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// Not in interpret to make sure we do not use private implementation details
use rustc_hir::Mutability;
use rustc_middle::mir;
use rustc_middle::mir::interpret::{EvalToValTreeResult, GlobalId};
use rustc_middle::ty::{self, TyCtxt};
use rustc_span::{source_map::DUMMY_SP, symbol::Symbol};
use rustc_target::abi::VariantIdx;
use crate::interpret::{
intern_const_alloc_recursive, ConstValue, InternKind, InterpCx, InterpResult, MemPlaceMeta,
Scalar,
};
mod error;
mod eval_queries;
mod fn_queries;
mod machine;
mod valtrees;
pub use error::*;
pub use eval_queries::*;
pub use fn_queries::*;
pub use machine::*;
pub(crate) use valtrees::{const_to_valtree_inner, valtree_to_const_value};
pub(crate) enum ValTreeCreationError {
NonSupportedType,
Other,
}
pub(crate) type ValTreeCreationResult<'tcx> = Result<ty::ValTree<'tcx>, ValTreeCreationError>;
pub(crate) fn const_caller_location(
tcx: TyCtxt<'_>,
(file, line, col): (Symbol, u32, u32),
) -> ConstValue<'_> {
trace!("const_caller_location: {}:{}:{}", file, line, col);
let mut ecx = mk_eval_cx(tcx, DUMMY_SP, ty::ParamEnv::reveal_all(), false);
let loc_place = ecx.alloc_caller_location(file, line, col);
if intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &loc_place).is_err() {
bug!("intern_const_alloc_recursive should not error in this case")
}
ConstValue::Scalar(Scalar::from_maybe_pointer(loc_place.ptr, &tcx))
}
/// Evaluates a constant and turns it into a type-level constant value.
pub(crate) fn eval_to_valtree<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
cid: GlobalId<'tcx>,
) -> EvalToValTreeResult<'tcx> {
let const_alloc = tcx.eval_to_allocation_raw(param_env.and(cid))?;
// FIXME Need to provide a span to `eval_to_valtree`
let ecx = mk_eval_cx(
tcx, DUMMY_SP, param_env,
// It is absolutely crucial for soundness that
// we do not read from static items or other mutable memory.
false,
);
let place = ecx.raw_const_to_mplace(const_alloc).unwrap();
debug!(?place);
let valtree_result = const_to_valtree_inner(&ecx, &place);
match valtree_result {
Ok(valtree) => Ok(Some(valtree)),
Err(_) => Ok(None),
}
}
/// Tries to destructure constants of type Array or Adt into the constants
/// of its fields.
pub(crate) fn try_destructure_const<'tcx>(
tcx: TyCtxt<'tcx>,
const_: ty::Const<'tcx>,
) -> Option<mir::DestructuredConst<'tcx>> {
if let ty::ConstKind::Value(valtree) = const_.val() {
let branches = match valtree {
ty::ValTree::Branch(b) => b,
_ => return None,
};
let (fields, variant) = match const_.ty().kind() {
ty::Array(inner_ty, _) | ty::Slice(inner_ty) => {
// construct the consts for the elements of the array/slice
let field_consts = branches
.iter()
.map(|b| {
tcx.mk_const(ty::ConstS { kind: ty::ConstKind::Value(*b), ty: *inner_ty })
})
.collect::<Vec<_>>();
debug!(?field_consts);
(field_consts, None)
}
ty::Adt(def, _) if def.variants().is_empty() => bug!("unreachable"),
ty::Adt(def, substs) => {
let variant_idx = if def.is_enum() {
VariantIdx::from_u32(branches[0].unwrap_leaf().try_to_u32().ok()?)
} else {
VariantIdx::from_u32(0)
};
let fields = &def.variant(variant_idx).fields;
let mut field_consts = Vec::with_capacity(fields.len());
// Note: First element inValTree corresponds to variant of enum
let mut valtree_idx = if def.is_enum() { 1 } else { 0 };
for field in fields {
let field_ty = field.ty(tcx, substs);
let field_valtree = branches[valtree_idx]; // first element of branches is variant
let field_const = tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Value(field_valtree),
ty: field_ty,
});
field_consts.push(field_const);
valtree_idx += 1;
}
debug!(?field_consts);
(field_consts, Some(variant_idx))
}
ty::Tuple(elem_tys) => {
let fields = elem_tys
.iter()
.enumerate()
.map(|(i, elem_ty)| {
let elem_valtree = branches[i];
tcx.mk_const(ty::ConstS {
kind: ty::ConstKind::Value(elem_valtree),
ty: elem_ty,
})
})
.collect::<Vec<_>>();
(fields, None)
}
_ => bug!("cannot destructure constant {:?}", const_),
};
let fields = tcx.arena.alloc_from_iter(fields.into_iter());
Some(mir::DestructuredConst { variant, fields })
} else {
None
}
}
#[instrument(skip(tcx), level = "debug")]
pub(crate) fn try_destructure_mir_constant<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
val: mir::ConstantKind<'tcx>,
) -> InterpResult<'tcx, mir::DestructuredMirConstant<'tcx>> {
trace!("destructure_mir_constant: {:?}", val);
let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
let op = ecx.mir_const_to_op(&val, None)?;
// We go to `usize` as we cannot allocate anything bigger anyway.
let (field_count, variant, down) = match val.ty().kind() {
ty::Array(_, len) => (len.eval_usize(tcx, param_env) as usize, None, op),
ty::Adt(def, _) if def.variants().is_empty() => {
throw_ub!(Unreachable)
}
ty::Adt(def, _) => {
let variant = ecx.read_discriminant(&op)?.1;
let down = ecx.operand_downcast(&op, variant)?;
(def.variants()[variant].fields.len(), Some(variant), down)
}
ty::Tuple(substs) => (substs.len(), None, op),
_ => bug!("cannot destructure mir constant {:?}", val),
};
let fields_iter = (0..field_count)
.map(|i| {
let field_op = ecx.operand_field(&down, i)?;
let val = op_to_const(&ecx, &field_op);
Ok(mir::ConstantKind::Val(val, field_op.layout.ty))
})
.collect::<InterpResult<'tcx, Vec<_>>>()?;
let fields = tcx.arena.alloc_from_iter(fields_iter);
Ok(mir::DestructuredMirConstant { variant, fields })
}
#[instrument(skip(tcx), level = "debug")]
pub(crate) fn deref_mir_constant<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
val: mir::ConstantKind<'tcx>,
) -> mir::ConstantKind<'tcx> {
let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
let op = ecx.mir_const_to_op(&val, None).unwrap();
let mplace = ecx.deref_operand(&op).unwrap();
if let Some(alloc_id) = mplace.ptr.provenance {
assert_eq!(
tcx.get_global_alloc(alloc_id).unwrap().unwrap_memory().0 .0.mutability,
Mutability::Not,
"deref_mir_constant cannot be used with mutable allocations as \
that could allow pattern matching to observe mutable statics",
);
}
let ty = match mplace.meta {
MemPlaceMeta::None => mplace.layout.ty,
MemPlaceMeta::Poison => bug!("poison metadata in `deref_mir_constant`: {:#?}", mplace),
// In case of unsized types, figure out the real type behind.
MemPlaceMeta::Meta(scalar) => match mplace.layout.ty.kind() {
ty::Str => bug!("there's no sized equivalent of a `str`"),
ty::Slice(elem_ty) => tcx.mk_array(*elem_ty, scalar.to_machine_usize(&tcx).unwrap()),
_ => bug!(
"type {} should not have metadata, but had {:?}",
mplace.layout.ty,
mplace.meta
),
},
};
mir::ConstantKind::Val(op_to_const(&ecx, &mplace.into()), ty)
}
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