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3dfed10e XL |
1 | use crate::mir::interpret::ConstValue; |
2 | use crate::mir::interpret::{LitToConstInput, Scalar}; | |
3 | use crate::ty::subst::InternalSubsts; | |
4 | use crate::ty::{self, Ty, TyCtxt}; | |
5 | use crate::ty::{ParamEnv, ParamEnvAnd}; | |
6 | use rustc_errors::ErrorReported; | |
7 | use rustc_hir as hir; | |
8 | use rustc_hir::def_id::LocalDefId; | |
9 | use rustc_macros::HashStable; | |
10 | ||
11 | mod int; | |
12 | mod kind; | |
6a06907d | 13 | mod valtree; |
3dfed10e XL |
14 | |
15 | pub use int::*; | |
16 | pub use kind::*; | |
6a06907d | 17 | pub use valtree::*; |
3dfed10e XL |
18 | |
19 | /// Typed constant value. | |
20 | #[derive(Copy, Clone, Debug, Hash, TyEncodable, TyDecodable, Eq, PartialEq, Ord, PartialOrd)] | |
21 | #[derive(HashStable)] | |
22 | pub struct Const<'tcx> { | |
23 | pub ty: Ty<'tcx>, | |
24 | ||
25 | pub val: ConstKind<'tcx>, | |
f035d41b XL |
26 | } |
27 | ||
6a06907d | 28 | #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
3dfed10e XL |
29 | static_assert_size!(Const<'_>, 48); |
30 | ||
31 | impl<'tcx> Const<'tcx> { | |
32 | /// Literals and const generic parameters are eagerly converted to a constant, everything else | |
33 | /// becomes `Unevaluated`. | |
34 | pub fn from_anon_const(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx Self { | |
35 | Self::from_opt_const_arg_anon_const(tcx, ty::WithOptConstParam::unknown(def_id)) | |
f035d41b | 36 | } |
f035d41b | 37 | |
3dfed10e XL |
38 | pub fn from_opt_const_arg_anon_const( |
39 | tcx: TyCtxt<'tcx>, | |
40 | def: ty::WithOptConstParam<LocalDefId>, | |
41 | ) -> &'tcx Self { | |
42 | debug!("Const::from_anon_const(def={:?})", def); | |
43 | ||
44 | let hir_id = tcx.hir().local_def_id_to_hir_id(def.did); | |
45 | ||
46 | let body_id = match tcx.hir().get(hir_id) { | |
47 | hir::Node::AnonConst(ac) => ac.body, | |
48 | _ => span_bug!( | |
49 | tcx.def_span(def.did.to_def_id()), | |
50 | "from_anon_const can only process anonymous constants" | |
51 | ), | |
52 | }; | |
53 | ||
54 | let expr = &tcx.hir().body(body_id).value; | |
55 | ||
56 | let ty = tcx.type_of(def.def_id_for_type_of()); | |
57 | ||
58 | let lit_input = match expr.kind { | |
59 | hir::ExprKind::Lit(ref lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }), | |
6a06907d | 60 | hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => match expr.kind { |
3dfed10e XL |
61 | hir::ExprKind::Lit(ref lit) => { |
62 | Some(LitToConstInput { lit: &lit.node, ty, neg: true }) | |
f035d41b | 63 | } |
3dfed10e XL |
64 | _ => None, |
65 | }, | |
66 | _ => None, | |
67 | }; | |
68 | ||
69 | if let Some(lit_input) = lit_input { | |
70 | // If an error occurred, ignore that it's a literal and leave reporting the error up to | |
71 | // mir. | |
72 | if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) { | |
73 | return c; | |
f035d41b | 74 | } else { |
3dfed10e | 75 | tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const"); |
f035d41b | 76 | } |
3dfed10e XL |
77 | } |
78 | ||
79 | // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments | |
80 | // currently have to be wrapped in curly brackets, so it's necessary to special-case. | |
81 | let expr = match &expr.kind { | |
82 | hir::ExprKind::Block(block, _) if block.stmts.is_empty() && block.expr.is_some() => { | |
83 | block.expr.as_ref().unwrap() | |
84 | } | |
85 | _ => expr, | |
86 | }; | |
87 | ||
88 | use hir::{def::DefKind::ConstParam, def::Res, ExprKind, Path, QPath}; | |
89 | let val = match expr.kind { | |
90 | ExprKind::Path(QPath::Resolved(_, &Path { res: Res::Def(ConstParam, def_id), .. })) => { | |
91 | // Find the name and index of the const parameter by indexing the generics of | |
92 | // the parent item and construct a `ParamConst`. | |
93 | let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); | |
94 | let item_id = tcx.hir().get_parent_node(hir_id); | |
95 | let item_def_id = tcx.hir().local_def_id(item_id); | |
96 | let generics = tcx.generics_of(item_def_id.to_def_id()); | |
5869c6ff | 97 | let index = generics.param_def_id_to_index[&def_id]; |
3dfed10e XL |
98 | let name = tcx.hir().name(hir_id); |
99 | ty::ConstKind::Param(ty::ParamConst::new(index, name)) | |
f035d41b | 100 | } |
3dfed10e XL |
101 | _ => ty::ConstKind::Unevaluated( |
102 | def.to_global(), | |
103 | InternalSubsts::identity_for_item(tcx, def.did.to_def_id()), | |
104 | None, | |
105 | ), | |
106 | }; | |
107 | ||
108 | tcx.mk_const(ty::Const { val, ty }) | |
109 | } | |
110 | ||
111 | #[inline] | |
112 | /// Interns the given value as a constant. | |
113 | pub fn from_value(tcx: TyCtxt<'tcx>, val: ConstValue<'tcx>, ty: Ty<'tcx>) -> &'tcx Self { | |
114 | tcx.mk_const(Self { val: ConstKind::Value(val), ty }) | |
115 | } | |
116 | ||
117 | #[inline] | |
118 | /// Interns the given scalar as a constant. | |
119 | pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self { | |
120 | Self::from_value(tcx, ConstValue::Scalar(val), ty) | |
121 | } | |
122 | ||
123 | #[inline] | |
124 | /// Creates a constant with the given integer value and interns it. | |
125 | pub fn from_bits(tcx: TyCtxt<'tcx>, bits: u128, ty: ParamEnvAnd<'tcx, Ty<'tcx>>) -> &'tcx Self { | |
126 | let size = tcx | |
127 | .layout_of(ty) | |
128 | .unwrap_or_else(|e| panic!("could not compute layout for {:?}: {:?}", ty, e)) | |
129 | .size; | |
130 | Self::from_scalar(tcx, Scalar::from_uint(bits, size), ty.value) | |
131 | } | |
132 | ||
133 | #[inline] | |
134 | /// Creates an interned zst constant. | |
135 | pub fn zero_sized(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> &'tcx Self { | |
29967ef6 | 136 | Self::from_scalar(tcx, Scalar::ZST, ty) |
3dfed10e XL |
137 | } |
138 | ||
139 | #[inline] | |
140 | /// Creates an interned bool constant. | |
141 | pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> &'tcx Self { | |
142 | Self::from_bits(tcx, v as u128, ParamEnv::empty().and(tcx.types.bool)) | |
143 | } | |
144 | ||
145 | #[inline] | |
146 | /// Creates an interned usize constant. | |
147 | pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> &'tcx Self { | |
148 | Self::from_bits(tcx, n as u128, ParamEnv::empty().and(tcx.types.usize)) | |
149 | } | |
150 | ||
151 | #[inline] | |
152 | /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of | |
153 | /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it | |
154 | /// contains const generic parameters or pointers). | |
155 | pub fn try_eval_bits( | |
156 | &self, | |
157 | tcx: TyCtxt<'tcx>, | |
158 | param_env: ParamEnv<'tcx>, | |
159 | ty: Ty<'tcx>, | |
160 | ) -> Option<u128> { | |
161 | assert_eq!(self.ty, ty); | |
162 | let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size; | |
163 | // if `ty` does not depend on generic parameters, use an empty param_env | |
164 | self.val.eval(tcx, param_env).try_to_bits(size) | |
165 | } | |
166 | ||
167 | #[inline] | |
168 | pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> { | |
169 | self.val.eval(tcx, param_env).try_to_bool() | |
170 | } | |
171 | ||
172 | #[inline] | |
173 | pub fn try_eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u64> { | |
174 | self.val.eval(tcx, param_env).try_to_machine_usize(tcx) | |
175 | } | |
176 | ||
177 | #[inline] | |
178 | /// Tries to evaluate the constant if it is `Unevaluated`. If that doesn't succeed, return the | |
179 | /// unevaluated constant. | |
180 | pub fn eval(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> &Const<'tcx> { | |
181 | if let Some(val) = self.val.try_eval(tcx, param_env) { | |
182 | match val { | |
183 | Ok(val) => Const::from_value(tcx, val, self.ty), | |
184 | Err(ErrorReported) => tcx.const_error(self.ty), | |
185 | } | |
186 | } else { | |
187 | self | |
f035d41b XL |
188 | } |
189 | } | |
3dfed10e XL |
190 | |
191 | #[inline] | |
192 | /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type. | |
193 | pub fn eval_bits(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> u128 { | |
194 | self.try_eval_bits(tcx, param_env, ty) | |
195 | .unwrap_or_else(|| bug!("expected bits of {:#?}, got {:#?}", ty, self)) | |
196 | } | |
197 | ||
198 | #[inline] | |
199 | /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`. | |
200 | pub fn eval_usize(&self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 { | |
201 | self.try_eval_usize(tcx, param_env) | |
202 | .unwrap_or_else(|| bug!("expected usize, got {:#?}", self)) | |
203 | } | |
f035d41b | 204 | } |