From fcc4d8ce98ef61586fccfb7efae7563788453b73 Mon Sep 17 00:00:00 2001 From: b-naber Date: Tue, 29 Mar 2022 11:38:08 +0200 Subject: [PATCH] include refs in valtree creation --- .../rustc_const_eval/src/const_eval/mod.rs | 138 ++++++++++++++---- .../rustc_const_eval/src/interpret/operand.rs | 37 ++++- .../rustc_const_eval/src/interpret/place.rs | 12 ++ 3 files changed, 158 insertions(+), 29 deletions(-) diff --git a/compiler/rustc_const_eval/src/const_eval/mod.rs b/compiler/rustc_const_eval/src/const_eval/mod.rs index 6fd7f707e7e5..dad6e5e34a6c 100644 --- a/compiler/rustc_const_eval/src/const_eval/mod.rs +++ b/compiler/rustc_const_eval/src/const_eval/mod.rs @@ -6,9 +6,10 @@ use rustc_hir::Mutability; use rustc_middle::ty::{self, TyCtxt}; use rustc_middle::{ mir::{self, interpret::ConstAlloc}, - ty::ScalarInt, + ty::{ScalarInt, Ty}, }; 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, MPlaceTy, @@ -55,28 +56,43 @@ pub(crate) fn const_to_valtree<'tcx>( const_to_valtree_inner(&ecx, &place) } +#[instrument(skip(ecx), level = "debug")] +fn branches<'tcx>( + ecx: &CompileTimeEvalContext<'tcx, 'tcx>, + place: &MPlaceTy<'tcx>, + n: usize, + variant: Option, +) -> Option> { + let place = match variant { + Some(variant) => ecx.mplace_downcast(&place, variant).unwrap(), + None => *place, + }; + let variant = variant.map(|variant| Some(ty::ValTree::Leaf(ScalarInt::from(variant.as_u32())))); + debug!(?place, ?variant); + + let fields = (0..n).map(|i| { + let field = ecx.mplace_field(&place, i).unwrap(); + const_to_valtree_inner(ecx, &field) + }); + // For enums, we preped their variant index before the variant's fields so we can figure out + // the variant again when just seeing a valtree. + let branches = variant.into_iter().chain(fields); + Some(ty::ValTree::Branch(ecx.tcx.arena.alloc_from_iter(branches.collect::>>()?))) +} + +#[instrument(skip(ecx), level = "debug")] fn const_to_valtree_inner<'tcx>( ecx: &CompileTimeEvalContext<'tcx, 'tcx>, place: &MPlaceTy<'tcx>, ) -> Option> { - let branches = |n, variant| { - let place = match variant { - Some(variant) => ecx.mplace_downcast(&place, variant).unwrap(), - None => *place, - }; - let variant = - variant.map(|variant| Some(ty::ValTree::Leaf(ScalarInt::from(variant.as_u32())))); - let fields = (0..n).map(|i| { - let field = ecx.mplace_field(&place, i).unwrap(); - const_to_valtree_inner(ecx, &field) - }); - // For enums, we preped their variant index before the variant's fields so we can figure out - // the variant again when just seeing a valtree. - let branches = variant.into_iter().chain(fields); - Some(ty::ValTree::Branch( - ecx.tcx.arena.alloc_from_iter(branches.collect::>>()?), - )) + // We only want to use raw bytes in ValTrees for string slices or &[] + let use_bytes_for_ref = |ty: Ty<'tcx>| -> bool { + match ty.kind() { + ty::Str | ty::Char | ty::Uint(_) | ty::Int(_) | ty::Bool => true, + _ => false, + } }; + match place.layout.ty.kind() { ty::FnDef(..) => Some(ty::ValTree::zst()), ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Char => { @@ -90,7 +106,82 @@ fn const_to_valtree_inner<'tcx>( // Technically we could allow function pointers (represented as `ty::Instance`), but this is not guaranteed to // agree with runtime equality tests. ty::FnPtr(_) | ty::RawPtr(_) => None, - ty::Ref(..) => unimplemented!("need to use deref_const"), + + ty::Ref(_, ref_ty, _) if place.layout.ty.is_slice() => { + match ecx.try_read_immediate_from_mplace(&place) { + Ok(Some(imm)) => { + // `imm` is a ScalarPair. We try to get the underlying bytes behind that + // fat pointer for string slices and slices of integer types. For any other + // slice types we use `branches` to recursively construct the Valtree. + + if use_bytes_for_ref(*ref_ty) { + let (alloc, range) = ecx.get_alloc_from_imm_scalar_pair(imm); + let alloc_bytes = match alloc.get_bytes(&ecx.tcx, range) { + Ok(bytes) => bytes, + Err(_e) => return None, + }; + debug!(?alloc_bytes); + + let bytes = ecx.tcx.arena.alloc_slice(alloc_bytes); + let len = bytes.len(); + debug!(?bytes, ?len); + + let slice = ty::ValSlice { bytes}; + + Some(ty::ValTree::SliceOrStr(slice)) + } else { + let derefd = ecx.deref_operand(&imm.into()).expect(&format!("couldnt deref {:?}", imm)); + debug!("derefd: {:?}", derefd); + + let derefd_imm = match ecx.try_read_immediate_from_mplace(&derefd) { + Ok(Some(imm)) => imm, + _ => return None, + }; + debug!(?derefd_imm); + + let tcx = ecx.tcx.tcx; + let scalar_len= derefd.meta.unwrap_meta(); + let len = match scalar_len { + Scalar::Int(int) => { + int.try_to_machine_usize(tcx).expect(&format!("Expected a valid ScalarInt in {:?}", scalar_len)) + } + _ => bug!("expected a ScalarInt in meta data for {:?}", place), + }; + debug!(?len); + + let valtree = branches(ecx, place, len.try_into().expect("BLA"), None); + debug!(?valtree); + + valtree + } + } + _ => { + None + } + } + } + + ty::Ref(_, inner_ty, _) => { + debug!("Ref with inner_ty: {:?}", inner_ty); + let imm = ecx.try_read_immediate_from_mplace(&place).unwrap_or_else(|e| bug!("couldnt read immediate from {:?}, error: {:?}", place, e)); + match imm { + Some(imm) => { + debug!(?imm); + + let derefd_place = ecx.deref_mplace(place).unwrap_or_else(|e| bug!("couldn't deref {:?}, error: {:?}", place, e)); + debug!(?derefd_place); + + const_to_valtree_inner(ecx, &derefd_place) + } + None => None, + } + } + ty::Str => { + bug!("ty::Str should have been handled in ty::Ref branch that uses raw bytes"); + } + ty::Slice(_) => { + bug!("should have been handled in the Ref arm"); + } // Trait objects are not allowed in type level constants, as we have no concept for // resolving their backing type, even if we can do that at const eval time. We may @@ -98,11 +189,8 @@ fn const_to_valtree_inner<'tcx>( // but it is unclear if this is useful. ty::Dynamic(..) => None, - ty::Slice(_) | ty::Str => { - unimplemented!("need to find the backing data of the slice/str and recurse on that") - } - ty::Tuple(substs) => branches(substs.len(), None), - ty::Array(_, len) => branches(usize::try_from(len.eval_usize(ecx.tcx.tcx, ecx.param_env)).unwrap(), None), + ty::Tuple(substs) => branches(ecx, place, substs.len(), None), + ty::Array(_, len) => branches(ecx, place, usize::try_from(len.eval_usize(ecx.tcx.tcx, ecx.param_env)).unwrap(), None), ty::Adt(def, _) => { if def.variants().is_empty() { @@ -111,7 +199,7 @@ fn const_to_valtree_inner<'tcx>( let variant = ecx.read_discriminant(&place.into()).unwrap().1; - branches(def.variant(variant).fields.len(), def.is_enum().then_some(variant)) + branches(ecx, place, def.variant(variant).fields.len(), def.is_enum().then_some(variant)) } ty::Never diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs index 9000567558b8..d271bf53eac0 100644 --- a/compiler/rustc_const_eval/src/interpret/operand.rs +++ b/compiler/rustc_const_eval/src/interpret/operand.rs @@ -14,9 +14,9 @@ use rustc_target::abi::{Abi, HasDataLayout, Size, TagEncoding}; use rustc_target::abi::{VariantIdx, Variants}; use super::{ - alloc_range, from_known_layout, mir_assign_valid_types, AllocId, ConstValue, GlobalId, - InterpCx, InterpResult, MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Provenance, - Scalar, ScalarMaybeUninit, + alloc_range, from_known_layout, mir_assign_valid_types, AllocId, AllocRange, Allocation, + ConstValue, GlobalId, InterpCx, InterpResult, MPlaceTy, Machine, MemPlace, Place, PlaceTy, + Pointer, Provenance, Scalar, ScalarMaybeUninit, }; /// An `Immediate` represents a single immediate self-contained Rust value. @@ -248,7 +248,7 @@ impl<'tcx, Tag: Provenance> ImmTy<'tcx, Tag> { impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { /// Try reading an immediate in memory; this is interesting particularly for `ScalarPair`. /// Returns `None` if the layout does not permit loading this as a value. - fn try_read_immediate_from_mplace( + pub(crate) fn try_read_immediate_from_mplace( &self, mplace: &MPlaceTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx, Option>> { @@ -777,3 +777,32 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { }) } } + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx, PointerTag = AllocId>> InterpCx<'mir, 'tcx, M> { + pub fn get_alloc_from_imm_scalar_pair( + &self, + imm: ImmTy<'tcx, M::PointerTag>, + ) -> (&Allocation, AllocRange) { + match imm.imm { + Immediate::ScalarPair(a, b) => { + // We know `offset` is relative to the allocation, so we can use `into_parts`. + let (data, start) = match self.scalar_to_ptr(a.check_init().unwrap()).into_parts() { + (Some(alloc_id), offset) => { + (self.tcx.global_alloc(alloc_id).unwrap_memory(), offset.bytes()) + } + (None, _offset) => ( + self.tcx.intern_const_alloc(Allocation::from_bytes_byte_aligned_immutable( + b"" as &[u8], + )), + 0, + ), + }; + let len = b.to_machine_usize(self).unwrap(); + let size = Size::from_bytes(len); + let start = Size::from_bytes(start); + (data.inner(), AllocRange { start, size }) + } + _ => bug!("{:?} not a ScalarPair", imm), + } + } +} diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs index b1784b12c652..ad7620d83e67 100644 --- a/compiler/rustc_const_eval/src/interpret/place.rs +++ b/compiler/rustc_const_eval/src/interpret/place.rs @@ -305,6 +305,18 @@ where Ok(mplace) } + #[instrument(skip(self), level = "debug")] + pub fn deref_mplace( + &self, + src: &MPlaceTy<'tcx, M::PointerTag>, + ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> { + let val = self.try_read_immediate_from_mplace(src)?; + let mplace = self.ref_to_mplace(&val.unwrap())?; + self.check_mplace_access(mplace, CheckInAllocMsg::DerefTest)?; + + Ok(mplace) + } + #[inline] pub(super) fn get_alloc( &self,