diff options
Diffstat (limited to 'compiler/rustc_const_eval/src/interpret/cast.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/cast.rs | 365 |
1 files changed, 365 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs new file mode 100644 index 000000000..c97c31eb9 --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/cast.rs @@ -0,0 +1,365 @@ +use std::assert_matches::assert_matches; +use std::convert::TryFrom; + +use rustc_apfloat::ieee::{Double, Single}; +use rustc_apfloat::{Float, FloatConvert}; +use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar}; +use rustc_middle::mir::CastKind; +use rustc_middle::ty::adjustment::PointerCast; +use rustc_middle::ty::layout::{IntegerExt, LayoutOf, TyAndLayout}; +use rustc_middle::ty::{self, FloatTy, Ty, TypeAndMut}; +use rustc_target::abi::Integer; +use rustc_type_ir::sty::TyKind::*; + +use super::{ + util::ensure_monomorphic_enough, FnVal, ImmTy, Immediate, InterpCx, Machine, OpTy, PlaceTy, +}; + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + pub fn cast( + &mut self, + src: &OpTy<'tcx, M::Provenance>, + cast_kind: CastKind, + cast_ty: Ty<'tcx>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + use rustc_middle::mir::CastKind::*; + // FIXME: In which cases should we trigger UB when the source is uninit? + match cast_kind { + Pointer(PointerCast::Unsize) => { + let cast_ty = self.layout_of(cast_ty)?; + self.unsize_into(src, cast_ty, dest)?; + } + + PointerExposeAddress => { + let src = self.read_immediate(src)?; + let res = self.pointer_expose_address_cast(&src, cast_ty)?; + self.write_immediate(res, dest)?; + } + + PointerFromExposedAddress => { + let src = self.read_immediate(src)?; + let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?; + self.write_immediate(res, dest)?; + } + + Misc => { + let src = self.read_immediate(src)?; + let res = self.misc_cast(&src, cast_ty)?; + self.write_immediate(res, dest)?; + } + + Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer) => { + // These are NOPs, but can be wide pointers. + let v = self.read_immediate(src)?; + self.write_immediate(*v, dest)?; + } + + Pointer(PointerCast::ReifyFnPointer) => { + // The src operand does not matter, just its type + match *src.layout.ty.kind() { + ty::FnDef(def_id, substs) => { + // All reifications must be monomorphic, bail out otherwise. + ensure_monomorphic_enough(*self.tcx, src.layout.ty)?; + + let instance = ty::Instance::resolve_for_fn_ptr( + *self.tcx, + self.param_env, + def_id, + substs, + ) + .ok_or_else(|| err_inval!(TooGeneric))?; + + let fn_ptr = self.create_fn_alloc_ptr(FnVal::Instance(instance)); + self.write_pointer(fn_ptr, dest)?; + } + _ => span_bug!(self.cur_span(), "reify fn pointer on {:?}", src.layout.ty), + } + } + + Pointer(PointerCast::UnsafeFnPointer) => { + let src = self.read_immediate(src)?; + match cast_ty.kind() { + ty::FnPtr(_) => { + // No change to value + self.write_immediate(*src, dest)?; + } + _ => span_bug!(self.cur_span(), "fn to unsafe fn cast on {:?}", cast_ty), + } + } + + Pointer(PointerCast::ClosureFnPointer(_)) => { + // The src operand does not matter, just its type + match *src.layout.ty.kind() { + ty::Closure(def_id, substs) => { + // All reifications must be monomorphic, bail out otherwise. + ensure_monomorphic_enough(*self.tcx, src.layout.ty)?; + + let instance = ty::Instance::resolve_closure( + *self.tcx, + def_id, + substs, + ty::ClosureKind::FnOnce, + ) + .ok_or_else(|| err_inval!(TooGeneric))?; + let fn_ptr = self.create_fn_alloc_ptr(FnVal::Instance(instance)); + self.write_pointer(fn_ptr, dest)?; + } + _ => span_bug!(self.cur_span(), "closure fn pointer on {:?}", src.layout.ty), + } + } + } + Ok(()) + } + + pub fn misc_cast( + &mut self, + src: &ImmTy<'tcx, M::Provenance>, + cast_ty: Ty<'tcx>, + ) -> InterpResult<'tcx, Immediate<M::Provenance>> { + use rustc_type_ir::sty::TyKind::*; + trace!("Casting {:?}: {:?} to {:?}", *src, src.layout.ty, cast_ty); + + match src.layout.ty.kind() { + // Floating point + Float(FloatTy::F32) => { + return Ok(self.cast_from_float(src.to_scalar()?.to_f32()?, cast_ty).into()); + } + Float(FloatTy::F64) => { + return Ok(self.cast_from_float(src.to_scalar()?.to_f64()?, cast_ty).into()); + } + // The rest is integer/pointer-"like", including fn ptr casts + _ => assert!( + src.layout.ty.is_bool() + || src.layout.ty.is_char() + || src.layout.ty.is_integral() + || src.layout.ty.is_any_ptr(), + "Unexpected cast from type {:?}", + src.layout.ty + ), + } + + // # First handle non-scalar source values. + + // Handle casting any ptr to raw ptr (might be a fat ptr). + if src.layout.ty.is_any_ptr() && cast_ty.is_unsafe_ptr() { + let dest_layout = self.layout_of(cast_ty)?; + if dest_layout.size == src.layout.size { + // Thin or fat pointer that just hast the ptr kind of target type changed. + return Ok(**src); + } else { + // Casting the metadata away from a fat ptr. + assert_eq!(src.layout.size, 2 * self.pointer_size()); + assert_eq!(dest_layout.size, self.pointer_size()); + assert!(src.layout.ty.is_unsafe_ptr()); + return match **src { + Immediate::ScalarPair(data, _) => Ok(data.check_init()?.into()), + Immediate::Scalar(..) => span_bug!( + self.cur_span(), + "{:?} input to a fat-to-thin cast ({:?} -> {:?})", + *src, + src.layout.ty, + cast_ty + ), + Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)), + }; + } + } + + // # The remaining source values are scalar and "int-like". + let scalar = src.to_scalar()?; + Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into()) + } + + pub fn pointer_expose_address_cast( + &mut self, + src: &ImmTy<'tcx, M::Provenance>, + cast_ty: Ty<'tcx>, + ) -> InterpResult<'tcx, Immediate<M::Provenance>> { + assert_matches!(src.layout.ty.kind(), ty::RawPtr(_) | ty::FnPtr(_)); + assert!(cast_ty.is_integral()); + + let scalar = src.to_scalar()?; + let ptr = scalar.to_pointer(self)?; + match ptr.into_pointer_or_addr() { + Ok(ptr) => M::expose_ptr(self, ptr)?, + Err(_) => {} // Do nothing, exposing an invalid pointer (`None` provenance) is a NOP. + }; + Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into()) + } + + pub fn pointer_from_exposed_address_cast( + &mut self, + src: &ImmTy<'tcx, M::Provenance>, + cast_ty: Ty<'tcx>, + ) -> InterpResult<'tcx, Immediate<M::Provenance>> { + assert!(src.layout.ty.is_integral()); + assert_matches!(cast_ty.kind(), ty::RawPtr(_)); + + // First cast to usize. + let scalar = src.to_scalar()?; + let addr = self.cast_from_int_like(scalar, src.layout, self.tcx.types.usize)?; + let addr = addr.to_machine_usize(self)?; + + // Then turn address into pointer. + let ptr = M::ptr_from_addr_cast(&self, addr)?; + Ok(Scalar::from_maybe_pointer(ptr, self).into()) + } + + pub fn cast_from_int_like( + &self, + scalar: Scalar<M::Provenance>, // input value (there is no ScalarTy so we separate data+layout) + src_layout: TyAndLayout<'tcx>, + cast_ty: Ty<'tcx>, + ) -> InterpResult<'tcx, Scalar<M::Provenance>> { + // Let's make sure v is sign-extended *if* it has a signed type. + let signed = src_layout.abi.is_signed(); // Also asserts that abi is `Scalar`. + + let v = scalar.to_bits(src_layout.size)?; + let v = if signed { self.sign_extend(v, src_layout) } else { v }; + trace!("cast_from_scalar: {}, {} -> {}", v, src_layout.ty, cast_ty); + + Ok(match *cast_ty.kind() { + Int(_) | Uint(_) => { + let size = match *cast_ty.kind() { + Int(t) => Integer::from_int_ty(self, t).size(), + Uint(t) => Integer::from_uint_ty(self, t).size(), + _ => bug!(), + }; + let v = size.truncate(v); + Scalar::from_uint(v, size) + } + + Float(FloatTy::F32) if signed => Scalar::from_f32(Single::from_i128(v as i128).value), + Float(FloatTy::F64) if signed => Scalar::from_f64(Double::from_i128(v as i128).value), + Float(FloatTy::F32) => Scalar::from_f32(Single::from_u128(v).value), + Float(FloatTy::F64) => Scalar::from_f64(Double::from_u128(v).value), + + Char => { + // `u8` to `char` cast + Scalar::from_u32(u8::try_from(v).unwrap().into()) + } + + // Casts to bool are not permitted by rustc, no need to handle them here. + _ => span_bug!(self.cur_span(), "invalid int to {:?} cast", cast_ty), + }) + } + + fn cast_from_float<F>(&self, f: F, dest_ty: Ty<'tcx>) -> Scalar<M::Provenance> + where + F: Float + Into<Scalar<M::Provenance>> + FloatConvert<Single> + FloatConvert<Double>, + { + use rustc_type_ir::sty::TyKind::*; + match *dest_ty.kind() { + // float -> uint + Uint(t) => { + let size = Integer::from_uint_ty(self, t).size(); + // `to_u128` is a saturating cast, which is what we need + // (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r). + let v = f.to_u128(size.bits_usize()).value; + // This should already fit the bit width + Scalar::from_uint(v, size) + } + // float -> int + Int(t) => { + let size = Integer::from_int_ty(self, t).size(); + // `to_i128` is a saturating cast, which is what we need + // (https://doc.rust-lang.org/nightly/nightly-rustc/rustc_apfloat/trait.Float.html#method.to_i128_r). + let v = f.to_i128(size.bits_usize()).value; + Scalar::from_int(v, size) + } + // float -> f32 + Float(FloatTy::F32) => Scalar::from_f32(f.convert(&mut false).value), + // float -> f64 + Float(FloatTy::F64) => Scalar::from_f64(f.convert(&mut false).value), + // That's it. + _ => span_bug!(self.cur_span(), "invalid float to {:?} cast", dest_ty), + } + } + + fn unsize_into_ptr( + &mut self, + src: &OpTy<'tcx, M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + // The pointee types + source_ty: Ty<'tcx>, + cast_ty: Ty<'tcx>, + ) -> InterpResult<'tcx> { + // A<Struct> -> A<Trait> conversion + let (src_pointee_ty, dest_pointee_ty) = + self.tcx.struct_lockstep_tails_erasing_lifetimes(source_ty, cast_ty, self.param_env); + + match (&src_pointee_ty.kind(), &dest_pointee_ty.kind()) { + (&ty::Array(_, length), &ty::Slice(_)) => { + let ptr = self.read_immediate(src)?.to_scalar()?; + // u64 cast is from usize to u64, which is always good + let val = + Immediate::new_slice(ptr, length.eval_usize(*self.tcx, self.param_env), self); + self.write_immediate(val, dest) + } + (&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => { + let (old_data, old_vptr) = self.read_immediate(src)?.to_scalar_pair()?; + let old_vptr = old_vptr.to_pointer(self)?; + let (ty, old_trait) = self.get_ptr_vtable(old_vptr)?; + if old_trait != data_a.principal() { + throw_ub_format!("upcast on a pointer whose vtable does not match its type"); + } + let new_vptr = self.get_vtable_ptr(ty, data_b.principal())?; + self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest) + } + (_, &ty::Dynamic(ref data, _)) => { + // Initial cast from sized to dyn trait + let vtable = self.get_vtable_ptr(src_pointee_ty, data.principal())?; + let ptr = self.read_immediate(src)?.to_scalar()?; + let val = Immediate::new_dyn_trait(ptr, vtable, &*self.tcx); + self.write_immediate(val, dest) + } + + _ => { + span_bug!(self.cur_span(), "invalid unsizing {:?} -> {:?}", src.layout.ty, cast_ty) + } + } + } + + fn unsize_into( + &mut self, + src: &OpTy<'tcx, M::Provenance>, + cast_ty: TyAndLayout<'tcx>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + trace!("Unsizing {:?} of type {} into {:?}", *src, src.layout.ty, cast_ty.ty); + match (&src.layout.ty.kind(), &cast_ty.ty.kind()) { + (&ty::Ref(_, s, _), &ty::Ref(_, c, _) | &ty::RawPtr(TypeAndMut { ty: c, .. })) + | (&ty::RawPtr(TypeAndMut { ty: s, .. }), &ty::RawPtr(TypeAndMut { ty: c, .. })) => { + self.unsize_into_ptr(src, dest, *s, *c) + } + (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => { + assert_eq!(def_a, def_b); + + // unsizing of generic struct with pointer fields + // Example: `Arc<T>` -> `Arc<Trait>` + // here we need to increase the size of every &T thin ptr field to a fat ptr + for i in 0..src.layout.fields.count() { + let cast_ty_field = cast_ty.field(self, i); + if cast_ty_field.is_zst() { + continue; + } + let src_field = self.operand_field(src, i)?; + let dst_field = self.place_field(dest, i)?; + if src_field.layout.ty == cast_ty_field.ty { + self.copy_op(&src_field, &dst_field, /*allow_transmute*/ false)?; + } else { + self.unsize_into(&src_field, cast_ty_field, &dst_field)?; + } + } + Ok(()) + } + _ => span_bug!( + self.cur_span(), + "unsize_into: invalid conversion: {:?} -> {:?}", + src.layout, + dest.layout + ), + } + } +} |