rust/src/interpreter.rs

635 lines
24 KiB
Rust

use rustc::middle::const_eval;
use rustc::middle::def_id::DefId;
use rustc::middle::subst::{self, Subst, Substs};
use rustc::middle::ty::{self, TyCtxt};
use rustc::mir::mir_map::MirMap;
use rustc::mir::repr as mir;
use rustc::util::nodemap::DefIdMap;
use std::cell::RefCell;
use std::ops::Deref;
use std::rc::Rc;
use error::EvalResult;
use memory::{self, FieldRepr, Memory, Pointer, Repr};
use primval::{self, PrimVal};
const TRACE_EXECUTION: bool = true;
struct Interpreter<'a, 'tcx: 'a> {
/// The results of the type checker, from rustc.
tcx: &'a TyCtxt<'tcx>,
/// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
mir_map: &'a MirMap<'tcx>,
/// A local cache from DefIds to Mir for non-crate-local items.
mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
/// The virtual memory system.
memory: Memory,
/// The virtual call stack.
stack: Vec<Frame<'a, 'tcx>>,
/// Another stack containing the type substitutions for the current function invocation. It
/// exists separately from `stack` because it must contain the `Substs` for a function while
/// *creating* the `Frame` for that same function.
substs_stack: Vec<&'tcx Substs<'tcx>>,
}
/// A stack frame.
struct Frame<'a, 'tcx: 'a> {
/// The MIR for the function called on this frame.
mir: CachedMir<'a, 'tcx>,
/// The block this frame will execute when a function call returns back to this frame.
next_block: mir::BasicBlock,
/// A pointer for writing the return value of the current call if it's not a diverging call.
return_ptr: Option<Pointer>,
/// The list of locals for the current function, stored in order as
/// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
/// and the temporaries at `self.temp_offset`.
locals: Vec<Pointer>,
/// The offset of the first variable in `self.locals`.
var_offset: usize,
/// The offset of the first temporary in `self.locals`.
temp_offset: usize,
}
#[derive(Clone)]
enum CachedMir<'mir, 'tcx: 'mir> {
Ref(&'mir mir::Mir<'tcx>),
Owned(Rc<mir::Mir<'tcx>>)
}
/// Represents the action to be taken in the main loop as a result of executing a terminator.
enum TerminatorTarget {
/// Make a local jump to the given block.
Block(mir::BasicBlock),
/// Start executing from the new current frame. (For function calls.)
Call,
/// Stop executing the current frame and resume the previous frame.
Return,
}
impl<'a, 'tcx: 'a> Interpreter<'a, 'tcx> {
fn new(tcx: &'a TyCtxt<'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
Interpreter {
tcx: tcx,
mir_map: mir_map,
mir_cache: RefCell::new(DefIdMap()),
memory: Memory::new(),
stack: Vec::new(),
substs_stack: Vec::new(),
}
}
fn run(&mut self) -> EvalResult<()> {
use std::fmt::Debug;
fn print_trace<T: Debug>(t: &T, suffix: &'static str, indent: usize) {
if !TRACE_EXECUTION { return; }
for _ in 0..indent { print!(" "); }
println!("{:?}{}", t, suffix);
}
'outer: while !self.stack.is_empty() {
let mut current_block = self.current_frame().next_block;
loop {
print_trace(&current_block, ":", self.stack.len());
let current_mir = self.current_frame().mir.clone(); // Cloning a reference.
let block_data = current_mir.basic_block_data(current_block);
for stmt in &block_data.statements {
print_trace(stmt, "", self.stack.len() + 1);
let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
try!(self.eval_assignment(lvalue, rvalue));
}
let terminator = block_data.terminator();
print_trace(terminator, "", self.stack.len() + 1);
match try!(self.eval_terminator(terminator)) {
TerminatorTarget::Block(block) => current_block = block,
TerminatorTarget::Return => {
self.pop_stack_frame();
self.substs_stack.pop();
continue 'outer;
}
TerminatorTarget::Call => continue 'outer,
}
}
}
Ok(())
}
fn push_stack_frame(&mut self, mir: CachedMir<'a, 'tcx>, args: &[mir::Operand<'tcx>],
return_ptr: Option<Pointer>) -> EvalResult<()> {
let num_args = mir.arg_decls.len();
let num_vars = mir.var_decls.len();
let num_temps = mir.temp_decls.len();
assert_eq!(args.len(), num_args);
let mut locals = Vec::with_capacity(num_args + num_vars + num_temps);
for (arg_decl, arg_operand) in mir.arg_decls.iter().zip(args) {
let repr = self.ty_to_repr(arg_decl.ty);
let dest = self.memory.allocate(repr.size());
let src = try!(self.eval_operand(arg_operand));
try!(self.memory.copy(src, dest, repr.size()));
locals.push(dest);
}
let var_tys = mir.var_decls.iter().map(|v| v.ty);
let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
locals.extend(var_tys.chain(temp_tys).map(|ty| {
let repr = self.ty_to_repr(ty).size();
self.memory.allocate(repr)
}));
self.stack.push(Frame {
mir: mir.clone(),
next_block: mir::START_BLOCK,
return_ptr: return_ptr,
locals: locals,
var_offset: num_args,
temp_offset: num_args + num_vars,
});
Ok(())
}
fn pop_stack_frame(&mut self) {
let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
// TODO(tsion): Deallocate local variables.
}
fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
-> EvalResult<TerminatorTarget> {
use rustc::mir::repr::Terminator::*;
let target = match *terminator {
Return => TerminatorTarget::Return,
Goto { target } => TerminatorTarget::Block(target),
If { ref cond, targets: (then_target, else_target) } => {
let cond_ptr = try!(self.eval_operand(cond));
let cond_val = try!(self.memory.read_bool(cond_ptr));
TerminatorTarget::Block(if cond_val { then_target } else { else_target })
}
SwitchInt { ref discr, ref values, ref targets, .. } => {
let discr_ptr = try!(self.eval_lvalue(discr));
let discr_repr = self.lvalue_repr(discr);
let discr_val = try!(self.memory.read_primval(discr_ptr, &discr_repr));
// Branch to the `otherwise` case by default, if no match is found.
let mut target_block = targets[targets.len() - 1];
for (index, val_const) in values.iter().enumerate() {
let ptr = try!(self.const_to_ptr(val_const));
let val = try!(self.memory.read_primval(ptr, &discr_repr));
if discr_val == val {
target_block = targets[index];
break;
}
}
TerminatorTarget::Block(target_block)
}
Switch { ref discr, ref targets, .. } => {
let adt_ptr = try!(self.eval_lvalue(discr));
let adt_repr = self.lvalue_repr(discr);
let discr_repr = match adt_repr {
Repr::Sum { ref discr, .. } => discr,
_ => panic!("attmpted to switch on non-sum type"),
};
let discr_val = try!(self.memory.read_primval(adt_ptr, &discr_repr));
TerminatorTarget::Block(targets[discr_val.to_usize()])
}
Call { ref func, ref args, ref destination, .. } => {
let mut return_ptr = None;
if let Some((ref lv, target)) = *destination {
self.current_frame_mut().next_block = target;
return_ptr = Some(try!(self.eval_lvalue(lv)));
}
let func_ty = self.current_frame().mir.operand_ty(self.tcx, func);
match func_ty.sty {
ty::TyFnDef(def_id, substs, bare_fn_ty) => {
use syntax::abi::Abi;
match bare_fn_ty.abi {
Abi::RustIntrinsic => match &self.tcx.item_name(def_id).as_str()[..] {
"size_of" => {
let ty = *substs.types.get(subst::FnSpace, 0);
let ret_ptr = &mir::Lvalue::ReturnPointer;
let dest = try!(self.eval_lvalue(ret_ptr));
let dest_repr = self.lvalue_repr(ret_ptr);
let size = PrimVal::from_usize(self.ty_to_repr(ty).size(),
&dest_repr);
try!(self.memory.write_primval(dest, size));
// Since we pushed no stack frame, the main loop will act as if
// the call just completed and it's returning to the current
// frame.
TerminatorTarget::Call
},
name => panic!("can't handle intrinsic named {}", name),
},
Abi::Rust => {
let mir = self.load_mir(def_id);
let substs = self.tcx.mk_substs(
substs.subst(self.tcx, self.current_substs()));
self.substs_stack.push(substs);
try!(self.push_stack_frame(mir, args, return_ptr));
TerminatorTarget::Call
}
abi => panic!("can't handle function with ABI {:?}", abi),
}
}
_ => panic!("can't handle callee of type {:?}", func_ty),
}
}
Drop { target, .. } => {
// TODO: Handle destructors and dynamic drop.
TerminatorTarget::Block(target)
}
Resume => unimplemented!(),
};
Ok(target)
}
fn assign_to_product(&mut self, dest: Pointer, dest_repr: &Repr,
operands: &[mir::Operand<'tcx>]) -> EvalResult<()> {
match *dest_repr {
Repr::Product { ref fields, .. } => {
for (field, operand) in fields.iter().zip(operands) {
let src = try!(self.eval_operand(operand));
let field_dest = dest.offset(field.offset as isize);
try!(self.memory.copy(src, field_dest, field.repr.size()));
}
}
_ => panic!("expected Repr::Product target"),
}
Ok(())
}
fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
-> EvalResult<()>
{
let dest = try!(self.eval_lvalue(lvalue));
let dest_repr = self.lvalue_repr(lvalue);
use rustc::mir::repr::Rvalue::*;
match *rvalue {
Use(ref operand) => {
let src = try!(self.eval_operand(operand));
self.memory.copy(src, dest, dest_repr.size())
}
BinaryOp(bin_op, ref left, ref right) => {
let (left_ptr, left_repr) = try!(self.eval_operand_and_repr(left));
let (right_ptr, right_repr) = try!(self.eval_operand_and_repr(right));
let left_val = try!(self.memory.read_primval(left_ptr, &left_repr));
let right_val = try!(self.memory.read_primval(right_ptr, &right_repr));
self.memory.write_primval(dest, primval::binary_op(bin_op, left_val, right_val))
}
UnaryOp(un_op, ref operand) => {
let (ptr, repr) = try!(self.eval_operand_and_repr(operand));
let val = try!(self.memory.read_primval(ptr, &repr));
self.memory.write_primval(dest, primval::unary_op(un_op, val))
}
Aggregate(ref kind, ref operands) => {
use rustc::mir::repr::AggregateKind::*;
match *kind {
Tuple => self.assign_to_product(dest, &dest_repr, operands),
Adt(ref adt_def, variant_idx, _) => match adt_def.adt_kind() {
ty::AdtKind::Struct => self.assign_to_product(dest, &dest_repr, operands),
ty::AdtKind::Enum => match dest_repr {
Repr::Sum { ref discr, ref variants, .. } => {
if discr.size() > 0 {
let discr_val = PrimVal::from_usize(variant_idx, discr);
try!(self.memory.write_primval(dest, discr_val));
}
self.assign_to_product(
dest.offset(discr.size() as isize),
&variants[variant_idx],
operands
)
}
_ => panic!("expected Repr::Sum target"),
}
},
Vec => match dest_repr {
Repr::Array { ref elem, length } => {
assert_eq!(length, operands.len());
let elem_size = elem.size();
for (i, operand) in operands.iter().enumerate() {
let src = try!(self.eval_operand(operand));
let offset = i * elem_size;
let elem_dest = dest.offset(offset as isize);
try!(self.memory.copy(src, elem_dest, elem_size));
}
Ok(())
}
_ => panic!("expected Repr::Array target"),
},
Closure(..) => unimplemented!(),
}
}
Ref(_, _, ref lvalue) => {
let ptr = try!(self.eval_lvalue(lvalue));
self.memory.write_ptr(dest, ptr)
}
Box(ty) => {
let repr = self.ty_to_repr(ty);
let ptr = self.memory.allocate(repr.size());
self.memory.write_ptr(dest, ptr)
}
ref r => panic!("can't handle rvalue: {:?}", r),
}
}
fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
self.eval_operand_and_repr(op).map(|(p, _)| p)
}
fn eval_operand_and_repr(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<(Pointer, Repr)> {
use rustc::mir::repr::Operand::*;
match *op {
Consume(ref lvalue) => Ok((try!(self.eval_lvalue(lvalue)), self.lvalue_repr(lvalue))),
Constant(mir::Constant { ref literal, ty, .. }) => {
use rustc::mir::repr::Literal::*;
match *literal {
Value { ref value } => Ok((
try!(self.const_to_ptr(value)),
self.ty_to_repr(ty),
)),
ref l => panic!("can't handle item literal: {:?}", l),
}
}
}
}
fn lvalue_repr(&self, lvalue: &mir::Lvalue<'tcx>) -> Repr {
use rustc::mir::tcx::LvalueTy;
match self.current_frame().mir.lvalue_ty(self.tcx, lvalue) {
LvalueTy::Ty { ty } => self.ty_to_repr(ty),
LvalueTy::Downcast { ref adt_def, substs, variant_index } =>
self.make_variant_repr(&adt_def.variants[variant_index], substs),
}
}
fn eval_lvalue(&self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Pointer> {
let frame = self.current_frame();
use rustc::mir::repr::Lvalue::*;
let ptr = match *lvalue {
ReturnPointer =>
frame.return_ptr.expect("ReturnPointer used in a function with no return value"),
Arg(i) => frame.locals[i as usize],
Var(i) => frame.locals[frame.var_offset + i as usize],
Temp(i) => frame.locals[frame.temp_offset + i as usize],
Projection(ref proj) => {
let base_ptr = try!(self.eval_lvalue(&proj.base));
let base_repr = self.lvalue_repr(&proj.base);
use rustc::mir::repr::ProjectionElem::*;
match proj.elem {
Field(field, _) => match base_repr {
Repr::Product { ref fields, .. } =>
base_ptr.offset(fields[field.index()].offset as isize),
_ => panic!("field access on non-product type: {:?}", base_repr),
},
Downcast(..) => match base_repr {
Repr::Sum { ref discr, .. } => base_ptr.offset(discr.size() as isize),
_ => panic!("variant downcast on non-sum type"),
},
Deref => try!(self.memory.read_ptr(base_ptr)),
_ => unimplemented!(),
}
}
ref l => panic!("can't handle lvalue: {:?}", l),
};
Ok(ptr)
}
fn const_to_ptr(&mut self, const_val: &const_eval::ConstVal) -> EvalResult<Pointer> {
use rustc::middle::const_eval::ConstVal::*;
match *const_val {
Float(_f) => unimplemented!(),
Integral(int) => {
// TODO(tsion): Check int constant type.
let ptr = self.memory.allocate(8);
try!(self.memory.write_u64(ptr, int.to_u64_unchecked()));
Ok(ptr)
}
Str(ref _s) => unimplemented!(),
ByteStr(ref _bs) => unimplemented!(),
Bool(b) => {
let ptr = self.memory.allocate(Repr::Bool.size());
try!(self.memory.write_bool(ptr, b));
Ok(ptr)
}
Char(_c) => unimplemented!(),
Struct(_node_id) => unimplemented!(),
Tuple(_node_id) => unimplemented!(),
Function(_def_id) => unimplemented!(),
Array(_, _) => unimplemented!(),
Repeat(_, _) => unimplemented!(),
Dummy => unimplemented!(),
}
}
fn make_product_repr<I>(&self, iter: I) -> Repr where I: IntoIterator<Item = ty::Ty<'tcx>> {
let mut size = 0;
let fields = iter.into_iter().map(|ty| {
let repr = self.ty_to_repr(ty);
let old_size = size;
size += repr.size();
FieldRepr { offset: old_size, repr: repr }
}).collect();
Repr::Product { size: size, fields: fields }
}
fn make_variant_repr(&self, v: ty::VariantDef<'tcx>, substs: &'tcx Substs<'tcx>) -> Repr {
let field_tys = v.fields.iter().map(|f| f.ty(self.tcx, substs));
self.make_product_repr(field_tys)
}
// TODO(tsion): Cache these outputs.
fn ty_to_repr(&self, ty: ty::Ty<'tcx>) -> Repr {
use syntax::ast::{IntTy, UintTy};
match ty.subst(self.tcx, self.current_substs()).sty {
ty::TyBool => Repr::Bool,
ty::TyInt(IntTy::Is) => Repr::isize(),
ty::TyInt(IntTy::I8) => Repr::I8,
ty::TyInt(IntTy::I16) => Repr::I16,
ty::TyInt(IntTy::I32) => Repr::I32,
ty::TyInt(IntTy::I64) => Repr::I64,
ty::TyUint(UintTy::Us) => Repr::usize(),
ty::TyUint(UintTy::U8) => Repr::U8,
ty::TyUint(UintTy::U16) => Repr::U16,
ty::TyUint(UintTy::U32) => Repr::U32,
ty::TyUint(UintTy::U64) => Repr::U64,
ty::TyTuple(ref fields) => self.make_product_repr(fields.iter().cloned()),
ty::TyEnum(adt_def, substs) => {
let num_variants = adt_def.variants.len();
let discr = if num_variants <= 1 {
Repr::Product { size: 0, fields: vec![] }
} else if num_variants <= 1 << 8 {
Repr::U8
} else if num_variants <= 1 << 16 {
Repr::U16
} else if num_variants <= 1 << 32 {
Repr::U32
} else {
Repr::U64
};
let variants: Vec<Repr> = adt_def.variants.iter().map(|v| {
self.make_variant_repr(v, substs)
}).collect();
Repr::Sum {
discr: Box::new(discr),
max_variant_size: variants.iter().map(Repr::size).max().unwrap_or(0),
variants: variants,
}
}
ty::TyStruct(adt_def, substs) => {
assert_eq!(adt_def.variants.len(), 1);
self.make_variant_repr(&adt_def.variants[0], substs)
}
ty::TyArray(ref elem_ty, length) => Repr::Array {
elem: Box::new(self.ty_to_repr(elem_ty)),
length: length,
},
ty::TyRef(_, ty::TypeAndMut { ty, .. }) | ty::TyBox(ty) => Repr::Pointer {
target: Box::new(self.ty_to_repr(ty))
},
ref t => panic!("can't convert type to repr: {:?}", t),
}
}
fn current_frame(&self) -> &Frame<'a, 'tcx> {
self.stack.last().expect("no call frames exist")
}
fn current_frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
self.stack.last_mut().expect("no call frames exist")
}
fn current_substs(&self) -> &'tcx Substs<'tcx> {
self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
}
fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
match self.tcx.map.as_local_node_id(def_id) {
Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
None => {
let mut mir_cache = self.mir_cache.borrow_mut();
if let Some(mir) = mir_cache.get(&def_id) {
return CachedMir::Owned(mir.clone());
}
use rustc::middle::cstore::CrateStore;
let cs = &self.tcx.sess.cstore;
let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap();
let cached = Rc::new(mir);
mir_cache.insert(def_id, cached.clone());
CachedMir::Owned(cached)
}
}
}
}
impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
type Target = mir::Mir<'tcx>;
fn deref(&self) -> &mir::Mir<'tcx> {
match *self {
CachedMir::Ref(r) => r,
CachedMir::Owned(ref rc) => &rc,
}
}
}
pub fn interpret_start_points<'tcx>(tcx: &TyCtxt<'tcx>, mir_map: &MirMap<'tcx>) {
/// Print the given allocation and all allocations it depends on.
fn print_allocation_tree(memory: &Memory, alloc_id: memory::AllocId) {
let alloc = memory.get(alloc_id).unwrap();
println!(" {:?}: {:?}", alloc_id, alloc);
for &target_alloc in alloc.relocations.values() {
print_allocation_tree(memory, target_alloc);
}
}
for (&id, mir) in &mir_map.map {
for attr in tcx.map.attrs(id) {
use syntax::attr::AttrMetaMethods;
if attr.check_name("miri_run") {
let item = tcx.map.expect_item(id);
println!("Interpreting: {}", item.name);
let mut miri = Interpreter::new(tcx, mir_map);
let return_ptr = match mir.return_ty {
ty::FnConverging(ty) => {
let repr = miri.ty_to_repr(ty).size();
Some(miri.memory.allocate(repr))
}
ty::FnDiverging => None,
};
miri.push_stack_frame(CachedMir::Ref(mir), &[], return_ptr).unwrap();
miri.run().unwrap();
if let Some(ret) = return_ptr {
println!("Result:");
print_allocation_tree(&miri.memory, ret.alloc_id);
println!("");
}
}
}
}
}