diff options
Diffstat (limited to 'compiler/rustc_const_eval/src/const_eval/mod.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/const_eval/mod.rs | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/const_eval/mod.rs b/compiler/rustc_const_eval/src/const_eval/mod.rs new file mode 100644 index 000000000..948c33494 --- /dev/null +++ b/compiler/rustc_const_eval/src/const_eval/mod.rs @@ -0,0 +1,163 @@ +// 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 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) 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)) +} + +// We forbid type-level constants that contain more than `VALTREE_MAX_NODES` nodes. +const VALTREE_MAX_NODES: usize = 100000; + +pub(crate) enum ValTreeCreationError { + NodesOverflow, + NonSupportedType, + Other, +} +pub(crate) type ValTreeCreationResult<'tcx> = Result<ty::ValTree<'tcx>, ValTreeCreationError>; + +/// 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 mut num_nodes = 0; + let valtree_result = const_to_valtree_inner(&ecx, &place, &mut num_nodes); + + match valtree_result { + Ok(valtree) => Ok(Some(valtree)), + Err(err) => { + let did = cid.instance.def_id(); + let s = cid.display(tcx); + match err { + ValTreeCreationError::NodesOverflow => { + let msg = format!("maximum number of nodes exceeded in constant {}", &s); + let mut diag = match tcx.hir().span_if_local(did) { + Some(span) => tcx.sess.struct_span_err(span, &msg), + None => tcx.sess.struct_err(&msg), + }; + diag.emit(); + + Ok(None) + } + ValTreeCreationError::NonSupportedType | ValTreeCreationError::Other => Ok(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.global_alloc(alloc_id).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, + // 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) +} |