ReprOptions {
let mut ret = ReprOptions::default();
let attrs = tcx.lookup_repr_hints(did);
for r in attrs.iter() {
match *r {
attr::ReprExtern => ret.c = true,
attr::ReprPacked => ret.packed = true,
attr::ReprSimd => ret.simd = true,
attr::ReprInt(i) => ret.int = Some(i),
attr::ReprAny => (),
}
}
ret
}
}

impl<'a, 'gcx, 'tcx> AdtDef {
fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>,
did: DefId,
kind: AdtKind,
variants: Vec<VariantDef>) -> Self {
variants: Vec<VariantDef>,
repr: ReprOptions) -> Self {
let mut flags = AdtFlags::NO_ADT_FLAGS;
let attrs = tcx.get_attrs(did);
if attr::contains_name(&attrs, "fundamental") {
Expand All @@ -1385,6 +1413,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
variants: variants,
flags: Cell::new(flags),
destructor: Cell::new(None),
repr: repr,
}
}

Expand Down
28 changes: 14 additions & 14 deletions src/librustc_metadata/decoder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -425,8 +425,8 @@ impl<'tcx> EntryKind<'tcx> {
EntryKind::ForeignImmStatic => Def::Static(did, false),
EntryKind::MutStatic |
EntryKind::ForeignMutStatic => Def::Static(did, true),
EntryKind::Struct(_) => Def::Struct(did),
EntryKind::Union(_) => Def::Union(did),
EntryKind::Struct(_, _) => Def::Struct(did),
EntryKind::Union(_, _) => Def::Union(did),
EntryKind::Fn(_) |
EntryKind::ForeignFn(_) => Def::Fn(did),
EntryKind::Method(_) => Def::Method(did),
Expand All @@ -435,7 +435,7 @@ impl<'tcx> EntryKind<'tcx> {
EntryKind::Mod(_) => Def::Mod(did),
EntryKind::Variant(_) => Def::Variant(did),
EntryKind::Trait(_) => Def::Trait(did),
EntryKind::Enum => Def::Enum(did),
EntryKind::Enum(_) => Def::Enum(did),
EntryKind::MacroDef(_) => Def::Macro(did),

EntryKind::ForeignMod |
Expand Down Expand Up @@ -519,8 +519,8 @@ impl<'a, 'tcx> CrateMetadata {
-> (ty::VariantDef, Option<DefIndex>) {
let data = match item.kind {
EntryKind::Variant(data) |
EntryKind::Struct(data) |
EntryKind::Union(data) => data.decode(self),
EntryKind::Struct(data, _) |
EntryKind::Union(data, _) => data.decode(self),
_ => bug!(),
};

Expand All @@ -547,7 +547,7 @@ impl<'a, 'tcx> CrateMetadata {
let item = self.entry(item_id);
let did = self.local_def_id(item_id);
let mut ctor_index = None;
let variants = if let EntryKind::Enum = item.kind {
let variants = if let EntryKind::Enum(_) = item.kind {
item.children
.decode(self)
.map(|index| {
Expand All @@ -561,14 +561,14 @@ impl<'a, 'tcx> CrateMetadata {
ctor_index = struct_ctor;
vec![variant]
};
let kind = match item.kind {
EntryKind::Enum => ty::AdtKind::Enum,
EntryKind::Struct(_) => ty::AdtKind::Struct,
EntryKind::Union(_) => ty::AdtKind::Union,
let (kind, repr) = match item.kind {
EntryKind::Enum(repr) => (ty::AdtKind::Enum, repr),
EntryKind::Struct(_, repr) => (ty::AdtKind::Struct, repr),
EntryKind::Union(_, repr) => (ty::AdtKind::Union, repr),
_ => bug!("get_adt_def called on a non-ADT {:?}", did),
};

let adt = tcx.alloc_adt_def(did, kind, variants);
let adt = tcx.alloc_adt_def(did, kind, variants, repr);
if let Some(ctor_index) = ctor_index {
// Make adt definition available through constructor id as well.
tcx.adt_defs.borrow_mut().insert(self.local_def_id(ctor_index), adt);
Expand Down Expand Up @@ -881,16 +881,16 @@ impl<'a, 'tcx> CrateMetadata {

pub fn get_ctor_kind(&self, node_id: DefIndex) -> CtorKind {
match self.entry(node_id).kind {
EntryKind::Struct(data) |
EntryKind::Union(data) |
EntryKind::Struct(data, _) |
EntryKind::Union(data, _) |
EntryKind::Variant(data) => data.decode(self).ctor_kind,
_ => CtorKind::Fictive,
}
}

pub fn get_struct_ctor_def_id(&self, node_id: DefIndex) -> Option<DefId> {
match self.entry(node_id).kind {
EntryKind::Struct(data) => {
EntryKind::Struct(data, _) => {
data.decode(self).struct_ctor.map(|index| self.local_def_id(index))
}
_ => None,
Expand Down
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