diff options
| -rw-r--r-- | src/librustc_mir/const_eval/query.rs | 276 |
1 files changed, 138 insertions, 138 deletions
diff --git a/src/librustc_mir/const_eval/query.rs b/src/librustc_mir/const_eval/query.rs index f92475e0375..2aeb6df6dd6 100644 --- a/src/librustc_mir/const_eval/query.rs +++ b/src/librustc_mir/const_eval/query.rs @@ -21,6 +21,144 @@ pub fn note_on_undefined_behavior_error() -> &'static str { repository if you believe it should not be considered undefined behavior." } +// Returns a pointer to where the result lives +fn eval_body_using_ecx<'mir, 'tcx>( + ecx: &mut CompileTimeEvalContext<'mir, 'tcx>, + cid: GlobalId<'tcx>, + body: &'mir mir::Body<'tcx>, +) -> InterpResult<'tcx, MPlaceTy<'tcx>> { + debug!("eval_body_using_ecx: {:?}, {:?}", cid, ecx.param_env); + let tcx = ecx.tcx.tcx; + let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?; + assert!(!layout.is_unsized()); + let ret = ecx.allocate(layout, MemoryKind::Stack); + + let name = ty::tls::with(|tcx| tcx.def_path_str(cid.instance.def_id())); + let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p)); + trace!("eval_body_using_ecx: pushing stack frame for global: {}{}", name, prom); + + // Assert all args (if any) are zero-sized types; `eval_body_using_ecx` doesn't + // make sense if the body is expecting nontrivial arguments. + // (The alternative would be to use `eval_fn_call` with an args slice.) + for arg in body.args_iter() { + let decl = body.local_decls.get(arg).expect("arg missing from local_decls"); + let layout = ecx.layout_of(decl.ty.subst(tcx, cid.instance.substs))?; + assert!(layout.is_zst()) + } + + ecx.push_stack_frame( + cid.instance, + body.span, + body, + Some(ret.into()), + StackPopCleanup::None { cleanup: false }, + )?; + + // The main interpreter loop. + ecx.run()?; + + // Intern the result + intern_const_alloc_recursive(ecx, tcx.static_mutability(cid.instance.def_id()), ret)?; + + debug!("eval_body_using_ecx done: {:?}", *ret); + Ok(ret) +} + +/// The `InterpCx` is only meant to be used to do field and index projections into constants for +/// `simd_shuffle` and const patterns in match arms. +/// +/// The function containing the `match` that is currently being analyzed may have generic bounds +/// that inform us about the generic bounds of the constant. E.g., using an associated constant +/// of a function's generic parameter will require knowledge about the bounds on the generic +/// parameter. These bounds are passed to `mk_eval_cx` via the `ParamEnv` argument. +pub(super) fn mk_eval_cx<'mir, 'tcx>( + tcx: TyCtxt<'tcx>, + span: Span, + param_env: ty::ParamEnv<'tcx>, + can_access_statics: bool, +) -> CompileTimeEvalContext<'mir, 'tcx> { + debug!("mk_eval_cx: {:?}", param_env); + InterpCx::new( + tcx.at(span), + param_env, + CompileTimeInterpreter::new(), + MemoryExtra { can_access_statics }, + ) +} + +pub(super) fn op_to_const<'tcx>( + ecx: &CompileTimeEvalContext<'_, 'tcx>, + op: OpTy<'tcx>, +) -> &'tcx ty::Const<'tcx> { + // We do not have value optimizations for everything. + // Only scalars and slices, since they are very common. + // Note that further down we turn scalars of undefined bits back to `ByRef`. These can result + // from scalar unions that are initialized with one of their zero sized variants. We could + // instead allow `ConstValue::Scalar` to store `ScalarMaybeUndef`, but that would affect all + // the usual cases of extracting e.g. a `usize`, without there being a real use case for the + // `Undef` situation. + let try_as_immediate = match op.layout.abi { + layout::Abi::Scalar(..) => true, + layout::Abi::ScalarPair(..) => match op.layout.ty.kind { + ty::Ref(_, inner, _) => match inner.kind { + ty::Slice(elem) => elem == ecx.tcx.types.u8, + ty::Str => true, + _ => false, + }, + _ => false, + }, + _ => false, + }; + let immediate = if try_as_immediate { + Err(ecx.read_immediate(op).expect("normalization works on validated constants")) + } else { + // It is guaranteed that any non-slice scalar pair is actually ByRef here. + // When we come back from raw const eval, we are always by-ref. The only way our op here is + // by-val is if we are in const_field, i.e., if this is (a field of) something that we + // "tried to make immediate" before. We wouldn't do that for non-slice scalar pairs or + // structs containing such. + op.try_as_mplace() + }; + let val = match immediate { + Ok(mplace) => { + let ptr = mplace.ptr.to_ptr().unwrap(); + let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); + ConstValue::ByRef { alloc, offset: ptr.offset } + } + // see comment on `let try_as_immediate` above + Err(ImmTy { imm: Immediate::Scalar(x), .. }) => match x { + ScalarMaybeUndef::Scalar(s) => ConstValue::Scalar(s), + ScalarMaybeUndef::Undef => { + // When coming out of "normal CTFE", we'll always have an `Indirect` operand as + // argument and we will not need this. The only way we can already have an + // `Immediate` is when we are called from `const_field`, and that `Immediate` + // comes from a constant so it can happen have `Undef`, because the indirect + // memory that was read had undefined bytes. + let mplace = op.assert_mem_place(); + let ptr = mplace.ptr.to_ptr().unwrap(); + let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); + ConstValue::ByRef { alloc, offset: ptr.offset } + } + }, + Err(ImmTy { imm: Immediate::ScalarPair(a, b), .. }) => { + let (data, start) = match a.not_undef().unwrap() { + Scalar::Ptr(ptr) => { + (ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id), ptr.offset.bytes()) + } + Scalar::Raw { .. } => ( + ecx.tcx.intern_const_alloc(Allocation::from_byte_aligned_bytes(b"" as &[u8])), + 0, + ), + }; + let len = b.to_machine_usize(&ecx.tcx.tcx).unwrap(); + let start = start.try_into().unwrap(); + let len: usize = len.try_into().unwrap(); + ConstValue::Slice { data, start, end: start + len } + } + }; + ecx.tcx.mk_const(ty::Const { val: ty::ConstKind::Value(val), ty: op.layout.ty }) +} + fn validate_and_turn_into_const<'tcx>( tcx: TyCtxt<'tcx>, constant: RawConst<'tcx>, @@ -219,141 +357,3 @@ pub fn const_eval_raw_provider<'tcx>( } }) } - -// Returns a pointer to where the result lives -fn eval_body_using_ecx<'mir, 'tcx>( - ecx: &mut CompileTimeEvalContext<'mir, 'tcx>, - cid: GlobalId<'tcx>, - body: &'mir mir::Body<'tcx>, -) -> InterpResult<'tcx, MPlaceTy<'tcx>> { - debug!("eval_body_using_ecx: {:?}, {:?}", cid, ecx.param_env); - let tcx = ecx.tcx.tcx; - let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?; - assert!(!layout.is_unsized()); - let ret = ecx.allocate(layout, MemoryKind::Stack); - - let name = ty::tls::with(|tcx| tcx.def_path_str(cid.instance.def_id())); - let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p)); - trace!("eval_body_using_ecx: pushing stack frame for global: {}{}", name, prom); - - // Assert all args (if any) are zero-sized types; `eval_body_using_ecx` doesn't - // make sense if the body is expecting nontrivial arguments. - // (The alternative would be to use `eval_fn_call` with an args slice.) - for arg in body.args_iter() { - let decl = body.local_decls.get(arg).expect("arg missing from local_decls"); - let layout = ecx.layout_of(decl.ty.subst(tcx, cid.instance.substs))?; - assert!(layout.is_zst()) - } - - ecx.push_stack_frame( - cid.instance, - body.span, - body, - Some(ret.into()), - StackPopCleanup::None { cleanup: false }, - )?; - - // The main interpreter loop. - ecx.run()?; - - // Intern the result - intern_const_alloc_recursive(ecx, tcx.static_mutability(cid.instance.def_id()), ret)?; - - debug!("eval_body_using_ecx done: {:?}", *ret); - Ok(ret) -} - -/// The `InterpCx` is only meant to be used to do field and index projections into constants for -/// `simd_shuffle` and const patterns in match arms. -/// -/// The function containing the `match` that is currently being analyzed may have generic bounds -/// that inform us about the generic bounds of the constant. E.g., using an associated constant -/// of a function's generic parameter will require knowledge about the bounds on the generic -/// parameter. These bounds are passed to `mk_eval_cx` via the `ParamEnv` argument. -pub(super) fn mk_eval_cx<'mir, 'tcx>( - tcx: TyCtxt<'tcx>, - span: Span, - param_env: ty::ParamEnv<'tcx>, - can_access_statics: bool, -) -> CompileTimeEvalContext<'mir, 'tcx> { - debug!("mk_eval_cx: {:?}", param_env); - InterpCx::new( - tcx.at(span), - param_env, - CompileTimeInterpreter::new(), - MemoryExtra { can_access_statics }, - ) -} - -pub(super) fn op_to_const<'tcx>( - ecx: &CompileTimeEvalContext<'_, 'tcx>, - op: OpTy<'tcx>, -) -> &'tcx ty::Const<'tcx> { - // We do not have value optimizations for everything. - // Only scalars and slices, since they are very common. - // Note that further down we turn scalars of undefined bits back to `ByRef`. These can result - // from scalar unions that are initialized with one of their zero sized variants. We could - // instead allow `ConstValue::Scalar` to store `ScalarMaybeUndef`, but that would affect all - // the usual cases of extracting e.g. a `usize`, without there being a real use case for the - // `Undef` situation. - let try_as_immediate = match op.layout.abi { - layout::Abi::Scalar(..) => true, - layout::Abi::ScalarPair(..) => match op.layout.ty.kind { - ty::Ref(_, inner, _) => match inner.kind { - ty::Slice(elem) => elem == ecx.tcx.types.u8, - ty::Str => true, - _ => false, - }, - _ => false, - }, - _ => false, - }; - let immediate = if try_as_immediate { - Err(ecx.read_immediate(op).expect("normalization works on validated constants")) - } else { - // It is guaranteed that any non-slice scalar pair is actually ByRef here. - // When we come back from raw const eval, we are always by-ref. The only way our op here is - // by-val is if we are in const_field, i.e., if this is (a field of) something that we - // "tried to make immediate" before. We wouldn't do that for non-slice scalar pairs or - // structs containing such. - op.try_as_mplace() - }; - let val = match immediate { - Ok(mplace) => { - let ptr = mplace.ptr.to_ptr().unwrap(); - let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); - ConstValue::ByRef { alloc, offset: ptr.offset } - } - // see comment on `let try_as_immediate` above - Err(ImmTy { imm: Immediate::Scalar(x), .. }) => match x { - ScalarMaybeUndef::Scalar(s) => ConstValue::Scalar(s), - ScalarMaybeUndef::Undef => { - // When coming out of "normal CTFE", we'll always have an `Indirect` operand as - // argument and we will not need this. The only way we can already have an - // `Immediate` is when we are called from `const_field`, and that `Immediate` - // comes from a constant so it can happen have `Undef`, because the indirect - // memory that was read had undefined bytes. - let mplace = op.assert_mem_place(); - let ptr = mplace.ptr.to_ptr().unwrap(); - let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); - ConstValue::ByRef { alloc, offset: ptr.offset } - } - }, - Err(ImmTy { imm: Immediate::ScalarPair(a, b), .. }) => { - let (data, start) = match a.not_undef().unwrap() { - Scalar::Ptr(ptr) => { - (ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id), ptr.offset.bytes()) - } - Scalar::Raw { .. } => ( - ecx.tcx.intern_const_alloc(Allocation::from_byte_aligned_bytes(b"" as &[u8])), - 0, - ), - }; - let len = b.to_machine_usize(&ecx.tcx.tcx).unwrap(); - let start = start.try_into().unwrap(); - let len: usize = len.try_into().unwrap(); - ConstValue::Slice { data, start, end: start + len } - } - }; - ecx.tcx.mk_const(ty::Const { val: ty::ConstKind::Value(val), ty: op.layout.ty }) -} |