rust/src/interpreter.rs

use rustc::middle::ty;
use rustc_mir::mir_map::MirMap;
use rustc_mir::repr::{self as mir, Mir};
use syntax::ast::Attribute;
use syntax::attr::AttrMetaMethods;

#[derive(Clone, Debug)]
enum Value {
    Uninit,
    Bool(bool),
    Int(i64), // FIXME: Should be bit-width aware.
}

struct Interpreter<'tcx> {
    mir: &'tcx Mir<'tcx>,
    var_vals: Vec<Value>,
    temp_vals: Vec<Value>,
    result: Value,
}

impl<'tcx> Interpreter<'tcx> {
    fn new(mir: &'tcx Mir<'tcx>) -> Self {
        Interpreter {
            mir: mir,
            var_vals: vec![Value::Uninit; mir.var_decls.len()],
            temp_vals: vec![Value::Uninit; mir.temp_decls.len()],
            result: Value::Uninit,
        }
    }

    fn run(&mut self) -> Value {
        let start_block = self.mir.basic_block_data(mir::START_BLOCK);

        for stmt in &start_block.statements {
            use rustc_mir::repr::Lvalue::*;
            use rustc_mir::repr::StatementKind::*;

            match stmt.kind {
                Assign(ref lv, ref rv) => {
                    let val = self.eval_rvalue(rv);

                    let spot = match *lv {
                        Var(i) => &mut self.var_vals[i as usize],
                        Temp(i) => &mut self.temp_vals[i as usize],
                        ReturnPointer => &mut self.result,
                        _ => unimplemented!(),
                    };

                    *spot = val;
                }
                Drop(_kind, ref _lv) => { /* TODO */ },
            }
        }

        self.result.clone()
    }

    fn eval_rvalue(&mut self, rvalue: &mir::Rvalue) -> Value {
        use rustc_mir::repr::Rvalue::*;
        use rustc_mir::repr::BinOp::*;
        use rustc_mir::repr::UnOp::*;

        match *rvalue {
            Use(ref operand) => self.eval_operand(operand),

            BinaryOp(bin_op, ref left, ref right) => {
                match (self.eval_operand(left), self.eval_operand(right)) {
                    (Value::Int(l), Value::Int(r)) => {
                        match bin_op {
                            Add => Value::Int(l + r),
                            Sub => Value::Int(l - r),
                            Mul => Value::Int(l * r),
                            Div => Value::Int(l / r),
                            Rem => Value::Int(l % r),
                            BitXor => Value::Int(l ^ r),
                            BitAnd => Value::Int(l & r),
                            BitOr => Value::Int(l | r),
                            Shl => Value::Int(l << r),
                            Shr => Value::Int(l >> r),
                            Eq => Value::Bool(l == r),
                            Lt => Value::Bool(l < r),
                            Le => Value::Bool(l <= r),
                            Ne => Value::Bool(l != r),
                            Ge => Value::Bool(l >= r),
                            Gt => Value::Bool(l > r),
                        }
                    }
                    _ => unimplemented!(),
                }
            }

            UnaryOp(un_op, ref operand) => {
                match (un_op, self.eval_operand(operand)) {
                    (Not, Value::Int(n)) => Value::Int(!n),
                    (Neg, Value::Int(n)) => Value::Int(-n),
                    _ => unimplemented!(),
                }
            }

            _ => unimplemented!(),
        }
    }

    fn eval_operand(&mut self, op: &mir::Operand) -> Value {
        use rustc::middle::const_eval::ConstVal::*;
        use rustc_mir::repr::Lvalue::*;
        use rustc_mir::repr::Operand::*;

        match *op {
            Consume(Var(i)) => self.var_vals[i as usize].clone(),
            Consume(Temp(i)) => self.temp_vals[i as usize].clone(),
            Constant(ref constant) => {
                match constant.literal {
                    mir::Literal::Value { value: Int(n) } => Value::Int(n),
                    _ => unimplemented!(),
                }
            }
            _ => unimplemented!(),
        }
    }
}

pub fn interpret_start_points<'tcx>(tcx: &ty::ctxt<'tcx>, mir_map: &MirMap<'tcx>) {
    for (&id, mir) in mir_map {
        for attr in tcx.map.attrs(id) {
            if attr.check_name("miri_run") {
                let item = tcx.map.expect_item(id);

                println!("Interpreting: {}", item.name);
                let mut interpreter = Interpreter::new(mir);
                let val = interpreter.run();
                let val_str = format!("{:?}", val);

                if !check_expected(&val_str, attr) {
                    println!("=> {}\n", val_str);
                }
            }
        }
    }
}

fn check_expected(actual: &str, attr: &Attribute) -> bool {
    if let Some(meta_items) = attr.meta_item_list() {
        for meta_item in meta_items {
            if meta_item.check_name("expected") {
                let expected = meta_item.value_str().unwrap();

                if actual == &expected[..] {
                    println!("Test passed!\n");
                } else {
                    println!("Actual value:\t{}\nExpected value:\t{}\n", actual, expected);
                }

                return true;
            }
        }
    }

    false
}