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Auto merge of #46436 - eddyb:unpacked, r=arielb1,oli-obk
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Detect unaligned fields via `aggregate.align < field.align`, instead of a `packed` flag.

Closes #46423. cc @oli-obk
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bors committed Dec 17, 2017
2 parents af57ace + 799a83c commit 3cc68ba
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Showing 26 changed files with 518 additions and 781 deletions.
9 changes: 4 additions & 5 deletions src/librustc/mir/interpret/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,14 +10,13 @@ mod value;

pub use self::error::{EvalError, EvalResult, EvalErrorKind};

pub use self::value::{PrimVal, PrimValKind, Value, Pointer, PtrAndAlign, bytes_to_f32, bytes_to_f64};
pub use self::value::{PrimVal, PrimValKind, Value, Pointer, bytes_to_f32, bytes_to_f64};

use std::collections::BTreeMap;
use ty::layout::HasDataLayout;
use std::fmt;
use ty::layout;
use mir;
use ty;
use ty::layout::{self, Align, HasDataLayout};
use middle::region;
use std::iter;

Expand Down Expand Up @@ -166,7 +165,7 @@ pub struct Allocation {
/// Denotes undefined memory. Reading from undefined memory is forbidden in miri
pub undef_mask: UndefMask,
/// The alignment of the allocation to detect unaligned reads.
pub align: u64,
pub align: Align,
}

impl Allocation {
Expand All @@ -177,7 +176,7 @@ impl Allocation {
bytes: slice.to_owned(),
relocations: BTreeMap::new(),
undef_mask,
align: 1,
align: Align::from_bytes(1, 1).unwrap(),
}
}
}
Expand Down
30 changes: 2 additions & 28 deletions src/librustc/mir/interpret/value.rs
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Original file line number Diff line number Diff line change
@@ -1,30 +1,11 @@
#![allow(unknown_lints)]

use ty::layout::HasDataLayout;
use ty::layout::{Align, HasDataLayout};

use super::{EvalResult, MemoryPointer, PointerArithmetic};
use syntax::ast::FloatTy;
use rustc_const_math::ConstFloat;

#[derive(Copy, Clone, Debug)]
pub struct PtrAndAlign {
pub ptr: Pointer,
/// Remember whether this place is *supposed* to be aligned.
pub aligned: bool,
}

impl PtrAndAlign {
pub fn to_ptr<'tcx>(self) -> EvalResult<'tcx, MemoryPointer> {
self.ptr.to_ptr()
}
pub fn offset<'tcx, C: HasDataLayout>(self, i: u64, cx: C) -> EvalResult<'tcx, Self> {
Ok(PtrAndAlign {
ptr: self.ptr.offset(i, cx)?,
aligned: self.aligned,
})
}
}

pub fn bytes_to_f32(bits: u128) -> ConstFloat {
ConstFloat {
bits,
Expand All @@ -50,7 +31,7 @@ pub fn bytes_to_f64(bits: u128) -> ConstFloat {
/// operations and fat pointers. This idea was taken from rustc's trans.
#[derive(Clone, Copy, Debug)]
pub enum Value {
ByRef(PtrAndAlign),
ByRef(Pointer, Align),
ByVal(PrimVal),
ByValPair(PrimVal, PrimVal),
}
Expand Down Expand Up @@ -182,13 +163,6 @@ pub enum PrimValKind {
Char,
}

impl<'a, 'tcx: 'a> Value {
#[inline]
pub fn by_ref(ptr: Pointer) -> Self {
Value::ByRef(PtrAndAlign { ptr, aligned: true })
}
}

impl<'tcx> PrimVal {
pub fn from_u128(n: u128) -> Self {
PrimVal::Bytes(n)
Expand Down
6 changes: 3 additions & 3 deletions src/librustc/ty/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -895,7 +895,7 @@ pub struct InterpretInterner<'tcx> {
/// Allows checking whether a constant already has an allocation
///
/// The pointers are to the beginning of an `alloc_by_id` allocation
alloc_cache: FxHashMap<interpret::GlobalId<'tcx>, interpret::PtrAndAlign>,
alloc_cache: FxHashMap<interpret::GlobalId<'tcx>, interpret::Pointer>,

/// A cache for basic byte allocations keyed by their contents. This is used to deduplicate
/// allocations for string and bytestring literals.
Expand Down Expand Up @@ -931,14 +931,14 @@ impl<'tcx> InterpretInterner<'tcx> {
pub fn get_cached(
&self,
global_id: interpret::GlobalId<'tcx>,
) -> Option<interpret::PtrAndAlign> {
) -> Option<interpret::Pointer> {
self.alloc_cache.get(&global_id).cloned()
}

pub fn cache(
&mut self,
global_id: interpret::GlobalId<'tcx>,
ptr: interpret::PtrAndAlign,
ptr: interpret::Pointer,
) {
if let Some(old) = self.alloc_cache.insert(global_id, ptr) {
bug!("tried to cache {:?}, but was already existing as {:#?}", global_id, old);
Expand Down
63 changes: 11 additions & 52 deletions src/librustc/ty/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -778,7 +778,6 @@ pub enum Abi {
Aggregate {
/// If true, the size is exact, otherwise it's only a lower bound.
sized: bool,
packed: bool
}
}

Expand All @@ -790,18 +789,7 @@ impl Abi {
Abi::Scalar(_) |
Abi::ScalarPair(..) |
Abi::Vector { .. } => false,
Abi::Aggregate { sized, .. } => !sized
}
}

/// Returns true if the fields of the layout are packed.
pub fn is_packed(&self) -> bool {
match *self {
Abi::Uninhabited |
Abi::Scalar(_) |
Abi::ScalarPair(..) |
Abi::Vector { .. } => false,
Abi::Aggregate { packed, .. } => packed
Abi::Aggregate { sized } => !sized
}
}
}
Expand Down Expand Up @@ -1077,10 +1065,7 @@ impl<'a, 'tcx> LayoutDetails {
}

let size = min_size.abi_align(align);
let mut abi = Abi::Aggregate {
sized,
packed
};
let mut abi = Abi::Aggregate { sized };

// Unpack newtype ABIs and find scalar pairs.
if sized && size.bytes() > 0 {
Expand Down Expand Up @@ -1254,10 +1239,7 @@ impl<'a, 'tcx> LayoutDetails {
stride: element.size,
count
},
abi: Abi::Aggregate {
sized: true,
packed: false
},
abi: Abi::Aggregate { sized: true },
align: element.align,
size
})
Expand All @@ -1270,10 +1252,7 @@ impl<'a, 'tcx> LayoutDetails {
stride: element.size,
count: 0
},
abi: Abi::Aggregate {
sized: false,
packed: false
},
abi: Abi::Aggregate { sized: false },
align: element.align,
size: Size::from_bytes(0)
})
Expand All @@ -1285,10 +1264,7 @@ impl<'a, 'tcx> LayoutDetails {
stride: Size::from_bytes(1),
count: 0
},
abi: Abi::Aggregate {
sized: false,
packed: false
},
abi: Abi::Aggregate { sized: false },
align: dl.i8_align,
size: Size::from_bytes(0)
})
Expand All @@ -1302,7 +1278,7 @@ impl<'a, 'tcx> LayoutDetails {
let mut unit = univariant_uninterned(&[], &ReprOptions::default(),
StructKind::AlwaysSized)?;
match unit.abi {
Abi::Aggregate { ref mut sized, .. } => *sized = false,
Abi::Aggregate { ref mut sized } => *sized = false,
_ => bug!()
}
tcx.intern_layout(unit)
Expand Down Expand Up @@ -1418,10 +1394,7 @@ impl<'a, 'tcx> LayoutDetails {
return Ok(tcx.intern_layout(LayoutDetails {
variants: Variants::Single { index: 0 },
fields: FieldPlacement::Union(variants[0].len()),
abi: Abi::Aggregate {
sized: true,
packed
},
abi: Abi::Aggregate { sized: true },
align,
size: size.abi_align(align)
}));
Expand Down Expand Up @@ -1525,15 +1498,10 @@ impl<'a, 'tcx> LayoutDetails {
let abi = if offset.bytes() == 0 && niche.value.size(dl) == size {
Abi::Scalar(niche.clone())
} else {
let mut packed = st[i].abi.is_packed();
if offset.abi_align(niche_align) != offset {
packed = true;
niche_align = dl.i8_align;
}
Abi::Aggregate {
sized: true,
packed
}
Abi::Aggregate { sized: true }
};
align = align.max(niche_align);

Expand Down Expand Up @@ -1681,10 +1649,7 @@ impl<'a, 'tcx> LayoutDetails {
let abi = if discr.value.size(dl) == size {
Abi::Scalar(discr.clone())
} else {
Abi::Aggregate {
sized: true,
packed: false
}
Abi::Aggregate { sized: true }
};
tcx.intern_layout(LayoutDetails {
variants: Variants::Tagged {
Expand Down Expand Up @@ -2277,19 +2242,14 @@ impl<'a, 'tcx> TyLayout<'tcx> {
self.abi.is_unsized()
}

/// Returns true if the fields of the layout are packed.
pub fn is_packed(&self) -> bool {
self.abi.is_packed()
}

/// Returns true if the type is a ZST and not unsized.
pub fn is_zst(&self) -> bool {
match self.abi {
Abi::Uninhabited => true,
Abi::Scalar(_) |
Abi::ScalarPair(..) |
Abi::Vector { .. } => false,
Abi::Aggregate { sized, .. } => sized && self.size.bytes() == 0
Abi::Aggregate { sized } => sized && self.size.bytes() == 0
}
}

Expand Down Expand Up @@ -2452,8 +2412,7 @@ impl<'gcx> HashStable<StableHashingContext<'gcx>> for Abi {
element.hash_stable(hcx, hasher);
count.hash_stable(hcx, hasher);
}
Aggregate { packed, sized } => {
packed.hash_stable(hcx, hasher);
Aggregate { sized } => {
sized.hash_stable(hcx, hasher);
}
}
Expand Down
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