user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Miri: refactor read_discriminant and make it return Scalar

Browse source
This commit is contained in:
Ralf Jung 2020-04-14 12:49:15 +02:00
parent ee6c0dae39
commit 0f18203e85
4 changed files with 86 additions and 70 deletions
Download patch file Download diff file Expand all files Collapse all files

4
src/librustc_middle/mir/interpret/error.rs
View file

@ -1,4 +1,4 @@
use super::{AllocId, Pointer, RawConst, ScalarMaybeUninit};
use super::{AllocId, Pointer, RawConst, Scalar};
use crate::mir::interpret::ConstValue;
use crate::ty::layout::LayoutError;
@ -391,7 +391,7 @@ pub enum UndefinedBehaviorInfo<'tcx> {
/// Using a non-character `u32` as character.
InvalidChar(u32),
/// An enum discriminant was set to a value which was outside the range of valid values.
InvalidDiscriminant(ScalarMaybeUninit),
InvalidDiscriminant(Scalar),
/// Using a pointer-not-to-a-function as function pointer.
InvalidFunctionPointer(Pointer),
/// Using a string that is not valid UTF-8,

10
src/librustc_mir/interpret/intrinsics.rs
View file

@ -218,15 +218,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
sym::discriminant_value => {
let place = self.deref_operand(args[0])?;
let discr_val = self.read_discriminant(place.into())?.0;
let scalar = match dest.layout.ty.kind {
ty::Int(_) => Scalar::from_int(
self.sign_extend(discr_val, dest.layout) as i128,
dest.layout.size,
),
ty::Uint(_) => Scalar::from_uint(discr_val, dest.layout.size),
_ => bug!("invalid `discriminant_value` return layout: {:?}", dest.layout),
};
self.write_scalar(scalar, dest)?;
self.write_scalar(discr_val, dest)?;
}
sym::unchecked_shl
| sym::unchecked_shr

139
src/librustc_mir/interpret/operand.rs
View file

@ -15,8 +15,8 @@ use rustc_target::abi::{Abi, DiscriminantKind, HasDataLayout, Integer, LayoutOf,
use rustc_target::abi::{VariantIdx, Variants};
use super::{
from_known_layout, sign_extend, truncate, ConstValue, GlobalId, InterpCx, InterpResult,
MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit,
from_known_layout, ConstValue, GlobalId, InterpCx, InterpResult, MPlaceTy, Machine, MemPlace,
Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit,
};
/// An `Immediate` represents a single immediate self-contained Rust value.
@ -577,91 +577,112 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
pub fn read_discriminant(
&self,
rval: OpTy<'tcx, M::PointerTag>,
) -> InterpResult<'tcx, (u128, VariantIdx)> {
) -> InterpResult<'tcx, (Scalar<M::PointerTag>, VariantIdx)> {
trace!("read_discriminant_value {:#?}", rval.layout);
let (discr_layout, discr_kind, discr_index) = match rval.layout.variants {
let (discr_scalar_layout, discr_kind, discr_index) = match rval.layout.variants {
Variants::Single { index } => {
let discr_val = rval
.layout
.ty
.discriminant_for_variant(*self.tcx, index)
.map_or(u128::from(index.as_u32()), |discr| discr.val);
return Ok((discr_val, index));
let discr = match rval.layout.ty.discriminant_for_variant(*self.tcx, index) {
Some(discr) => {
// This type actually has discriminants.
let discr_layout = self.layout_of(discr.ty)?;
Scalar::from_uint(discr.val, discr_layout.size)
}
None => {
// On a type without actual discriminants, return variant idx as `u8`.
let discr_layout = self.layout_of(self.tcx.types.u8)?;
Scalar::from_uint(index.as_u32(), discr_layout.size)
}
};
return Ok((discr, index));
}
Variants::Multiple { discr: ref discr_layout, ref discr_kind, discr_index, .. } => {
(discr_layout, discr_kind, discr_index)
Variants::Multiple { ref discr, ref discr_kind, discr_index, .. } => {
(discr, discr_kind, discr_index)
}
};
// read raw discriminant value
let discr_op = self.operand_field(rval, discr_index)?;
let discr_val = self.read_immediate(discr_op)?;
let raw_discr = discr_val.to_scalar_or_undef();
trace!("discr value: {:?}", raw_discr);
// post-process
// There are *three* types/layouts that come into play here:
// - The field storing the discriminant has a layout, which my be a pointer.
// This is `discr_val.layout`; we just use it for sanity checks.
// - The discriminant has a layout for tag storing purposes, which is always an integer.
// This is `discr_layout` and is used to interpret the value we read from the
// discriminant field.
// - The discriminant also has a type for typechecking, and that type's
// layout can be *different*. This is `discr_ty`, and is used for the `Scalar`
// we return. If necessary, a cast from `discr_layout` is performed.
// Get layout for tag.
let discr_layout = self.layout_of(discr_scalar_layout.value.to_int_ty(*self.tcx))?;
// Read discriminant value and sanity-check `discr_layout`.
let discr_val = self.read_immediate(self.operand_field(rval, discr_index)?)?;
assert_eq!(discr_layout.size, discr_val.layout.size);
assert_eq!(discr_layout.abi.is_signed(), discr_val.layout.abi.is_signed());
let discr_val = discr_val.to_scalar()?;
trace!("discriminant value: {:?}", discr_val);
// Get type used by typechecking.
let discr_ty = match rval.layout.ty.kind {
ty::Adt(adt, _) => {
let discr_int_ty = Integer::from_attr(self, adt.repr.discr_type());
// The signedness of tag and discriminant is the same.
discr_int_ty.to_ty(*self.tcx, discr_layout.abi.is_signed())
}
ty::Generator(_, substs, _) => {
let substs = substs.as_generator();
substs.discr_ty(*self.tcx)
}
_ => bug!("multiple variants for non-adt non-generator"),
};
// Figure out which discriminant and variant this corresponds to.
Ok(match *discr_kind {
DiscriminantKind::Tag => {
let bits_discr = raw_discr
.not_undef()
.and_then(|raw_discr| self.force_bits(raw_discr, discr_val.layout.size))
.map_err(|_| err_ub!(InvalidDiscriminant(raw_discr.erase_tag())))?;
let real_discr = if discr_val.layout.abi.is_signed() {
// going from layout tag type to typeck discriminant type
// requires first sign extending with the discriminant layout
let sexted = sign_extend(bits_discr, discr_val.layout.size);
// and then zeroing with the typeck discriminant type
let discr_ty = rval
.layout
.ty
.ty_adt_def()
.expect("tagged layout corresponds to adt")
.repr
.discr_type();
let size = Integer::from_attr(self, discr_ty).size();
truncate(sexted, size)
} else {
bits_discr
};
// Make sure we catch invalid discriminants
let discr_bits = self
.force_bits(discr_val, discr_layout.size)
.map_err(|_| err_ub!(InvalidDiscriminant(discr_val.erase_tag())))?;
// Cast discriminant bits to the right type.
let discr_ty_layout = self.layout_of(discr_ty)?;
let discr_val_cast =
self.cast_from_scalar(discr_bits, discr_layout, discr_ty);
let discr_bits = discr_val_cast.assert_bits(discr_ty_layout.size);
// Find variant index for this tag, and catch invalid discriminants.
let index = match rval.layout.ty.kind {
ty::Adt(adt, _) => {
adt.discriminants(self.tcx.tcx).find(|(_, var)| var.val == real_discr)
adt.discriminants(self.tcx.tcx).find(|(_, var)| var.val == discr_bits)
}
ty::Generator(def_id, substs, _) => {
let substs = substs.as_generator();
substs
.discriminants(def_id, self.tcx.tcx)
.find(|(_, var)| var.val == real_discr)
.find(|(_, var)| var.val == discr_bits)
}
_ => bug!("tagged layout for non-adt non-generator"),
}
.ok_or_else(|| err_ub!(InvalidDiscriminant(raw_discr.erase_tag())))?;
(real_discr, index.0)
.ok_or_else(|| err_ub!(InvalidDiscriminant(discr_val.erase_tag())))?;
// Return the cast value, and the index.
(discr_val_cast, index.0)
}
DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start } => {
// Compute the variant this discriminant corresponds to. With niche layout,
// tag and variant index are the same.
let variants_start = niche_variants.start().as_u32();
let variants_end = niche_variants.end().as_u32();
let raw_discr = raw_discr
.not_undef()
.map_err(|_| err_ub!(InvalidDiscriminant(ScalarMaybeUninit::Uninit)))?;
match raw_discr.to_bits_or_ptr(discr_val.layout.size, self) {
let variant = match discr_val.to_bits_or_ptr(discr_layout.size, self) {
Err(ptr) => {
// The niche must be just 0 (which an inbounds pointer value never is)
let ptr_valid = niche_start == 0
&& variants_start == variants_end
&& !self.memory.ptr_may_be_null(ptr);
if !ptr_valid {
throw_ub!(InvalidDiscriminant(raw_discr.erase_tag().into()))
throw_ub!(InvalidDiscriminant(discr_val.erase_tag()))
}
(u128::from(dataful_variant.as_u32()), dataful_variant)
dataful_variant
}
Ok(raw_discr) => {
Ok(bits_discr) => {
// We need to use machine arithmetic to get the relative variant idx:
// variant_index_relative = discr_val - niche_start_val
let discr_layout =
self.layout_of(discr_layout.value.to_int_ty(*self.tcx))?;
let discr_val = ImmTy::from_uint(raw_discr, discr_layout);
let discr_val = ImmTy::from_uint(bits_discr, discr_layout);
let niche_start_val = ImmTy::from_uint(niche_start, discr_layout);
let variant_index_relative_val =
self.binary_op(mir::BinOp::Sub, discr_val, niche_start_val)?;
@ -684,12 +705,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
.variants
.len();
assert!(usize::try_from(variant_index).unwrap() < variants_len);
(u128::from(variant_index), VariantIdx::from_u32(variant_index))
VariantIdx::from_u32(variant_index)
} else {
(u128::from(dataful_variant.as_u32()), dataful_variant)
dataful_variant
}
}
}
};
// Compute the size of the scalar we need to return.
// FIXME: Why do we not need to do a cast here like we do above?
let size = self.layout_of(discr_ty)?.size;
(Scalar::from_uint(variant.as_u32(), size), variant)
}
})
}

3
src/librustc_mir/interpret/step.rs
View file

@ -262,8 +262,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Discriminant(place) => {
let op = self.eval_place_to_op(place, None)?;
let discr_val = self.read_discriminant(op)?.0;
let size = dest.layout.size;
self.write_scalar(Scalar::from_uint(discr_val, size), dest)?;
self.write_scalar(discr_val, dest)?;
}
}