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Weave the alignment through `ByRef`

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oli-obk committed Jun 14, 2019
1 parent 921f0d9 commit fb37bf0037833026c3ffe6ec1fe3367fec5a5e0e
@@ -2,7 +2,7 @@ use std::fmt;
use rustc_macros::HashStable;
use rustc_apfloat::{Float, ieee::{Double, Single}};

use crate::ty::{Ty, InferConst, ParamConst, layout::{HasDataLayout, Size}, subst::SubstsRef};
use crate::ty::{Ty, InferConst, ParamConst, layout::{HasDataLayout, Size, Align}, subst::SubstsRef};
use crate::ty::PlaceholderConst;
use crate::hir::def_id::DefId;

@@ -45,7 +45,9 @@ pub enum ConstValue<'tcx> {

/// An allocation together with a pointer into the allocation.
/// Invariant: the pointer's `AllocId` resolves to the allocation.
ByRef(Pointer, &'tcx Allocation),
/// The alignment exists to allow `const_field` to have `ByRef` access to nonprimitive fields
/// of packed structs.
ByRef(Pointer, Align, &'tcx Allocation),

/// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
/// variants when the code is monomorphic enough for that.
@@ -1335,7 +1335,7 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
impl<'tcx> TypeFoldable<'tcx> for ConstValue<'tcx> {
fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
match *self {
ConstValue::ByRef(ptr, alloc) => ConstValue::ByRef(ptr, alloc),
ConstValue::ByRef(ptr, align, alloc) => ConstValue::ByRef(ptr, align, alloc),
ConstValue::Infer(ic) => ConstValue::Infer(ic.fold_with(folder)),
ConstValue::Param(p) => ConstValue::Param(p.fold_with(folder)),
ConstValue::Placeholder(p) => ConstValue::Placeholder(p),
@@ -11,7 +11,7 @@ use crate::value::Value;
use rustc_codegen_ssa::traits::*;

use crate::consts::const_alloc_to_llvm;
use rustc::ty::layout::{HasDataLayout, LayoutOf, self, TyLayout, Size};
use rustc::ty::layout::{HasDataLayout, LayoutOf, self, TyLayout, Size, Align};
use rustc::mir::interpret::{Scalar, GlobalAlloc, Allocation};
use rustc_codegen_ssa::mir::place::PlaceRef;

@@ -344,19 +344,20 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
fn from_const_alloc(
&self,
layout: TyLayout<'tcx>,
align: Align,
alloc: &Allocation,
offset: Size,
) -> PlaceRef<'tcx, &'ll Value> {
let init = const_alloc_to_llvm(self, alloc);
let base_addr = self.static_addr_of(init, layout.align.abi, None);
let base_addr = self.static_addr_of(init, align, None);

let llval = unsafe { llvm::LLVMConstInBoundsGEP(
self.const_bitcast(base_addr, self.type_i8p()),
&self.const_usize(offset.bytes()),
1,
)};
let llval = self.const_bitcast(llval, self.type_ptr_to(layout.llvm_type(self)));
PlaceRef::new_sized(llval, layout, alloc.align)
PlaceRef::new_sized(llval, layout, align)
}

fn const_ptrcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
@@ -71,7 +71,9 @@ pub fn codegen_static_initializer(
let static_ = cx.tcx.const_eval(param_env.and(cid))?;

let alloc = match static_.val {
ConstValue::ByRef(ptr, alloc) if ptr.offset.bytes() == 0 => alloc,
ConstValue::ByRef(ptr, align, alloc) if ptr.offset.bytes() == 0 && align == alloc.align => {
alloc
},
_ => bug!("static const eval returned {:#?}", static_),
};
Ok((const_alloc_to_llvm(cx, alloc), alloc))
@@ -109,8 +109,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
let b_llval = bx.const_usize((end - start) as u64);
OperandValue::Pair(a_llval, b_llval)
},
ConstValue::ByRef(ptr, alloc) => {
return bx.load_operand(bx.from_const_alloc(layout, alloc, ptr.offset));
ConstValue::ByRef(ptr, align, alloc) => {
return bx.load_operand(bx.from_const_alloc(layout, align, alloc, ptr.offset));
},
};

@@ -424,8 +424,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let layout = cx.layout_of(self.monomorphize(&ty));
match bx.tcx().const_eval(param_env.and(cid)) {
Ok(val) => match val.val {
mir::interpret::ConstValue::ByRef(ptr, alloc) => {
bx.cx().from_const_alloc(layout, alloc, ptr.offset)
mir::interpret::ConstValue::ByRef(ptr, align, alloc) => {
bx.cx().from_const_alloc(layout, align, alloc, ptr.offset)
}
_ => bug!("promoteds should have an allocation: {:?}", val),
},
@@ -34,6 +34,7 @@ pub trait ConstMethods<'tcx>: BackendTypes {
fn from_const_alloc(
&self,
layout: layout::TyLayout<'tcx>,
align: layout::Align,
alloc: &Allocation,
offset: layout::Size,
) -> PlaceRef<'tcx, Self::Value>;
@@ -99,7 +99,7 @@ fn op_to_const<'tcx>(
Ok(mplace) => {
let ptr = mplace.ptr.to_ptr().unwrap();
let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
ConstValue::ByRef(ptr, alloc)
ConstValue::ByRef(ptr, mplace.align, alloc)
},
// see comment on `let try_as_immediate` above
Err(ImmTy { imm: Immediate::Scalar(x), .. }) => match x {
@@ -113,7 +113,7 @@ fn op_to_const<'tcx>(
let mplace = op.to_mem_place();
let ptr = mplace.ptr.to_ptr().unwrap();
let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
ConstValue::ByRef(ptr, alloc)
ConstValue::ByRef(ptr, mplace.align, alloc)
},
},
Err(ImmTy { imm: Immediate::ScalarPair(a, b), .. }) => {
@@ -482,10 +482,7 @@ pub fn const_field<'tcx>(
trace!("const_field: {:?}, {:?}", field, value);
let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env);
// get the operand again
let mut op = ecx.eval_const_to_op(value, None).unwrap();
// Ignore the alignment when accessing the field, since it may be a field of a
// packed struct and thus end up causing an alignment error if we read from it.
op.force_unaligned_access();
let op = ecx.eval_const_to_op(value, None).unwrap();
// downcast
let down = match variant {
None => op,
@@ -544,7 +541,11 @@ fn validate_and_turn_into_const<'tcx>(
if tcx.is_static(def_id) || cid.promoted.is_some() {
let ptr = mplace.ptr.to_ptr()?;
Ok(tcx.mk_const(ty::Const {
val: ConstValue::ByRef(ptr, ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id)),
val: ConstValue::ByRef(
ptr,
mplace.align,
ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id),
),
ty: mplace.layout.ty,
}))
} else {
@@ -215,10 +215,15 @@ impl LiteralExpander<'tcx> {
debug!("fold_const_value_deref {:?} {:?} {:?}", val, rty, crty);
match (val, &crty.sty, &rty.sty) {
// the easy case, deref a reference
(ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => ConstValue::ByRef(
p,
self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id),
),
(ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => {
let alloc = self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id);
ConstValue::ByRef(
p,
// FIXME(oli-obk): this should be the type's layout
alloc.align,
alloc,
)
},
// unsize array to slice if pattern is array but match value or other patterns are slice
(ConstValue::Scalar(Scalar::Ptr(p)), ty::Array(t, n), ty::Slice(u)) => {
assert_eq!(t, u);
@@ -1431,7 +1436,7 @@ fn slice_pat_covered_by_const<'tcx>(
suffix: &[Pattern<'tcx>],
) -> Result<bool, ErrorReported> {
let data: &[u8] = match (const_val.val, &const_val.ty.sty) {
(ConstValue::ByRef(ptr, alloc), ty::Array(t, n)) => {
(ConstValue::ByRef(ptr, _, alloc), ty::Array(t, n)) => {
assert_eq!(*t, tcx.types.u8);
let n = n.assert_usize(tcx).unwrap();
alloc.get_bytes(&tcx, ptr, Size::from_bytes(n)).unwrap()
@@ -1753,7 +1758,7 @@ fn specialize<'p, 'a: 'p, 'tcx>(
let (alloc, offset, n, ty) = match value.ty.sty {
ty::Array(t, n) => {
match value.val {
ConstValue::ByRef(ptr, alloc) => (
ConstValue::ByRef(ptr, _, alloc) => (
alloc,
ptr.offset,
n.unwrap_usize(cx.tcx),
@@ -5,7 +5,7 @@ use std::convert::TryInto;

use rustc::{mir, ty};
use rustc::ty::layout::{
self, Size, LayoutOf, TyLayout, HasDataLayout, IntegerExt, VariantIdx, Align,
self, Size, LayoutOf, TyLayout, HasDataLayout, IntegerExt, VariantIdx,
};

use rustc::mir::interpret::{
@@ -179,19 +179,6 @@ impl<'tcx, Tag> From<ImmTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
}
}

impl<'tcx, Tag> OpTy<'tcx, Tag> {
/// This function exists solely for pattern matching. If we pattern match a packed struct with
/// an ADT field, the constant representing that field will have lost the information about the
/// packedness. We could clone the allocation and adjust the alignment, but that seems wasteful,
/// since the alignment is already encoded in the allocation. We know it is alright, because
/// validation checked everything before the initial constant entered match checking.
pub(crate) fn force_unaligned_access(&mut self) {
if let Operand::Indirect(mplace) = &mut self.op {
mplace.align = Align::from_bytes(1).unwrap();
}
}
}

impl<'tcx, Tag: Copy> ImmTy<'tcx, Tag>
{
#[inline]
@@ -551,11 +538,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpretCx<'mir, 'tcx, M> {
self.layout_of(self.monomorphize(val.ty)?)
})?;
let op = match val.val {
ConstValue::ByRef(ptr, _alloc) => {
ConstValue::ByRef(ptr, align, _alloc) => {
// We rely on mutability being set correctly in that allocation to prevent writes
// where none should happen.
let ptr = self.tag_static_base_pointer(ptr);
Operand::Indirect(MemPlace::from_ptr(ptr, layout.align.abi))
Operand::Indirect(MemPlace::from_ptr(ptr, align))
},
ConstValue::Scalar(x) =>
Operand::Immediate(Immediate::Scalar(tag_scalar(x).into())),
@@ -1262,7 +1262,7 @@ fn collect_const<'tcx>(
ConstValue::Scalar(Scalar::Ptr(ptr)) =>
collect_miri(tcx, ptr.alloc_id, output),
ConstValue::Slice { data: alloc, start: _, end: _ } |
ConstValue::ByRef(_, alloc) => {
ConstValue::ByRef(_, _, alloc) => {
for &((), id) in alloc.relocations.values() {
collect_miri(tcx, id, output);
}
@@ -1448,7 +1448,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span)
};
let param_env = ty::ParamEnv::reveal_all();
if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
let alloc = if let ConstValue::ByRef(_, allocation) = static_.val {
let alloc = if let ConstValue::ByRef(_, _, allocation) = static_.val {
allocation
} else {
bug!("Matching on non-ByRef static")

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