1 // Copyright 2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! This module contains the `EvalContext` methods for executing a single step of the interpreter.
13 //! The main entry point is the `step` method.
16 use rustc::ty::layout::LayoutOf;
17 use rustc::mir::interpret::{EvalResult, Scalar, PointerArithmetic};
19 use super::{EvalContext, Machine};
21 /// Classify whether an operator is "left-homogeneous", i.e. the LHS has the
22 /// same type as the result.
24 fn binop_left_homogeneous(op: mir::BinOp) -> bool {
25 use rustc::mir::BinOp::*;
27 Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr |
30 Eq | Ne | Lt | Le | Gt | Ge =>
34 /// Classify whether an operator is "right-homogeneous", i.e. the RHS has the
35 /// same type as the LHS.
37 fn binop_right_homogeneous(op: mir::BinOp) -> bool {
38 use rustc::mir::BinOp::*;
40 Add | Sub | Mul | Div | Rem | BitXor | BitAnd | BitOr |
41 Eq | Ne | Lt | Le | Gt | Ge =>
48 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
49 pub fn run(&mut self) -> EvalResult<'tcx> {
54 /// Returns true as long as there are more things to do.
55 fn step(&mut self) -> EvalResult<'tcx, bool> {
56 if self.stack.is_empty() {
60 let block = self.frame().block;
61 let stmt_id = self.frame().stmt;
63 let basic_block = &mir.basic_blocks()[block];
65 let old_frames = self.cur_frame();
67 if let Some(stmt) = basic_block.statements.get(stmt_id) {
68 assert_eq!(old_frames, self.cur_frame());
69 self.statement(stmt)?;
73 M::before_terminator(self)?;
75 let terminator = basic_block.terminator();
76 assert_eq!(old_frames, self.cur_frame());
77 self.terminator(terminator)?;
81 fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> EvalResult<'tcx> {
84 use rustc::mir::StatementKind::*;
86 // Some statements (e.g. box) push new stack frames.
87 // We have to record the stack frame number *before* executing the statement.
88 let frame_idx = self.cur_frame();
89 self.tcx.span = stmt.source_info.span;
90 self.memory.tcx.span = stmt.source_info.span;
93 Assign(ref place, ref rvalue) => self.eval_rvalue_into_place(rvalue, place)?,
99 let dest = self.eval_place(place)?;
100 self.write_discriminant_index(variant_index, dest)?;
103 // Mark locals as alive
104 StorageLive(local) => {
105 let old_val = self.storage_live(local)?;
106 self.deallocate_local(old_val)?;
109 // Mark locals as dead
110 StorageDead(local) => {
111 let old_val = self.storage_dead(local);
112 self.deallocate_local(old_val)?;
115 // No dynamic semantics attached to `FakeRead`; MIR
116 // interpreter is solely intended for borrowck'ed code.
120 Validate(op, ref places) => {
121 for operand in places {
122 M::validation_op(self, op, operand)?;
127 AscribeUserType(..) => {}
129 // Defined to do nothing. These are added by optimization passes, to avoid changing the
130 // size of MIR constantly.
133 InlineAsm { .. } => return err!(InlineAsm),
136 self.stack[frame_idx].stmt += 1;
140 /// Evaluate an assignment statement.
142 /// There is no separate `eval_rvalue` function. Instead, the code for handling each rvalue
143 /// type writes its results directly into the memory specified by the place.
144 fn eval_rvalue_into_place(
146 rvalue: &mir::Rvalue<'tcx>,
147 place: &mir::Place<'tcx>,
148 ) -> EvalResult<'tcx> {
149 let dest = self.eval_place(place)?;
151 use rustc::mir::Rvalue::*;
153 Use(ref operand) => {
154 // Avoid recomputing the layout
155 let op = self.eval_operand(operand, Some(dest.layout))?;
156 self.copy_op(op, dest)?;
159 BinaryOp(bin_op, ref left, ref right) => {
160 let layout = if binop_left_homogeneous(bin_op) { Some(dest.layout) } else { None };
161 let left = self.read_value(self.eval_operand(left, layout)?)?;
162 let layout = if binop_right_homogeneous(bin_op) { Some(left.layout) } else { None };
163 let right = self.read_value(self.eval_operand(right, layout)?)?;
164 self.binop_ignore_overflow(
172 CheckedBinaryOp(bin_op, ref left, ref right) => {
173 // Due to the extra boolean in the result, we can never reuse the `dest.layout`.
174 let left = self.read_value(self.eval_operand(left, None)?)?;
175 let layout = if binop_right_homogeneous(bin_op) { Some(left.layout) } else { None };
176 let right = self.read_value(self.eval_operand(right, layout)?)?;
177 self.binop_with_overflow(
185 UnaryOp(un_op, ref operand) => {
186 // The operand always has the same type as the result.
187 let val = self.read_value(self.eval_operand(operand, Some(dest.layout))?)?;
188 let val = self.unary_op(un_op, val.to_scalar()?, dest.layout)?;
189 self.write_scalar(val, dest)?;
192 Aggregate(ref kind, ref operands) => {
193 let (dest, active_field_index) = match **kind {
194 mir::AggregateKind::Adt(adt_def, variant_index, _, _, active_field_index) => {
195 self.write_discriminant_index(variant_index, dest)?;
196 if adt_def.is_enum() {
197 (self.place_downcast(dest, variant_index)?, active_field_index)
199 (dest, active_field_index)
205 for (i, operand) in operands.iter().enumerate() {
206 let op = self.eval_operand(operand, None)?;
207 // Ignore zero-sized fields.
208 if !op.layout.is_zst() {
209 let field_index = active_field_index.unwrap_or(i);
210 let field_dest = self.place_field(dest, field_index as u64)?;
211 self.copy_op(op, field_dest)?;
216 Repeat(ref operand, _) => {
217 let op = self.eval_operand(operand, None)?;
218 let dest = self.force_allocation(dest)?;
219 let length = dest.len(&self)?;
223 let first = self.mplace_field(dest, 0)?;
224 self.copy_op(op, first.into())?;
228 let (dest, dest_align) = first.to_scalar_ptr_align();
229 let rest = dest.ptr_offset(first.layout.size, &self)?;
230 self.memory.copy_repeatedly(
231 dest, dest_align, rest, dest_align, first.layout.size, length - 1, true
238 // FIXME(CTFE): don't allow computing the length of arrays in const eval
239 let src = self.eval_place(place)?;
240 let mplace = self.force_allocation(src)?;
241 let len = mplace.len(&self)?;
242 let size = self.pointer_size();
244 Scalar::from_uint(len, size),
249 Ref(_, _, ref place) => {
250 let src = self.eval_place(place)?;
251 let val = self.force_allocation(src)?.to_ref();
252 self.write_value(val, dest)?;
255 NullaryOp(mir::NullOp::Box, _) => {
256 M::box_alloc(self, dest)?;
259 NullaryOp(mir::NullOp::SizeOf, ty) => {
260 let ty = self.monomorphize(ty, self.substs());
261 let layout = self.layout_of(ty)?;
262 assert!(!layout.is_unsized(),
263 "SizeOf nullary MIR operator called for unsized type");
264 let size = self.pointer_size();
266 Scalar::from_uint(layout.size.bytes(), size),
271 Cast(kind, ref operand, cast_ty) => {
272 debug_assert_eq!(self.monomorphize(cast_ty, self.substs()), dest.layout.ty);
273 let src = self.eval_operand(operand, None)?;
274 self.cast(src, kind, dest)?;
277 Discriminant(ref place) => {
278 let place = self.eval_place(place)?;
279 let discr_val = self.read_discriminant(self.place_to_op(place)?)?.0;
280 let size = dest.layout.size;
281 self.write_scalar(Scalar::from_uint(discr_val, size), dest)?;
285 self.dump_place(*dest);
290 fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> EvalResult<'tcx> {
291 debug!("{:?}", terminator.kind);
292 self.tcx.span = terminator.source_info.span;
293 self.memory.tcx.span = terminator.source_info.span;
295 let old_stack = self.cur_frame();
296 let old_bb = self.frame().block;
297 self.eval_terminator(terminator)?;
298 if !self.stack.is_empty() {
299 // This should change *something*
300 debug_assert!(self.cur_frame() != old_stack || self.frame().block != old_bb);
301 debug!("// {:?}", self.frame().block);