Rename rustc_mir to rustc_const_eval.
This commit is contained in:
Camille GILLOT
762
compiler/rustc_const_eval/src/interpret/operand.rs
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762
compiler/rustc_const_eval/src/interpret/operand.rs
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@@ -0,0 +1,762 @@
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//! Functions concerning immediate values and operands, and reading from operands.
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//! All high-level functions to read from memory work on operands as sources.
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use std::convert::TryFrom;
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use std::fmt::Write;
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use rustc_errors::ErrorReported;
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use rustc_hir::def::Namespace;
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use rustc_macros::HashStable;
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use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout};
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use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Printer};
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use rustc_middle::ty::{ConstInt, Ty};
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use rustc_middle::{mir, ty};
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use rustc_target::abi::{Abi, HasDataLayout, Size, TagEncoding};
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use rustc_target::abi::{VariantIdx, Variants};
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use super::{
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alloc_range, from_known_layout, mir_assign_valid_types, AllocId, ConstValue, GlobalId,
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InterpCx, InterpResult, MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Provenance,
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Scalar, ScalarMaybeUninit,
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};
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/// An `Immediate` represents a single immediate self-contained Rust value.
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///
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/// For optimization of a few very common cases, there is also a representation for a pair of
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/// primitive values (`ScalarPair`). It allows Miri to avoid making allocations for checked binary
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/// operations and wide pointers. This idea was taken from rustc's codegen.
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/// In particular, thanks to `ScalarPair`, arithmetic operations and casts can be entirely
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/// defined on `Immediate`, and do not have to work with a `Place`.
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#[derive(Copy, Clone, PartialEq, Eq, HashStable, Hash, Debug)]
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pub enum Immediate<Tag: Provenance = AllocId> {
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Scalar(ScalarMaybeUninit<Tag>),
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ScalarPair(ScalarMaybeUninit<Tag>, ScalarMaybeUninit<Tag>),
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}
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#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
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rustc_data_structures::static_assert_size!(Immediate, 56);
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impl<Tag: Provenance> From<ScalarMaybeUninit<Tag>> for Immediate<Tag> {
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#[inline(always)]
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fn from(val: ScalarMaybeUninit<Tag>) -> Self {
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Immediate::Scalar(val)
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}
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}
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impl<Tag: Provenance> From<Scalar<Tag>> for Immediate<Tag> {
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#[inline(always)]
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fn from(val: Scalar<Tag>) -> Self {
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Immediate::Scalar(val.into())
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}
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}
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impl<'tcx, Tag: Provenance> Immediate<Tag> {
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pub fn from_pointer(p: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
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Immediate::Scalar(ScalarMaybeUninit::from_pointer(p, cx))
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}
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pub fn from_maybe_pointer(p: Pointer<Option<Tag>>, cx: &impl HasDataLayout) -> Self {
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Immediate::Scalar(ScalarMaybeUninit::from_maybe_pointer(p, cx))
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}
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pub fn new_slice(val: Scalar<Tag>, len: u64, cx: &impl HasDataLayout) -> Self {
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Immediate::ScalarPair(val.into(), Scalar::from_machine_usize(len, cx).into())
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}
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pub fn new_dyn_trait(
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val: Scalar<Tag>,
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vtable: Pointer<Option<Tag>>,
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cx: &impl HasDataLayout,
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) -> Self {
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Immediate::ScalarPair(val.into(), ScalarMaybeUninit::from_maybe_pointer(vtable, cx))
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}
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#[inline]
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pub fn to_scalar_or_uninit(self) -> ScalarMaybeUninit<Tag> {
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match self {
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Immediate::Scalar(val) => val,
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Immediate::ScalarPair(..) => bug!("Got a scalar pair where a scalar was expected"),
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}
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}
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#[inline]
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pub fn to_scalar(self) -> InterpResult<'tcx, Scalar<Tag>> {
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self.to_scalar_or_uninit().check_init()
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}
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#[inline]
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pub fn to_scalar_pair(self) -> InterpResult<'tcx, (Scalar<Tag>, Scalar<Tag>)> {
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match self {
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Immediate::ScalarPair(val1, val2) => Ok((val1.check_init()?, val2.check_init()?)),
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Immediate::Scalar(..) => {
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bug!("Got a scalar where a scalar pair was expected")
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}
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}
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}
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}
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// ScalarPair needs a type to interpret, so we often have an immediate and a type together
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// as input for binary and cast operations.
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#[derive(Copy, Clone, Debug)]
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pub struct ImmTy<'tcx, Tag: Provenance = AllocId> {
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imm: Immediate<Tag>,
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pub layout: TyAndLayout<'tcx>,
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}
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#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
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rustc_data_structures::static_assert_size!(ImmTy<'_>, 72);
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impl<Tag: Provenance> std::fmt::Display for ImmTy<'tcx, Tag> {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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/// Helper function for printing a scalar to a FmtPrinter
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fn p<'a, 'tcx, F: std::fmt::Write, Tag: Provenance>(
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cx: FmtPrinter<'a, 'tcx, F>,
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s: ScalarMaybeUninit<Tag>,
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ty: Ty<'tcx>,
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) -> Result<FmtPrinter<'a, 'tcx, F>, std::fmt::Error> {
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match s {
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ScalarMaybeUninit::Scalar(Scalar::Int(int)) => {
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cx.pretty_print_const_scalar_int(int, ty, true)
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}
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ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr, _sz)) => {
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// Just print the ptr value. `pretty_print_const_scalar_ptr` would also try to
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// print what is points to, which would fail since it has no access to the local
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// memory.
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cx.pretty_print_const_pointer(ptr, ty, true)
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}
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ScalarMaybeUninit::Uninit => cx.typed_value(
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|mut this| {
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this.write_str("uninit ")?;
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Ok(this)
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},
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|this| this.print_type(ty),
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" ",
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),
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}
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}
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ty::tls::with(|tcx| {
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match self.imm {
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Immediate::Scalar(s) => {
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if let Some(ty) = tcx.lift(self.layout.ty) {
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let cx = FmtPrinter::new(tcx, f, Namespace::ValueNS);
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p(cx, s, ty)?;
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return Ok(());
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}
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write!(f, "{}: {}", s, self.layout.ty)
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}
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Immediate::ScalarPair(a, b) => {
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// FIXME(oli-obk): at least print tuples and slices nicely
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write!(f, "({}, {}): {}", a, b, self.layout.ty,)
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}
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}
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})
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}
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}
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impl<'tcx, Tag: Provenance> std::ops::Deref for ImmTy<'tcx, Tag> {
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type Target = Immediate<Tag>;
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#[inline(always)]
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fn deref(&self) -> &Immediate<Tag> {
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&self.imm
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}
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}
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/// An `Operand` is the result of computing a `mir::Operand`. It can be immediate,
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/// or still in memory. The latter is an optimization, to delay reading that chunk of
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/// memory and to avoid having to store arbitrary-sized data here.
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#[derive(Copy, Clone, PartialEq, Eq, HashStable, Hash, Debug)]
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pub enum Operand<Tag: Provenance = AllocId> {
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Immediate(Immediate<Tag>),
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Indirect(MemPlace<Tag>),
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}
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub struct OpTy<'tcx, Tag: Provenance = AllocId> {
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op: Operand<Tag>, // Keep this private; it helps enforce invariants.
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pub layout: TyAndLayout<'tcx>,
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}
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#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
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rustc_data_structures::static_assert_size!(OpTy<'_>, 80);
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impl<'tcx, Tag: Provenance> std::ops::Deref for OpTy<'tcx, Tag> {
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type Target = Operand<Tag>;
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#[inline(always)]
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fn deref(&self) -> &Operand<Tag> {
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&self.op
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}
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}
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impl<'tcx, Tag: Provenance> From<MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
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#[inline(always)]
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fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
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OpTy { op: Operand::Indirect(*mplace), layout: mplace.layout }
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}
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}
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impl<'tcx, Tag: Provenance> From<&'_ MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
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#[inline(always)]
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fn from(mplace: &MPlaceTy<'tcx, Tag>) -> Self {
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OpTy { op: Operand::Indirect(**mplace), layout: mplace.layout }
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}
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}
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impl<'tcx, Tag: Provenance> From<ImmTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
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#[inline(always)]
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fn from(val: ImmTy<'tcx, Tag>) -> Self {
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OpTy { op: Operand::Immediate(val.imm), layout: val.layout }
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}
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}
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impl<'tcx, Tag: Provenance> ImmTy<'tcx, Tag> {
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#[inline]
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pub fn from_scalar(val: Scalar<Tag>, layout: TyAndLayout<'tcx>) -> Self {
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ImmTy { imm: val.into(), layout }
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}
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#[inline]
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pub fn from_immediate(imm: Immediate<Tag>, layout: TyAndLayout<'tcx>) -> Self {
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ImmTy { imm, layout }
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}
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#[inline]
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pub fn try_from_uint(i: impl Into<u128>, layout: TyAndLayout<'tcx>) -> Option<Self> {
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Some(Self::from_scalar(Scalar::try_from_uint(i, layout.size)?, layout))
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}
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#[inline]
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pub fn from_uint(i: impl Into<u128>, layout: TyAndLayout<'tcx>) -> Self {
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Self::from_scalar(Scalar::from_uint(i, layout.size), layout)
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}
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#[inline]
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pub fn try_from_int(i: impl Into<i128>, layout: TyAndLayout<'tcx>) -> Option<Self> {
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Some(Self::from_scalar(Scalar::try_from_int(i, layout.size)?, layout))
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}
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#[inline]
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pub fn from_int(i: impl Into<i128>, layout: TyAndLayout<'tcx>) -> Self {
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Self::from_scalar(Scalar::from_int(i, layout.size), layout)
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}
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#[inline]
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pub fn to_const_int(self) -> ConstInt {
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assert!(self.layout.ty.is_integral());
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let int = self.to_scalar().expect("to_const_int doesn't work on scalar pairs").assert_int();
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ConstInt::new(int, self.layout.ty.is_signed(), self.layout.ty.is_ptr_sized_integral())
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}
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}
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impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
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/// Try reading an immediate in memory; this is interesting particularly for `ScalarPair`.
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/// Returns `None` if the layout does not permit loading this as a value.
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fn try_read_immediate_from_mplace(
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&self,
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mplace: &MPlaceTy<'tcx, M::PointerTag>,
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) -> InterpResult<'tcx, Option<ImmTy<'tcx, M::PointerTag>>> {
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if mplace.layout.is_unsized() {
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// Don't touch unsized
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return Ok(None);
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}
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let alloc = match self.get_alloc(mplace)? {
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Some(ptr) => ptr,
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None => {
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return Ok(Some(ImmTy {
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// zero-sized type
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imm: Scalar::ZST.into(),
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layout: mplace.layout,
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}));
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}
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};
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match mplace.layout.abi {
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Abi::Scalar(..) => {
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let scalar = alloc.read_scalar(alloc_range(Size::ZERO, mplace.layout.size))?;
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Ok(Some(ImmTy { imm: scalar.into(), layout: mplace.layout }))
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}
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Abi::ScalarPair(ref a, ref b) => {
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// We checked `ptr_align` above, so all fields will have the alignment they need.
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// We would anyway check against `ptr_align.restrict_for_offset(b_offset)`,
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// which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
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let (a, b) = (&a.value, &b.value);
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let (a_size, b_size) = (a.size(self), b.size(self));
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let b_offset = a_size.align_to(b.align(self).abi);
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assert!(b_offset.bytes() > 0); // we later use the offset to tell apart the fields
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let a_val = alloc.read_scalar(alloc_range(Size::ZERO, a_size))?;
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let b_val = alloc.read_scalar(alloc_range(b_offset, b_size))?;
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Ok(Some(ImmTy { imm: Immediate::ScalarPair(a_val, b_val), layout: mplace.layout }))
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}
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_ => Ok(None),
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}
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}
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/// Try returning an immediate for the operand.
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/// If the layout does not permit loading this as an immediate, return where in memory
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/// we can find the data.
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/// Note that for a given layout, this operation will either always fail or always
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/// succeed! Whether it succeeds depends on whether the layout can be represented
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/// in an `Immediate`, not on which data is stored there currently.
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pub fn try_read_immediate(
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&self,
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src: &OpTy<'tcx, M::PointerTag>,
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) -> InterpResult<'tcx, Result<ImmTy<'tcx, M::PointerTag>, MPlaceTy<'tcx, M::PointerTag>>> {
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Ok(match src.try_as_mplace() {
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Ok(ref mplace) => {
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if let Some(val) = self.try_read_immediate_from_mplace(mplace)? {
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Ok(val)
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} else {
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Err(*mplace)
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}
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}
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Err(val) => Ok(val),
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})
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}
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/// Read an immediate from a place, asserting that that is possible with the given layout.
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#[inline(always)]
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pub fn read_immediate(
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&self,
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op: &OpTy<'tcx, M::PointerTag>,
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) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
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if let Ok(imm) = self.try_read_immediate(op)? {
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Ok(imm)
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} else {
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span_bug!(self.cur_span(), "primitive read failed for type: {:?}", op.layout.ty);
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}
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}
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/// Read a scalar from a place
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pub fn read_scalar(
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&self,
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op: &OpTy<'tcx, M::PointerTag>,
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) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>> {
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Ok(self.read_immediate(op)?.to_scalar_or_uninit())
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}
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/// Read a pointer from a place.
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pub fn read_pointer(
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&self,
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op: &OpTy<'tcx, M::PointerTag>,
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) -> InterpResult<'tcx, Pointer<Option<M::PointerTag>>> {
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Ok(self.scalar_to_ptr(self.read_scalar(op)?.check_init()?))
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}
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// Turn the wide MPlace into a string (must already be dereferenced!)
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pub fn read_str(&self, mplace: &MPlaceTy<'tcx, M::PointerTag>) -> InterpResult<'tcx, &str> {
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let len = mplace.len(self)?;
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let bytes = self.memory.read_bytes(mplace.ptr, Size::from_bytes(len))?;
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let str = std::str::from_utf8(bytes).map_err(|err| err_ub!(InvalidStr(err)))?;
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Ok(str)
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}
|
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/// Projection functions
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pub fn operand_field(
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&self,
|
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op: &OpTy<'tcx, M::PointerTag>,
|
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field: usize,
|
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) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
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let base = match op.try_as_mplace() {
|
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Ok(ref mplace) => {
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// We can reuse the mplace field computation logic for indirect operands.
|
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let field = self.mplace_field(mplace, field)?;
|
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return Ok(field.into());
|
||||
}
|
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Err(value) => value,
|
||||
};
|
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|
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let field_layout = op.layout.field(self, field);
|
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if field_layout.is_zst() {
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let immediate = Scalar::ZST.into();
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return Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout });
|
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}
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let offset = op.layout.fields.offset(field);
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let immediate = match *base {
|
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// the field covers the entire type
|
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_ if offset.bytes() == 0 && field_layout.size == op.layout.size => *base,
|
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// extract fields from types with `ScalarPair` ABI
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Immediate::ScalarPair(a, b) => {
|
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let val = if offset.bytes() == 0 { a } else { b };
|
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Immediate::from(val)
|
||||
}
|
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Immediate::Scalar(val) => span_bug!(
|
||||
self.cur_span(),
|
||||
"field access on non aggregate {:#?}, {:#?}",
|
||||
val,
|
||||
op.layout
|
||||
),
|
||||
};
|
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Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout })
|
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}
|
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|
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pub fn operand_index(
|
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&self,
|
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op: &OpTy<'tcx, M::PointerTag>,
|
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index: u64,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
if let Ok(index) = usize::try_from(index) {
|
||||
// We can just treat this as a field.
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self.operand_field(op, index)
|
||||
} else {
|
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// Indexing into a big array. This must be an mplace.
|
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let mplace = op.assert_mem_place();
|
||||
Ok(self.mplace_index(&mplace, index)?.into())
|
||||
}
|
||||
}
|
||||
|
||||
pub fn operand_downcast(
|
||||
&self,
|
||||
op: &OpTy<'tcx, M::PointerTag>,
|
||||
variant: VariantIdx,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
// Downcasts only change the layout
|
||||
Ok(match op.try_as_mplace() {
|
||||
Ok(ref mplace) => self.mplace_downcast(mplace, variant)?.into(),
|
||||
Err(..) => {
|
||||
let layout = op.layout.for_variant(self, variant);
|
||||
OpTy { layout, ..*op }
|
||||
}
|
||||
})
|
||||
}
|
||||
|
||||
pub fn operand_projection(
|
||||
&self,
|
||||
base: &OpTy<'tcx, M::PointerTag>,
|
||||
proj_elem: mir::PlaceElem<'tcx>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
use rustc_middle::mir::ProjectionElem::*;
|
||||
Ok(match proj_elem {
|
||||
Field(field, _) => self.operand_field(base, field.index())?,
|
||||
Downcast(_, variant) => self.operand_downcast(base, variant)?,
|
||||
Deref => self.deref_operand(base)?.into(),
|
||||
Subslice { .. } | ConstantIndex { .. } | Index(_) => {
|
||||
// The rest should only occur as mplace, we do not use Immediates for types
|
||||
// allowing such operations. This matches place_projection forcing an allocation.
|
||||
let mplace = base.assert_mem_place();
|
||||
self.mplace_projection(&mplace, proj_elem)?.into()
|
||||
}
|
||||
})
|
||||
}
|
||||
|
||||
/// Read from a local. Will not actually access the local if reading from a ZST.
|
||||
/// Will not access memory, instead an indirect `Operand` is returned.
|
||||
///
|
||||
/// This is public because it is used by [priroda](https://github.com/oli-obk/priroda) to get an
|
||||
/// OpTy from a local
|
||||
pub fn access_local(
|
||||
&self,
|
||||
frame: &super::Frame<'mir, 'tcx, M::PointerTag, M::FrameExtra>,
|
||||
local: mir::Local,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
let layout = self.layout_of_local(frame, local, layout)?;
|
||||
let op = if layout.is_zst() {
|
||||
// Do not read from ZST, they might not be initialized
|
||||
Operand::Immediate(Scalar::ZST.into())
|
||||
} else {
|
||||
M::access_local(&self, frame, local)?
|
||||
};
|
||||
Ok(OpTy { op, layout })
|
||||
}
|
||||
|
||||
/// Every place can be read from, so we can turn them into an operand.
|
||||
/// This will definitely return `Indirect` if the place is a `Ptr`, i.e., this
|
||||
/// will never actually read from memory.
|
||||
#[inline(always)]
|
||||
pub fn place_to_op(
|
||||
&self,
|
||||
place: &PlaceTy<'tcx, M::PointerTag>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
let op = match **place {
|
||||
Place::Ptr(mplace) => Operand::Indirect(mplace),
|
||||
Place::Local { frame, local } => {
|
||||
*self.access_local(&self.stack()[frame], local, None)?
|
||||
}
|
||||
};
|
||||
Ok(OpTy { op, layout: place.layout })
|
||||
}
|
||||
|
||||
// Evaluate a place with the goal of reading from it. This lets us sometimes
|
||||
// avoid allocations.
|
||||
pub fn eval_place_to_op(
|
||||
&self,
|
||||
place: mir::Place<'tcx>,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
// Do not use the layout passed in as argument if the base we are looking at
|
||||
// here is not the entire place.
|
||||
let layout = if place.projection.is_empty() { layout } else { None };
|
||||
|
||||
let base_op = self.access_local(self.frame(), place.local, layout)?;
|
||||
|
||||
let op = place
|
||||
.projection
|
||||
.iter()
|
||||
.try_fold(base_op, |op, elem| self.operand_projection(&op, elem))?;
|
||||
|
||||
trace!("eval_place_to_op: got {:?}", *op);
|
||||
// Sanity-check the type we ended up with.
|
||||
debug_assert!(mir_assign_valid_types(
|
||||
*self.tcx,
|
||||
self.param_env,
|
||||
self.layout_of(self.subst_from_current_frame_and_normalize_erasing_regions(
|
||||
place.ty(&self.frame().body.local_decls, *self.tcx).ty
|
||||
))?,
|
||||
op.layout,
|
||||
));
|
||||
Ok(op)
|
||||
}
|
||||
|
||||
/// Evaluate the operand, returning a place where you can then find the data.
|
||||
/// If you already know the layout, you can save two table lookups
|
||||
/// by passing it in here.
|
||||
#[inline]
|
||||
pub fn eval_operand(
|
||||
&self,
|
||||
mir_op: &mir::Operand<'tcx>,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
use rustc_middle::mir::Operand::*;
|
||||
let op = match *mir_op {
|
||||
// FIXME: do some more logic on `move` to invalidate the old location
|
||||
Copy(place) | Move(place) => self.eval_place_to_op(place, layout)?,
|
||||
|
||||
Constant(ref constant) => {
|
||||
let val =
|
||||
self.subst_from_current_frame_and_normalize_erasing_regions(constant.literal);
|
||||
// This can still fail:
|
||||
// * During ConstProp, with `TooGeneric` or since the `requried_consts` were not all
|
||||
// checked yet.
|
||||
// * During CTFE, since promoteds in `const`/`static` initializer bodies can fail.
|
||||
|
||||
self.mir_const_to_op(&val, layout)?
|
||||
}
|
||||
};
|
||||
trace!("{:?}: {:?}", mir_op, *op);
|
||||
Ok(op)
|
||||
}
|
||||
|
||||
/// Evaluate a bunch of operands at once
|
||||
pub(super) fn eval_operands(
|
||||
&self,
|
||||
ops: &[mir::Operand<'tcx>],
|
||||
) -> InterpResult<'tcx, Vec<OpTy<'tcx, M::PointerTag>>> {
|
||||
ops.iter().map(|op| self.eval_operand(op, None)).collect()
|
||||
}
|
||||
|
||||
// Used when the miri-engine runs into a constant and for extracting information from constants
|
||||
// in patterns via the `const_eval` module
|
||||
/// The `val` and `layout` are assumed to already be in our interpreter
|
||||
/// "universe" (param_env).
|
||||
pub fn const_to_op(
|
||||
&self,
|
||||
val: &ty::Const<'tcx>,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
match val.val {
|
||||
ty::ConstKind::Param(_) | ty::ConstKind::Bound(..) => throw_inval!(TooGeneric),
|
||||
ty::ConstKind::Error(_) => throw_inval!(AlreadyReported(ErrorReported)),
|
||||
ty::ConstKind::Unevaluated(uv) => {
|
||||
let instance = self.resolve(uv.def, uv.substs(*self.tcx))?;
|
||||
Ok(self.eval_to_allocation(GlobalId { instance, promoted: uv.promoted })?.into())
|
||||
}
|
||||
ty::ConstKind::Infer(..) | ty::ConstKind::Placeholder(..) => {
|
||||
span_bug!(self.cur_span(), "const_to_op: Unexpected ConstKind {:?}", val)
|
||||
}
|
||||
ty::ConstKind::Value(val_val) => self.const_val_to_op(val_val, val.ty, layout),
|
||||
}
|
||||
}
|
||||
|
||||
pub fn mir_const_to_op(
|
||||
&self,
|
||||
val: &mir::ConstantKind<'tcx>,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
match val {
|
||||
mir::ConstantKind::Ty(ct) => self.const_to_op(ct, layout),
|
||||
mir::ConstantKind::Val(val, ty) => self.const_val_to_op(*val, ty, layout),
|
||||
}
|
||||
}
|
||||
|
||||
crate fn const_val_to_op(
|
||||
&self,
|
||||
val_val: ConstValue<'tcx>,
|
||||
ty: Ty<'tcx>,
|
||||
layout: Option<TyAndLayout<'tcx>>,
|
||||
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
|
||||
// Other cases need layout.
|
||||
let tag_scalar = |scalar| -> InterpResult<'tcx, _> {
|
||||
Ok(match scalar {
|
||||
Scalar::Ptr(ptr, size) => Scalar::Ptr(self.global_base_pointer(ptr)?, size),
|
||||
Scalar::Int(int) => Scalar::Int(int),
|
||||
})
|
||||
};
|
||||
let layout = from_known_layout(self.tcx, self.param_env, layout, || self.layout_of(ty))?;
|
||||
let op = match val_val {
|
||||
ConstValue::ByRef { alloc, offset } => {
|
||||
let id = self.tcx.create_memory_alloc(alloc);
|
||||
// We rely on mutability being set correctly in that allocation to prevent writes
|
||||
// where none should happen.
|
||||
let ptr = self.global_base_pointer(Pointer::new(id, offset))?;
|
||||
Operand::Indirect(MemPlace::from_ptr(ptr.into(), layout.align.abi))
|
||||
}
|
||||
ConstValue::Scalar(x) => Operand::Immediate(tag_scalar(x)?.into()),
|
||||
ConstValue::Slice { data, start, end } => {
|
||||
// We rely on mutability being set correctly in `data` to prevent writes
|
||||
// where none should happen.
|
||||
let ptr = Pointer::new(
|
||||
self.tcx.create_memory_alloc(data),
|
||||
Size::from_bytes(start), // offset: `start`
|
||||
);
|
||||
Operand::Immediate(Immediate::new_slice(
|
||||
Scalar::from_pointer(self.global_base_pointer(ptr)?, &*self.tcx),
|
||||
u64::try_from(end.checked_sub(start).unwrap()).unwrap(), // len: `end - start`
|
||||
self,
|
||||
))
|
||||
}
|
||||
};
|
||||
Ok(OpTy { op, layout })
|
||||
}
|
||||
|
||||
/// Read discriminant, return the runtime value as well as the variant index.
|
||||
pub fn read_discriminant(
|
||||
&self,
|
||||
op: &OpTy<'tcx, M::PointerTag>,
|
||||
) -> InterpResult<'tcx, (Scalar<M::PointerTag>, VariantIdx)> {
|
||||
trace!("read_discriminant_value {:#?}", op.layout);
|
||||
// Get type and layout of the discriminant.
|
||||
let discr_layout = self.layout_of(op.layout.ty.discriminant_ty(*self.tcx))?;
|
||||
trace!("discriminant type: {:?}", discr_layout.ty);
|
||||
|
||||
// We use "discriminant" to refer to the value associated with a particular enum variant.
|
||||
// This is not to be confused with its "variant index", which is just determining its position in the
|
||||
// declared list of variants -- they can differ with explicitly assigned discriminants.
|
||||
// We use "tag" to refer to how the discriminant is encoded in memory, which can be either
|
||||
// straight-forward (`TagEncoding::Direct`) or with a niche (`TagEncoding::Niche`).
|
||||
let (tag_scalar_layout, tag_encoding, tag_field) = match op.layout.variants {
|
||||
Variants::Single { index } => {
|
||||
let discr = match op.layout.ty.discriminant_for_variant(*self.tcx, index) {
|
||||
Some(discr) => {
|
||||
// This type actually has discriminants.
|
||||
assert_eq!(discr.ty, discr_layout.ty);
|
||||
Scalar::from_uint(discr.val, discr_layout.size)
|
||||
}
|
||||
None => {
|
||||
// On a type without actual discriminants, variant is 0.
|
||||
assert_eq!(index.as_u32(), 0);
|
||||
Scalar::from_uint(index.as_u32(), discr_layout.size)
|
||||
}
|
||||
};
|
||||
return Ok((discr, index));
|
||||
}
|
||||
Variants::Multiple { ref tag, ref tag_encoding, tag_field, .. } => {
|
||||
(tag, tag_encoding, tag_field)
|
||||
}
|
||||
};
|
||||
|
||||
// There are *three* layouts that come into play here:
|
||||
// - The discriminant has a type for typechecking. This is `discr_layout`, and is used for
|
||||
// the `Scalar` we return.
|
||||
// - The tag (encoded discriminant) has layout `tag_layout`. This is always an integer type,
|
||||
// and used to interpret the value we read from the tag field.
|
||||
// For the return value, a cast to `discr_layout` is performed.
|
||||
// - The field storing the tag has a layout, which is very similar to `tag_layout` but
|
||||
// may be a pointer. This is `tag_val.layout`; we just use it for sanity checks.
|
||||
|
||||
// Get layout for tag.
|
||||
let tag_layout = self.layout_of(tag_scalar_layout.value.to_int_ty(*self.tcx))?;
|
||||
|
||||
// Read tag and sanity-check `tag_layout`.
|
||||
let tag_val = self.read_immediate(&self.operand_field(op, tag_field)?)?;
|
||||
assert_eq!(tag_layout.size, tag_val.layout.size);
|
||||
assert_eq!(tag_layout.abi.is_signed(), tag_val.layout.abi.is_signed());
|
||||
let tag_val = tag_val.to_scalar()?;
|
||||
trace!("tag value: {:?}", tag_val);
|
||||
|
||||
// Figure out which discriminant and variant this corresponds to.
|
||||
Ok(match *tag_encoding {
|
||||
TagEncoding::Direct => {
|
||||
let tag_bits = tag_val
|
||||
.try_to_int()
|
||||
.map_err(|dbg_val| err_ub!(InvalidTag(dbg_val)))?
|
||||
.assert_bits(tag_layout.size);
|
||||
// Cast bits from tag layout to discriminant layout.
|
||||
let discr_val = self.cast_from_scalar(tag_bits, tag_layout, discr_layout.ty);
|
||||
let discr_bits = discr_val.assert_bits(discr_layout.size);
|
||||
// Convert discriminant to variant index, and catch invalid discriminants.
|
||||
let index = match *op.layout.ty.kind() {
|
||||
ty::Adt(adt, _) => {
|
||||
adt.discriminants(*self.tcx).find(|(_, var)| var.val == discr_bits)
|
||||
}
|
||||
ty::Generator(def_id, substs, _) => {
|
||||
let substs = substs.as_generator();
|
||||
substs
|
||||
.discriminants(def_id, *self.tcx)
|
||||
.find(|(_, var)| var.val == discr_bits)
|
||||
}
|
||||
_ => span_bug!(self.cur_span(), "tagged layout for non-adt non-generator"),
|
||||
}
|
||||
.ok_or_else(|| err_ub!(InvalidTag(Scalar::from_uint(tag_bits, tag_layout.size))))?;
|
||||
// Return the cast value, and the index.
|
||||
(discr_val, index.0)
|
||||
}
|
||||
TagEncoding::Niche { dataful_variant, ref niche_variants, niche_start } => {
|
||||
// Compute the variant this niche value/"tag" corresponds to. With niche layout,
|
||||
// discriminant (encoded in niche/tag) and variant index are the same.
|
||||
let variants_start = niche_variants.start().as_u32();
|
||||
let variants_end = niche_variants.end().as_u32();
|
||||
let variant = match tag_val.try_to_int() {
|
||||
Err(dbg_val) => {
|
||||
// So this is a pointer then, and casting to an int failed.
|
||||
// Can only happen during CTFE.
|
||||
let ptr = self.scalar_to_ptr(tag_val);
|
||||
// The niche must be just 0, and the ptr not null, then we know this is
|
||||
// okay. Everything else, we conservatively reject.
|
||||
let ptr_valid = niche_start == 0
|
||||
&& variants_start == variants_end
|
||||
&& !self.memory.ptr_may_be_null(ptr);
|
||||
if !ptr_valid {
|
||||
throw_ub!(InvalidTag(dbg_val))
|
||||
}
|
||||
dataful_variant
|
||||
}
|
||||
Ok(tag_bits) => {
|
||||
let tag_bits = tag_bits.assert_bits(tag_layout.size);
|
||||
// We need to use machine arithmetic to get the relative variant idx:
|
||||
// variant_index_relative = tag_val - niche_start_val
|
||||
let tag_val = ImmTy::from_uint(tag_bits, tag_layout);
|
||||
let niche_start_val = ImmTy::from_uint(niche_start, tag_layout);
|
||||
let variant_index_relative_val =
|
||||
self.binary_op(mir::BinOp::Sub, &tag_val, &niche_start_val)?;
|
||||
let variant_index_relative = variant_index_relative_val
|
||||
.to_scalar()?
|
||||
.assert_bits(tag_val.layout.size);
|
||||
// Check if this is in the range that indicates an actual discriminant.
|
||||
if variant_index_relative <= u128::from(variants_end - variants_start) {
|
||||
let variant_index_relative = u32::try_from(variant_index_relative)
|
||||
.expect("we checked that this fits into a u32");
|
||||
// Then computing the absolute variant idx should not overflow any more.
|
||||
let variant_index = variants_start
|
||||
.checked_add(variant_index_relative)
|
||||
.expect("overflow computing absolute variant idx");
|
||||
let variants_len = op
|
||||
.layout
|
||||
.ty
|
||||
.ty_adt_def()
|
||||
.expect("tagged layout for non adt")
|
||||
.variants
|
||||
.len();
|
||||
assert!(usize::try_from(variant_index).unwrap() < variants_len);
|
||||
VariantIdx::from_u32(variant_index)
|
||||
} else {
|
||||
dataful_variant
|
||||
}
|
||||
}
|
||||
};
|
||||
// Compute the size of the scalar we need to return.
|
||||
// No need to cast, because the variant index directly serves as discriminant and is
|
||||
// encoded in the tag.
|
||||
(Scalar::from_uint(variant.as_u32(), discr_layout.size), variant)
|
||||
}
|
||||
})
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user