1939 lines
66 KiB
Rust
1939 lines
66 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*!
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* A classic liveness analysis based on dataflow over the AST. Computes,
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* for each local variable in a function, whether that variable is live
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* at a given point. Program execution points are identified by their
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* id.
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*
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* # Basic idea
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*
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* The basic model is that each local variable is assigned an index. We
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* represent sets of local variables using a vector indexed by this
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* index. The value in the vector is either 0, indicating the variable
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* is dead, or the id of an expression that uses the variable.
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*
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* We conceptually walk over the AST in reverse execution order. If we
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* find a use of a variable, we add it to the set of live variables. If
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* we find an assignment to a variable, we remove it from the set of live
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* variables. When we have to merge two flows, we take the union of
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* those two flows---if the variable is live on both paths, we simply
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* pick one id. In the event of loops, we continue doing this until a
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* fixed point is reached.
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*
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* ## Checking initialization
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*
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* At the function entry point, all variables must be dead. If this is
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* not the case, we can report an error using the id found in the set of
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* live variables, which identifies a use of the variable which is not
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* dominated by an assignment.
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*
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* ## Checking moves
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*
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* After each explicit move, the variable must be dead.
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*
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* ## Computing last uses
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*
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* Any use of the variable where the variable is dead afterwards is a
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* last use.
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*
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* # Implementation details
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*
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* The actual implementation contains two (nested) walks over the AST.
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* The outer walk has the job of building up the ir_maps instance for the
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* enclosing function. On the way down the tree, it identifies those AST
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* nodes and variable IDs that will be needed for the liveness analysis
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* and assigns them contiguous IDs. The liveness id for an AST node is
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* called a `live_node` (it's a newtype'd uint) and the id for a variable
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* is called a `variable` (another newtype'd uint).
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*
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* On the way back up the tree, as we are about to exit from a function
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* declaration we allocate a `liveness` instance. Now that we know
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* precisely how many nodes and variables we need, we can allocate all
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* the various arrays that we will need to precisely the right size. We then
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* perform the actual propagation on the `liveness` instance.
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*
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* This propagation is encoded in the various `propagate_through_*()`
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* methods. It effectively does a reverse walk of the AST; whenever we
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* reach a loop node, we iterate until a fixed point is reached.
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*
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* ## The `Users` struct
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*
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* At each live node `N`, we track three pieces of information for each
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* variable `V` (these are encapsulated in the `Users` struct):
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*
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* - `reader`: the `LiveNode` ID of some node which will read the value
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* that `V` holds on entry to `N`. Formally: a node `M` such
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* that there exists a path `P` from `N` to `M` where `P` does not
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* write `V`. If the `reader` is `invalid_node()`, then the current
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* value will never be read (the variable is dead, essentially).
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*
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* - `writer`: the `LiveNode` ID of some node which will write the
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* variable `V` and which is reachable from `N`. Formally: a node `M`
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* such that there exists a path `P` from `N` to `M` and `M` writes
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* `V`. If the `writer` is `invalid_node()`, then there is no writer
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* of `V` that follows `N`.
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*
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* - `used`: a boolean value indicating whether `V` is *used*. We
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* distinguish a *read* from a *use* in that a *use* is some read that
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* is not just used to generate a new value. For example, `x += 1` is
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* a read but not a use. This is used to generate better warnings.
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*
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* ## Special Variables
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*
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* We generate various special variables for various, well, special purposes.
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* These are described in the `specials` struct:
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*
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* - `exit_ln`: a live node that is generated to represent every 'exit' from
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* the function, whether it be by explicit return, fail, or other means.
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*
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* - `fallthrough_ln`: a live node that represents a fallthrough
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*
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* - `no_ret_var`: a synthetic variable that is only 'read' from, the
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* fallthrough node. This allows us to detect functions where we fail
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* to return explicitly.
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*/
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use core::prelude::*;
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use middle::pat_util;
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use middle::ty;
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use middle::typeck;
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use middle::moves;
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use util::ppaux::ty_to_str;
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use core::cmp;
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use core::dvec::DVec;
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use core::io::WriterUtil;
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use core::io;
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use core::ptr;
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use core::to_str;
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use core::uint;
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use core::vec;
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use std::oldmap::HashMap;
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use syntax::ast::*;
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use syntax::codemap::span;
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use syntax::parse::token::special_idents;
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use syntax::print::pprust::{expr_to_str, block_to_str};
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use syntax::visit::{fk_anon, fk_dtor, fk_fn_block, fk_item_fn, fk_method};
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use syntax::visit::{vt};
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use syntax::{visit, ast_util};
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// Maps from an expr id to a list of variable ids for which this expr
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// is the last use. Typically, the expr is a path and the node id is
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// the local/argument/etc that the path refers to. However, it also
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// possible for the expr to be a closure, in which case the list is a
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// list of closed over variables that can be moved into the closure.
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//
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// Very subtle (#2633): borrowck will remove entries from this table
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// if it detects an outstanding loan (that is, the addr is taken).
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pub type last_use_map = HashMap<node_id, @DVec<node_id>>;
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enum Variable = uint;
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enum LiveNode = uint;
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impl Variable : cmp::Eq {
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pure fn eq(&self, other: &Variable) -> bool { *(*self) == *(*other) }
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pure fn ne(&self, other: &Variable) -> bool { *(*self) != *(*other) }
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}
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impl LiveNode : cmp::Eq {
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pure fn eq(&self, other: &LiveNode) -> bool { *(*self) == *(*other) }
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pure fn ne(&self, other: &LiveNode) -> bool { *(*self) != *(*other) }
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}
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enum LiveNodeKind {
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FreeVarNode(span),
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ExprNode(span),
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VarDefNode(span),
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ExitNode
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}
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impl LiveNodeKind : cmp::Eq {
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pure fn eq(&self, other: &LiveNodeKind) -> bool {
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match (*self) {
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FreeVarNode(e0a) => {
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match (*other) {
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FreeVarNode(e0b) => e0a == e0b,
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_ => false
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}
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}
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ExprNode(e0a) => {
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match (*other) {
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ExprNode(e0b) => e0a == e0b,
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_ => false
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}
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}
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VarDefNode(e0a) => {
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match (*other) {
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VarDefNode(e0b) => e0a == e0b,
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_ => false
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}
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}
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ExitNode => {
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match (*other) {
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ExitNode => true,
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_ => false
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}
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}
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}
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}
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pure fn ne(&self, other: &LiveNodeKind) -> bool { !(*self).eq(other) }
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}
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fn live_node_kind_to_str(lnk: LiveNodeKind, cx: ty::ctxt) -> ~str {
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let cm = cx.sess.codemap;
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match lnk {
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FreeVarNode(s) => fmt!("Free var node [%s]", cm.span_to_str(s)),
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ExprNode(s) => fmt!("Expr node [%s]", cm.span_to_str(s)),
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VarDefNode(s) => fmt!("Var def node [%s]", cm.span_to_str(s)),
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ExitNode => ~"Exit node"
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}
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}
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pub fn check_crate(tcx: ty::ctxt,
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method_map: typeck::method_map,
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variable_moves_map: moves::VariableMovesMap,
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capture_map: moves::CaptureMap,
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crate: @crate) -> last_use_map {
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let visitor = visit::mk_vt(@visit::Visitor {
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visit_fn: visit_fn,
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visit_local: visit_local,
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visit_expr: visit_expr,
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visit_arm: visit_arm,
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.. *visit::default_visitor()
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});
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let last_use_map = HashMap();
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let initial_maps = @mut IrMaps(tcx,
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method_map,
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variable_moves_map,
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capture_map,
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last_use_map);
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visit::visit_crate(*crate, initial_maps, visitor);
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tcx.sess.abort_if_errors();
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return last_use_map;
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}
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impl LiveNode: to_str::ToStr {
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pure fn to_str(&self) -> ~str { fmt!("ln(%u)", **self) }
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}
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impl Variable: to_str::ToStr {
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pure fn to_str(&self) -> ~str { fmt!("v(%u)", **self) }
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}
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// ______________________________________________________________________
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// Creating ir_maps
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//
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// This is the first pass and the one that drives the main
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// computation. It walks up and down the IR once. On the way down,
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// we count for each function the number of variables as well as
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// liveness nodes. A liveness node is basically an expression or
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// capture clause that does something of interest: either it has
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// interesting control flow or it uses/defines a local variable.
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//
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// On the way back up, at each function node we create liveness sets
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// (we now know precisely how big to make our various vectors and so
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// forth) and then do the data-flow propagation to compute the set
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// of live variables at each program point.
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//
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// Finally, we run back over the IR one last time and, using the
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// computed liveness, check various safety conditions. For example,
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// there must be no live nodes at the definition site for a variable
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// unless it has an initializer. Similarly, each non-mutable local
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// variable must not be assigned if there is some successor
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// assignment. And so forth.
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impl LiveNode {
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pure fn is_valid() -> bool { *self != uint::max_value }
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}
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fn invalid_node() -> LiveNode { LiveNode(uint::max_value) }
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struct CaptureInfo {
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ln: LiveNode,
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is_move: bool,
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var_nid: node_id
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}
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enum LocalKind {
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FromMatch(binding_mode),
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FromLetWithInitializer,
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FromLetNoInitializer
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}
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struct LocalInfo {
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id: node_id,
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ident: ident,
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is_mutbl: bool,
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kind: LocalKind,
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}
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enum VarKind {
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Arg(node_id, ident, rmode),
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Local(LocalInfo),
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ImplicitRet
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}
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fn relevant_def(def: def) -> Option<node_id> {
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match def {
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def_binding(nid, _) |
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def_arg(nid, _, _) |
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def_local(nid, _) |
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def_self(nid, _) => Some(nid),
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_ => None
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}
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}
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struct IrMaps {
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tcx: ty::ctxt,
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method_map: typeck::method_map,
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variable_moves_map: moves::VariableMovesMap,
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capture_map: moves::CaptureMap,
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last_use_map: last_use_map,
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num_live_nodes: uint,
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num_vars: uint,
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live_node_map: HashMap<node_id, LiveNode>,
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variable_map: HashMap<node_id, Variable>,
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capture_info_map: HashMap<node_id, @~[CaptureInfo]>,
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var_kinds: ~[VarKind],
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lnks: ~[LiveNodeKind],
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}
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fn IrMaps(tcx: ty::ctxt,
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method_map: typeck::method_map,
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variable_moves_map: moves::VariableMovesMap,
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capture_map: moves::CaptureMap,
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last_use_map: last_use_map)
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-> IrMaps {
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IrMaps {
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tcx: tcx,
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method_map: method_map,
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variable_moves_map: variable_moves_map,
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capture_map: capture_map,
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last_use_map: last_use_map,
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num_live_nodes: 0,
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num_vars: 0,
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live_node_map: HashMap(),
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variable_map: HashMap(),
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capture_info_map: HashMap(),
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var_kinds: ~[],
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lnks: ~[]
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}
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}
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impl IrMaps {
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fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode {
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let ln = LiveNode(self.num_live_nodes);
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self.lnks.push(lnk);
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self.num_live_nodes += 1;
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debug!("%s is of kind %s", ln.to_str(),
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live_node_kind_to_str(lnk, self.tcx));
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ln
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}
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fn add_live_node_for_node(&mut self,
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node_id: node_id,
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lnk: LiveNodeKind) {
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let ln = self.add_live_node(lnk);
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self.live_node_map.insert(node_id, ln);
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debug!("%s is node %d", ln.to_str(), node_id);
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}
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fn add_variable(&mut self, vk: VarKind) -> Variable {
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let v = Variable(self.num_vars);
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self.var_kinds.push(vk);
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self.num_vars += 1;
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match vk {
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Local(LocalInfo {id:node_id, _}) |
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Arg(node_id, _, _) => {
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self.variable_map.insert(node_id, v);
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}
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ImplicitRet => {}
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}
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debug!("%s is %?", v.to_str(), vk);
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v
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}
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fn variable(&mut self, node_id: node_id, span: span) -> Variable {
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match self.variable_map.find(&node_id) {
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Some(var) => var,
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None => {
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self.tcx.sess.span_bug(
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span, fmt!("No variable registered for id %d", node_id));
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}
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}
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}
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fn variable_name(&mut self, var: Variable) -> ~str {
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match copy self.var_kinds[*var] {
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Local(LocalInfo {ident: nm, _}) |
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Arg(_, nm, _) => self.tcx.sess.str_of(nm),
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ImplicitRet => ~"<implicit-ret>"
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}
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}
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fn set_captures(&mut self, node_id: node_id, +cs: ~[CaptureInfo]) {
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self.capture_info_map.insert(node_id, @cs);
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}
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fn captures(&mut self, expr: @expr) -> @~[CaptureInfo] {
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match self.capture_info_map.find(&expr.id) {
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Some(caps) => caps,
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None => {
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self.tcx.sess.span_bug(expr.span, ~"no registered caps");
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}
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}
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}
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fn lnk(&mut self, ln: LiveNode) -> LiveNodeKind {
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self.lnks[*ln]
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}
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fn add_last_use(&mut self, expr_id: node_id, var: Variable) {
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let vk = self.var_kinds[*var];
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debug!("Node %d is a last use of variable %?", expr_id, vk);
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match vk {
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Arg(id, _, by_copy) |
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Local(LocalInfo {id: id, kind: FromLetNoInitializer, _}) |
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Local(LocalInfo {id: id, kind: FromLetWithInitializer, _}) |
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Local(LocalInfo {id: id, kind: FromMatch(_), _}) => {
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let v = match self.last_use_map.find(&expr_id) {
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Some(v) => v,
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None => {
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let v = @DVec();
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self.last_use_map.insert(expr_id, v);
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v
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}
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};
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(*v).push(id);
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}
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Arg(_, _, by_ref) |
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Arg(_, _, by_val) | ImplicitRet => {
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debug!("--but it is not owned");
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}
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}
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}
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}
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fn visit_fn(fk: visit::fn_kind,
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decl: fn_decl,
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body: blk,
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sp: span,
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id: node_id,
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&&self: @mut IrMaps,
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v: vt<@mut IrMaps>) {
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debug!("visit_fn: id=%d", id);
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let _i = ::util::common::indenter();
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// swap in a new set of IR maps for this function body:
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let fn_maps = @mut IrMaps(self.tcx,
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self.method_map,
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self.variable_moves_map,
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self.capture_map,
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self.last_use_map);
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debug!("creating fn_maps: %x", ptr::addr_of(&(*fn_maps)) as uint);
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for decl.inputs.each |arg| {
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let mode = ty::resolved_mode(self.tcx, arg.mode);
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do pat_util::pat_bindings(self.tcx.def_map, arg.pat)
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|_bm, arg_id, _x, path| {
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debug!("adding argument %d", arg_id);
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let ident = ast_util::path_to_ident(path);
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fn_maps.add_variable(Arg(arg_id, ident, mode));
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}
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};
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// Add `self`, whether explicit or implicit.
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match fk {
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fk_method(_, _, method) => {
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match method.self_ty.node {
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sty_by_ref => {
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fn_maps.add_variable(Arg(method.self_id,
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special_idents::self_,
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by_ref));
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}
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sty_value | sty_region(_) | sty_box(_) | sty_uniq(_) => {
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fn_maps.add_variable(Arg(method.self_id,
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special_idents::self_,
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by_copy));
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}
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sty_static => {}
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}
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}
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fk_dtor(_, _, self_id, _) => {
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fn_maps.add_variable(Arg(self_id,
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special_idents::self_,
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by_copy));
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}
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fk_item_fn(*) | fk_anon(*) | fk_fn_block(*) => {}
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}
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// gather up the various local variables, significant expressions,
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// and so forth:
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visit::visit_fn(fk, decl, body, sp, id, fn_maps, v);
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// Special nodes and variables:
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|
// - exit_ln represents the end of the fn, either by return or fail
|
|
// - implicit_ret_var is a pseudo-variable that represents
|
|
// an implicit return
|
|
let specials = Specials {
|
|
exit_ln: fn_maps.add_live_node(ExitNode),
|
|
fallthrough_ln: fn_maps.add_live_node(ExitNode),
|
|
no_ret_var: fn_maps.add_variable(ImplicitRet)
|
|
};
|
|
|
|
// compute liveness
|
|
let lsets = @Liveness(fn_maps, specials);
|
|
let entry_ln = (*lsets).compute(decl, body);
|
|
|
|
// check for various error conditions
|
|
let check_vt = visit::mk_vt(@visit::Visitor {
|
|
visit_fn: check_fn,
|
|
visit_local: check_local,
|
|
visit_expr: check_expr,
|
|
visit_arm: check_arm,
|
|
.. *visit::default_visitor()
|
|
});
|
|
(check_vt.visit_block)(body, lsets, check_vt);
|
|
lsets.check_ret(id, sp, fk, entry_ln);
|
|
lsets.warn_about_unused_args(decl, entry_ln);
|
|
}
|
|
|
|
fn visit_local(local: @local, &&self: @mut IrMaps, vt: vt<@mut IrMaps>) {
|
|
let def_map = self.tcx.def_map;
|
|
do pat_util::pat_bindings(def_map, local.node.pat) |_bm, p_id, sp, path| {
|
|
debug!("adding local variable %d", p_id);
|
|
let name = ast_util::path_to_ident(path);
|
|
self.add_live_node_for_node(p_id, VarDefNode(sp));
|
|
let kind = match local.node.init {
|
|
Some(_) => FromLetWithInitializer,
|
|
None => FromLetNoInitializer
|
|
};
|
|
self.add_variable(Local(LocalInfo {
|
|
id: p_id,
|
|
ident: name,
|
|
is_mutbl: local.node.is_mutbl,
|
|
kind: kind
|
|
}));
|
|
}
|
|
visit::visit_local(local, self, vt);
|
|
}
|
|
|
|
fn visit_arm(arm: arm, &&self: @mut IrMaps, vt: vt<@mut IrMaps>) {
|
|
let def_map = self.tcx.def_map;
|
|
for arm.pats.each |pat| {
|
|
do pat_util::pat_bindings(def_map, *pat) |bm, p_id, sp, path| {
|
|
debug!("adding local variable %d from match with bm %?",
|
|
p_id, bm);
|
|
let name = ast_util::path_to_ident(path);
|
|
self.add_live_node_for_node(p_id, VarDefNode(sp));
|
|
self.add_variable(Local(LocalInfo {
|
|
id: p_id,
|
|
ident: name,
|
|
is_mutbl: false,
|
|
kind: FromMatch(bm)
|
|
}));
|
|
}
|
|
}
|
|
visit::visit_arm(arm, self, vt);
|
|
}
|
|
|
|
fn visit_expr(expr: @expr, &&self: @mut IrMaps, vt: vt<@mut IrMaps>) {
|
|
match expr.node {
|
|
// live nodes required for uses or definitions of variables:
|
|
expr_path(_) => {
|
|
let def = self.tcx.def_map.get(&expr.id);
|
|
debug!("expr %d: path that leads to %?", expr.id, def);
|
|
if relevant_def(def).is_some() {
|
|
self.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
}
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
expr_fn(*) |
|
|
expr_fn_block(*) => {
|
|
// Interesting control flow (for loops can contain labeled
|
|
// breaks or continues)
|
|
self.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
|
|
// Make a live_node for each captured variable, with the span
|
|
// being the location that the variable is used. This results
|
|
// in better error messages than just pointing at the closure
|
|
// construction site.
|
|
let cvs = self.capture_map.get(&expr.id);
|
|
let mut call_caps = ~[];
|
|
for cvs.each |cv| {
|
|
match relevant_def(cv.def) {
|
|
Some(rv) => {
|
|
let cv_ln = self.add_live_node(FreeVarNode(cv.span));
|
|
let is_move = match cv.mode {
|
|
// var must be dead afterwards
|
|
moves::CapMove => true,
|
|
|
|
// var can stil be used
|
|
moves::CapCopy | moves::CapRef => false
|
|
};
|
|
call_caps.push(CaptureInfo {ln: cv_ln,
|
|
is_move: is_move,
|
|
var_nid: rv});
|
|
}
|
|
None => {}
|
|
}
|
|
}
|
|
self.set_captures(expr.id, call_caps);
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
// live nodes required for interesting control flow:
|
|
expr_if(*) | expr_match(*) | expr_while(*) | expr_loop(*) => {
|
|
self.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
expr_binary(op, _, _) if ast_util::lazy_binop(op) => {
|
|
self.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
// otherwise, live nodes are not required:
|
|
expr_index(*) | expr_field(*) | expr_vstore(*) |
|
|
expr_vec(*) | expr_rec(*) | expr_call(*) | expr_method_call(*) |
|
|
expr_tup(*) | expr_log(*) | expr_binary(*) |
|
|
expr_assert(*) | expr_addr_of(*) | expr_copy(*) |
|
|
expr_loop_body(*) | expr_do_body(*) | expr_cast(*) |
|
|
expr_unary(*) |
|
|
expr_break(_) | expr_again(_) | expr_lit(_) | expr_ret(*) |
|
|
expr_block(*) | expr_assign(*) |
|
|
expr_swap(*) | expr_assign_op(*) | expr_mac(*) | expr_struct(*) |
|
|
expr_repeat(*) | expr_paren(*) => {
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
}
|
|
}
|
|
|
|
// ______________________________________________________________________
|
|
// Computing liveness sets
|
|
//
|
|
// Actually we compute just a bit more than just liveness, but we use
|
|
// the same basic propagation framework in all cases.
|
|
|
|
struct Users {
|
|
reader: LiveNode,
|
|
writer: LiveNode,
|
|
used: bool
|
|
}
|
|
|
|
fn invalid_users() -> Users {
|
|
Users {
|
|
reader: invalid_node(),
|
|
writer: invalid_node(),
|
|
used: false
|
|
}
|
|
}
|
|
|
|
struct Specials {
|
|
exit_ln: LiveNode,
|
|
fallthrough_ln: LiveNode,
|
|
no_ret_var: Variable
|
|
}
|
|
|
|
const ACC_READ: uint = 1u;
|
|
const ACC_WRITE: uint = 2u;
|
|
const ACC_USE: uint = 4u;
|
|
|
|
type LiveNodeMap = HashMap<node_id, LiveNode>;
|
|
|
|
struct Liveness {
|
|
tcx: ty::ctxt,
|
|
ir: @mut IrMaps,
|
|
s: Specials,
|
|
successors: ~[mut LiveNode],
|
|
users: ~[mut Users],
|
|
// The list of node IDs for the nested loop scopes
|
|
// we're in.
|
|
loop_scope: DVec<node_id>,
|
|
// mappings from loop node ID to LiveNode
|
|
// ("break" label should map to loop node ID,
|
|
// it probably doesn't now)
|
|
break_ln: LiveNodeMap,
|
|
cont_ln: LiveNodeMap
|
|
}
|
|
|
|
fn Liveness(ir: @mut IrMaps, specials: Specials) -> Liveness {
|
|
Liveness {
|
|
ir: ir,
|
|
tcx: ir.tcx,
|
|
s: specials,
|
|
successors:
|
|
vec::cast_to_mut(
|
|
vec::from_elem(ir.num_live_nodes,
|
|
invalid_node())),
|
|
users:
|
|
vec::cast_to_mut(
|
|
vec::from_elem(ir.num_live_nodes * ir.num_vars,
|
|
invalid_users())),
|
|
loop_scope: DVec(),
|
|
break_ln: HashMap(),
|
|
cont_ln: HashMap()
|
|
}
|
|
}
|
|
|
|
impl Liveness {
|
|
fn live_node(node_id: node_id, span: span) -> LiveNode {
|
|
match self.ir.live_node_map.find(&node_id) {
|
|
Some(ln) => ln,
|
|
None => {
|
|
// This must be a mismatch between the ir_map construction
|
|
// above and the propagation code below; the two sets of
|
|
// code have to agree about which AST nodes are worth
|
|
// creating liveness nodes for.
|
|
self.tcx.sess.span_bug(
|
|
span, fmt!("No live node registered for node %d",
|
|
node_id));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn variable_from_path(expr: @expr) -> Option<Variable> {
|
|
match expr.node {
|
|
expr_path(_) => {
|
|
let def = self.tcx.def_map.get(&expr.id);
|
|
relevant_def(def).map(
|
|
|rdef| self.variable(*rdef, expr.span)
|
|
)
|
|
}
|
|
_ => None
|
|
}
|
|
}
|
|
|
|
fn variable(node_id: node_id, span: span) -> Variable {
|
|
self.ir.variable(node_id, span)
|
|
}
|
|
|
|
fn variable_from_def_map(node_id: node_id,
|
|
span: span) -> Option<Variable> {
|
|
match self.tcx.def_map.find(&node_id) {
|
|
Some(def) => {
|
|
relevant_def(def).map(
|
|
|rdef| self.variable(*rdef, span)
|
|
)
|
|
}
|
|
None => {
|
|
self.tcx.sess.span_bug(
|
|
span, ~"Not present in def map")
|
|
}
|
|
}
|
|
}
|
|
|
|
fn pat_bindings(pat: @pat, f: fn(LiveNode, Variable, span)) {
|
|
let def_map = self.tcx.def_map;
|
|
do pat_util::pat_bindings(def_map, pat) |_bm, p_id, sp, _n| {
|
|
let ln = self.live_node(p_id, sp);
|
|
let var = self.variable(p_id, sp);
|
|
f(ln, var, sp);
|
|
}
|
|
}
|
|
|
|
fn arm_pats_bindings(pats: &[@pat], f: fn(LiveNode, Variable, span)) {
|
|
// only consider the first pattern; any later patterns must have
|
|
// the same bindings, and we also consider the first pattern to be
|
|
// the "authoratative" set of ids
|
|
if !pats.is_empty() {
|
|
self.pat_bindings(pats[0], f)
|
|
}
|
|
}
|
|
|
|
fn define_bindings_in_pat(pat: @pat, succ: LiveNode) -> LiveNode {
|
|
self.define_bindings_in_arm_pats([pat], succ)
|
|
}
|
|
|
|
fn define_bindings_in_arm_pats(pats: &[@pat],
|
|
succ: LiveNode) -> LiveNode {
|
|
let mut succ = succ;
|
|
do self.arm_pats_bindings(pats) |ln, var, _sp| {
|
|
self.init_from_succ(ln, succ);
|
|
self.define(ln, var);
|
|
succ = ln;
|
|
}
|
|
succ
|
|
}
|
|
|
|
fn idx(ln: LiveNode, var: Variable) -> uint {
|
|
*ln * self.ir.num_vars + *var
|
|
}
|
|
|
|
fn live_on_entry(ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
|
|
assert ln.is_valid();
|
|
let reader = self.users[self.idx(ln, var)].reader;
|
|
if reader.is_valid() {Some(self.ir.lnk(reader))} else {None}
|
|
}
|
|
|
|
/*
|
|
Is this variable live on entry to any of its successor nodes?
|
|
*/
|
|
fn live_on_exit(ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
|
|
self.live_on_entry(copy self.successors[*ln], var)
|
|
}
|
|
|
|
fn used_on_entry(ln: LiveNode, var: Variable) -> bool {
|
|
assert ln.is_valid();
|
|
self.users[self.idx(ln, var)].used
|
|
}
|
|
|
|
fn assigned_on_entry(ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
|
|
assert ln.is_valid();
|
|
let writer = self.users[self.idx(ln, var)].writer;
|
|
if writer.is_valid() {Some(self.ir.lnk(writer))} else {None}
|
|
}
|
|
|
|
fn assigned_on_exit(ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
|
|
self.assigned_on_entry(copy self.successors[*ln], var)
|
|
}
|
|
|
|
fn indices(ln: LiveNode, op: fn(uint)) {
|
|
let node_base_idx = self.idx(ln, Variable(0));
|
|
for uint::range(0, self.ir.num_vars) |var_idx| {
|
|
op(node_base_idx + var_idx)
|
|
}
|
|
}
|
|
|
|
fn indices2(ln: LiveNode, succ_ln: LiveNode,
|
|
op: fn(uint, uint)) {
|
|
let node_base_idx = self.idx(ln, Variable(0u));
|
|
let succ_base_idx = self.idx(succ_ln, Variable(0u));
|
|
for uint::range(0u, self.ir.num_vars) |var_idx| {
|
|
op(node_base_idx + var_idx, succ_base_idx + var_idx);
|
|
}
|
|
}
|
|
|
|
fn write_vars(wr: io::Writer,
|
|
ln: LiveNode,
|
|
test: fn(uint) -> LiveNode) {
|
|
let node_base_idx = self.idx(ln, Variable(0));
|
|
for uint::range(0, self.ir.num_vars) |var_idx| {
|
|
let idx = node_base_idx + var_idx;
|
|
if test(idx).is_valid() {
|
|
wr.write_str(~" ");
|
|
wr.write_str(Variable(var_idx).to_str());
|
|
}
|
|
}
|
|
}
|
|
|
|
fn find_loop_scope(opt_label: Option<ident>, id: node_id, sp: span)
|
|
-> node_id {
|
|
match opt_label {
|
|
Some(_) => // Refers to a labeled loop. Use the results of resolve
|
|
// to find with one
|
|
match self.tcx.def_map.find(&id) {
|
|
Some(def_label(loop_id)) => loop_id,
|
|
_ => self.tcx.sess.span_bug(sp, ~"Label on break/loop \
|
|
doesn't refer to a loop")
|
|
},
|
|
None =>
|
|
// Vanilla 'break' or 'loop', so use the enclosing
|
|
// loop scope
|
|
if self.loop_scope.len() == 0 {
|
|
self.tcx.sess.span_bug(sp, ~"break outside loop");
|
|
}
|
|
else {
|
|
self.loop_scope.last()
|
|
}
|
|
}
|
|
}
|
|
|
|
fn ln_str(ln: LiveNode) -> ~str {
|
|
do io::with_str_writer |wr| {
|
|
wr.write_str(~"[ln(");
|
|
wr.write_uint(*ln);
|
|
wr.write_str(~") of kind ");
|
|
wr.write_str(fmt!("%?", copy self.ir.lnks[*ln]));
|
|
wr.write_str(~" reads");
|
|
self.write_vars(wr, ln, |idx| self.users[idx].reader );
|
|
wr.write_str(~" writes");
|
|
self.write_vars(wr, ln, |idx| self.users[idx].writer );
|
|
wr.write_str(~" ");
|
|
wr.write_str(~" precedes ");
|
|
wr.write_str((copy self.successors[*ln]).to_str());
|
|
wr.write_str(~"]");
|
|
}
|
|
}
|
|
|
|
fn init_empty(ln: LiveNode, succ_ln: LiveNode) {
|
|
self.successors[*ln] = succ_ln;
|
|
|
|
// It is not necessary to initialize the
|
|
// values to empty because this is the value
|
|
// they have when they are created, and the sets
|
|
// only grow during iterations.
|
|
//
|
|
// self.indices(ln) { |idx|
|
|
// self.users[idx] = invalid_users();
|
|
// }
|
|
}
|
|
|
|
fn init_from_succ(ln: LiveNode, succ_ln: LiveNode) {
|
|
// more efficient version of init_empty() / merge_from_succ()
|
|
self.successors[*ln] = succ_ln;
|
|
self.indices2(ln, succ_ln, |idx, succ_idx| {
|
|
self.users[idx] = self.users[succ_idx]
|
|
});
|
|
debug!("init_from_succ(ln=%s, succ=%s)",
|
|
self.ln_str(ln), self.ln_str(succ_ln));
|
|
}
|
|
|
|
fn merge_from_succ(ln: LiveNode, succ_ln: LiveNode,
|
|
first_merge: bool) -> bool {
|
|
if ln == succ_ln { return false; }
|
|
|
|
let mut changed = false;
|
|
do self.indices2(ln, succ_ln) |idx, succ_idx| {
|
|
changed |= copy_if_invalid(copy self.users[succ_idx].reader,
|
|
&mut self.users[idx].reader);
|
|
changed |= copy_if_invalid(copy self.users[succ_idx].writer,
|
|
&mut self.users[idx].writer);
|
|
if self.users[succ_idx].used && !self.users[idx].used {
|
|
self.users[idx].used = true;
|
|
changed = true;
|
|
}
|
|
}
|
|
|
|
debug!("merge_from_succ(ln=%s, succ=%s, first_merge=%b, changed=%b)",
|
|
ln.to_str(), self.ln_str(succ_ln), first_merge, changed);
|
|
return changed;
|
|
|
|
fn copy_if_invalid(src: LiveNode, dst: &mut LiveNode) -> bool {
|
|
if src.is_valid() {
|
|
if !dst.is_valid() {
|
|
*dst = src;
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Indicates that a local variable was *defined*; we know that no
|
|
// uses of the variable can precede the definition (resolve checks
|
|
// this) so we just clear out all the data.
|
|
fn define(writer: LiveNode, var: Variable) {
|
|
let idx = self.idx(writer, var);
|
|
self.users[idx].reader = invalid_node();
|
|
self.users[idx].writer = invalid_node();
|
|
|
|
debug!("%s defines %s (idx=%u): %s", writer.to_str(), var.to_str(),
|
|
idx, self.ln_str(writer));
|
|
}
|
|
|
|
// Either read, write, or both depending on the acc bitset
|
|
fn acc(ln: LiveNode, var: Variable, acc: uint) {
|
|
let idx = self.idx(ln, var);
|
|
let user = &mut self.users[idx];
|
|
|
|
if (acc & ACC_WRITE) != 0 {
|
|
user.reader = invalid_node();
|
|
user.writer = ln;
|
|
}
|
|
|
|
// Important: if we both read/write, must do read second
|
|
// or else the write will override.
|
|
if (acc & ACC_READ) != 0 {
|
|
user.reader = ln;
|
|
}
|
|
|
|
if (acc & ACC_USE) != 0 {
|
|
self.users[idx].used = true;
|
|
}
|
|
|
|
debug!("%s accesses[%x] %s: %s",
|
|
ln.to_str(), acc, var.to_str(), self.ln_str(ln));
|
|
}
|
|
|
|
// _______________________________________________________________________
|
|
|
|
fn compute(decl: fn_decl, body: blk) -> LiveNode {
|
|
// if there is a `break` or `again` at the top level, then it's
|
|
// effectively a return---this only occurs in `for` loops,
|
|
// where the body is really a closure.
|
|
|
|
debug!("compute: using id for block, %s", block_to_str(body,
|
|
self.tcx.sess.intr()));
|
|
|
|
let entry_ln: LiveNode =
|
|
self.with_loop_nodes(body.node.id, self.s.exit_ln, self.s.exit_ln,
|
|
|| { self.propagate_through_fn_block(decl, body) });
|
|
|
|
// hack to skip the loop unless debug! is enabled:
|
|
debug!("^^ liveness computation results for body %d (entry=%s)",
|
|
{
|
|
for uint::range(0u, self.ir.num_live_nodes) |ln_idx| {
|
|
debug!("%s", self.ln_str(LiveNode(ln_idx)));
|
|
}
|
|
body.node.id
|
|
},
|
|
entry_ln.to_str());
|
|
|
|
entry_ln
|
|
}
|
|
|
|
fn propagate_through_fn_block(decl: fn_decl, blk: blk) -> LiveNode {
|
|
// inputs passed by & mode should be considered live on exit:
|
|
for decl.inputs.each |arg| {
|
|
match ty::resolved_mode(self.tcx, arg.mode) {
|
|
by_val | by_ref => {
|
|
// By val and by ref do not own, so register a
|
|
// read at the end. This will prevent us from
|
|
// moving out of such variables but also prevent
|
|
// us from registering last uses and so forth.
|
|
do pat_util::pat_bindings(self.tcx.def_map, arg.pat)
|
|
|_bm, arg_id, _sp, _path|
|
|
{
|
|
let var = self.variable(arg_id, blk.span);
|
|
self.acc(self.s.exit_ln, var, ACC_READ);
|
|
}
|
|
}
|
|
by_copy => {
|
|
// By copy is an owned mode. If we don't use the
|
|
// variable, nobody will.
|
|
}
|
|
}
|
|
}
|
|
|
|
// the fallthrough exit is only for those cases where we do not
|
|
// explicitly return:
|
|
self.init_from_succ(self.s.fallthrough_ln, self.s.exit_ln);
|
|
if blk.node.expr.is_none() {
|
|
self.acc(self.s.fallthrough_ln, self.s.no_ret_var, ACC_READ)
|
|
}
|
|
|
|
self.propagate_through_block(blk, self.s.fallthrough_ln)
|
|
}
|
|
|
|
fn propagate_through_block(blk: blk, succ: LiveNode) -> LiveNode {
|
|
let succ = self.propagate_through_opt_expr(blk.node.expr, succ);
|
|
do blk.node.stmts.foldr(succ) |stmt, succ| {
|
|
self.propagate_through_stmt(*stmt, succ)
|
|
}
|
|
}
|
|
|
|
fn propagate_through_stmt(stmt: @stmt, succ: LiveNode) -> LiveNode {
|
|
match stmt.node {
|
|
stmt_decl(decl, _) => {
|
|
return self.propagate_through_decl(decl, succ);
|
|
}
|
|
|
|
stmt_expr(expr, _) | stmt_semi(expr, _) => {
|
|
return self.propagate_through_expr(expr, succ);
|
|
}
|
|
|
|
stmt_mac(*) => {
|
|
self.tcx.sess.span_bug(stmt.span, ~"unexpanded macro");
|
|
}
|
|
}
|
|
}
|
|
|
|
fn propagate_through_decl(decl: @decl, succ: LiveNode) -> LiveNode {
|
|
match /*bad*/copy decl.node {
|
|
decl_local(locals) => {
|
|
do locals.foldr(succ) |local, succ| {
|
|
self.propagate_through_local(*local, succ)
|
|
}
|
|
}
|
|
decl_item(_) => {
|
|
succ
|
|
}
|
|
}
|
|
}
|
|
|
|
fn propagate_through_local(local: @local, succ: LiveNode) -> LiveNode {
|
|
// Note: we mark the variable as defined regardless of whether
|
|
// there is an initializer. Initially I had thought to only mark
|
|
// the live variable as defined if it was initialized, and then we
|
|
// could check for uninit variables just by scanning what is live
|
|
// at the start of the function. But that doesn't work so well for
|
|
// immutable variables defined in a loop:
|
|
// loop { let x; x = 5; }
|
|
// because the "assignment" loops back around and generates an error.
|
|
//
|
|
// So now we just check that variables defined w/o an
|
|
// initializer are not live at the point of their
|
|
// initialization, which is mildly more complex than checking
|
|
// once at the func header but otherwise equivalent.
|
|
|
|
let succ = self.propagate_through_opt_expr(local.node.init, succ);
|
|
self.define_bindings_in_pat(local.node.pat, succ)
|
|
}
|
|
|
|
fn propagate_through_exprs(exprs: ~[@expr],
|
|
succ: LiveNode) -> LiveNode {
|
|
do exprs.foldr(succ) |expr, succ| {
|
|
self.propagate_through_expr(*expr, succ)
|
|
}
|
|
}
|
|
|
|
fn propagate_through_opt_expr(opt_expr: Option<@expr>,
|
|
succ: LiveNode) -> LiveNode {
|
|
do opt_expr.foldl(succ) |succ, expr| {
|
|
self.propagate_through_expr(*expr, *succ)
|
|
}
|
|
}
|
|
|
|
fn propagate_through_expr(expr: @expr, succ: LiveNode) -> LiveNode {
|
|
debug!("propagate_through_expr: %s",
|
|
expr_to_str(expr, self.tcx.sess.intr()));
|
|
|
|
match /*bad*/copy expr.node {
|
|
// Interesting cases with control flow or which gen/kill
|
|
|
|
expr_path(_) => {
|
|
self.access_path(expr, succ, ACC_READ | ACC_USE)
|
|
}
|
|
|
|
expr_field(e, _, _) => {
|
|
self.propagate_through_expr(e, succ)
|
|
}
|
|
|
|
expr_fn(_, _, ref blk, _) | expr_fn_block(_, ref blk) => {
|
|
debug!("%s is an expr_fn or expr_fn_block",
|
|
expr_to_str(expr, self.tcx.sess.intr()));
|
|
|
|
/*
|
|
The next-node for a break is the successor of the entire
|
|
loop. The next-node for a continue is the top of this loop.
|
|
*/
|
|
self.with_loop_nodes((*blk).node.id, succ,
|
|
self.live_node(expr.id, expr.span), || {
|
|
|
|
// the construction of a closure itself is not important,
|
|
// but we have to consider the closed over variables.
|
|
let caps = self.ir.captures(expr);
|
|
do caps.foldr(succ) |cap, succ| {
|
|
self.init_from_succ(cap.ln, succ);
|
|
let var = self.variable(cap.var_nid, expr.span);
|
|
self.acc(cap.ln, var, ACC_READ | ACC_USE);
|
|
cap.ln
|
|
}
|
|
})
|
|
}
|
|
|
|
expr_if(cond, ref then, els) => {
|
|
//
|
|
// (cond)
|
|
// |
|
|
// v
|
|
// (expr)
|
|
// / \
|
|
// | |
|
|
// v v
|
|
// (then)(els)
|
|
// | |
|
|
// v v
|
|
// ( succ )
|
|
//
|
|
let else_ln = self.propagate_through_opt_expr(els, succ);
|
|
let then_ln = self.propagate_through_block((*then), succ);
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
self.init_from_succ(ln, else_ln);
|
|
self.merge_from_succ(ln, then_ln, false);
|
|
self.propagate_through_expr(cond, ln)
|
|
}
|
|
|
|
expr_while(cond, ref blk) => {
|
|
self.propagate_through_loop(expr, Some(cond), (*blk), succ)
|
|
}
|
|
|
|
// Note that labels have been resolved, so we don't need to look
|
|
// at the label ident
|
|
expr_loop(ref blk, _) => {
|
|
self.propagate_through_loop(expr, None, (*blk), succ)
|
|
}
|
|
|
|
expr_match(e, ref arms) => {
|
|
//
|
|
// (e)
|
|
// |
|
|
// v
|
|
// (expr)
|
|
// / | \
|
|
// | | |
|
|
// v v v
|
|
// (..arms..)
|
|
// | | |
|
|
// v v v
|
|
// ( succ )
|
|
//
|
|
//
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
self.init_empty(ln, succ);
|
|
let mut first_merge = true;
|
|
for (*arms).each |arm| {
|
|
let body_succ =
|
|
self.propagate_through_block(arm.body, succ);
|
|
let guard_succ =
|
|
self.propagate_through_opt_expr(arm.guard, body_succ);
|
|
let arm_succ =
|
|
self.define_bindings_in_arm_pats(arm.pats, guard_succ);
|
|
self.merge_from_succ(ln, arm_succ, first_merge);
|
|
first_merge = false;
|
|
};
|
|
self.propagate_through_expr(e, ln)
|
|
}
|
|
|
|
expr_ret(o_e) => {
|
|
// ignore succ and subst exit_ln:
|
|
self.propagate_through_opt_expr(o_e, self.s.exit_ln)
|
|
}
|
|
|
|
expr_break(opt_label) => {
|
|
// Find which label this break jumps to
|
|
let sc = self.find_loop_scope(opt_label, expr.id, expr.span);
|
|
|
|
// Now that we know the label we're going to,
|
|
// look it up in the break loop nodes table
|
|
|
|
match self.break_ln.find(&sc) {
|
|
Some(b) => b,
|
|
None => self.tcx.sess.span_bug(expr.span,
|
|
~"Break to unknown label")
|
|
}
|
|
}
|
|
|
|
expr_again(opt_label) => {
|
|
// Find which label this expr continues to to
|
|
let sc = self.find_loop_scope(opt_label, expr.id, expr.span);
|
|
|
|
// Now that we know the label we're going to,
|
|
// look it up in the continue loop nodes table
|
|
|
|
match self.cont_ln.find(&sc) {
|
|
Some(b) => b,
|
|
None => self.tcx.sess.span_bug(expr.span,
|
|
~"Loop to unknown label")
|
|
}
|
|
}
|
|
|
|
expr_assign(l, r) => {
|
|
// see comment on lvalues in
|
|
// propagate_through_lvalue_components()
|
|
let succ = self.write_lvalue(l, succ, ACC_WRITE);
|
|
let succ = self.propagate_through_lvalue_components(l, succ);
|
|
self.propagate_through_expr(r, succ)
|
|
}
|
|
|
|
expr_swap(l, r) => {
|
|
// see comment on lvalues in
|
|
// propagate_through_lvalue_components()
|
|
|
|
// I count swaps as `used` cause it might be something like:
|
|
// foo.bar <-> x
|
|
// and I am too lazy to distinguish this case from
|
|
// y <-> x
|
|
// (where both x, y are unused) just for a warning.
|
|
let succ = self.write_lvalue(r, succ, ACC_WRITE|ACC_READ|ACC_USE);
|
|
let succ = self.write_lvalue(l, succ, ACC_WRITE|ACC_READ|ACC_USE);
|
|
let succ = self.propagate_through_lvalue_components(r, succ);
|
|
self.propagate_through_lvalue_components(l, succ)
|
|
}
|
|
|
|
expr_assign_op(_, l, r) => {
|
|
// see comment on lvalues in
|
|
// propagate_through_lvalue_components()
|
|
let succ = self.write_lvalue(l, succ, ACC_WRITE|ACC_READ);
|
|
let succ = self.propagate_through_expr(r, succ);
|
|
self.propagate_through_lvalue_components(l, succ)
|
|
}
|
|
|
|
// Uninteresting cases: just propagate in rev exec order
|
|
|
|
expr_vstore(expr, _) => {
|
|
self.propagate_through_expr(expr, succ)
|
|
}
|
|
|
|
expr_vec(exprs, _) => {
|
|
self.propagate_through_exprs(exprs, succ)
|
|
}
|
|
|
|
expr_repeat(element, count, _) => {
|
|
let succ = self.propagate_through_expr(count, succ);
|
|
self.propagate_through_expr(element, succ)
|
|
}
|
|
|
|
expr_rec(ref fields, with_expr) => {
|
|
let succ = self.propagate_through_opt_expr(with_expr, succ);
|
|
do (*fields).foldr(succ) |field, succ| {
|
|
self.propagate_through_expr(field.node.expr, succ)
|
|
}
|
|
}
|
|
|
|
expr_struct(_, ref fields, with_expr) => {
|
|
let succ = self.propagate_through_opt_expr(with_expr, succ);
|
|
do (*fields).foldr(succ) |field, succ| {
|
|
self.propagate_through_expr(field.node.expr, succ)
|
|
}
|
|
}
|
|
|
|
expr_call(f, args, _) => {
|
|
// calling a fn with bot return type means that the fn
|
|
// will fail, and hence the successors can be ignored
|
|
let t_ret = ty::ty_fn_ret(ty::expr_ty(self.tcx, f));
|
|
let succ = if ty::type_is_bot(t_ret) {self.s.exit_ln}
|
|
else {succ};
|
|
let succ = self.propagate_through_exprs(args, succ);
|
|
self.propagate_through_expr(f, succ)
|
|
}
|
|
|
|
expr_method_call(rcvr, _, _, args, _) => {
|
|
// calling a method with bot return type means that the method
|
|
// will fail, and hence the successors can be ignored
|
|
let t_ret = ty::ty_fn_ret(ty::node_id_to_type(self.tcx,
|
|
expr.callee_id));
|
|
let succ = if ty::type_is_bot(t_ret) {self.s.exit_ln}
|
|
else {succ};
|
|
let succ = self.propagate_through_exprs(args, succ);
|
|
self.propagate_through_expr(rcvr, succ)
|
|
}
|
|
|
|
expr_tup(exprs) => {
|
|
self.propagate_through_exprs(exprs, succ)
|
|
}
|
|
|
|
expr_binary(op, l, r) if ast_util::lazy_binop(op) => {
|
|
let r_succ = self.propagate_through_expr(r, succ);
|
|
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
self.init_from_succ(ln, succ);
|
|
self.merge_from_succ(ln, r_succ, false);
|
|
|
|
self.propagate_through_expr(l, ln)
|
|
}
|
|
|
|
expr_log(_, l, r) |
|
|
expr_index(l, r) |
|
|
expr_binary(_, l, r) => {
|
|
self.propagate_through_exprs(~[l, r], succ)
|
|
}
|
|
|
|
expr_assert(e) |
|
|
expr_addr_of(_, e) |
|
|
expr_copy(e) |
|
|
expr_loop_body(e) |
|
|
expr_do_body(e) |
|
|
expr_cast(e, _) |
|
|
expr_unary(_, e) |
|
|
expr_paren(e) => {
|
|
self.propagate_through_expr(e, succ)
|
|
}
|
|
|
|
expr_lit(*) => {
|
|
succ
|
|
}
|
|
|
|
expr_block(ref blk) => {
|
|
self.propagate_through_block((*blk), succ)
|
|
}
|
|
|
|
expr_mac(*) => {
|
|
self.tcx.sess.span_bug(expr.span, ~"unexpanded macro");
|
|
}
|
|
}
|
|
}
|
|
|
|
fn propagate_through_lvalue_components(expr: @expr,
|
|
succ: LiveNode) -> LiveNode {
|
|
// # Lvalues
|
|
//
|
|
// In general, the full flow graph structure for an
|
|
// assignment/move/etc can be handled in one of two ways,
|
|
// depending on whether what is being assigned is a "tracked
|
|
// value" or not. A tracked value is basically a local
|
|
// variable or argument.
|
|
//
|
|
// The two kinds of graphs are:
|
|
//
|
|
// Tracked lvalue Untracked lvalue
|
|
// ----------------------++-----------------------
|
|
// ||
|
|
// | || |
|
|
// v || v
|
|
// (rvalue) || (rvalue)
|
|
// | || |
|
|
// v || v
|
|
// (write of lvalue) || (lvalue components)
|
|
// | || |
|
|
// v || v
|
|
// (succ) || (succ)
|
|
// ||
|
|
// ----------------------++-----------------------
|
|
//
|
|
// I will cover the two cases in turn:
|
|
//
|
|
// # Tracked lvalues
|
|
//
|
|
// A tracked lvalue is a local variable/argument `x`. In
|
|
// these cases, the link_node where the write occurs is linked
|
|
// to node id of `x`. The `write_lvalue()` routine generates
|
|
// the contents of this node. There are no subcomponents to
|
|
// consider.
|
|
//
|
|
// # Non-tracked lvalues
|
|
//
|
|
// These are lvalues like `x[5]` or `x.f`. In that case, we
|
|
// basically ignore the value which is written to but generate
|
|
// reads for the components---`x` in these two examples. The
|
|
// components reads are generated by
|
|
// `propagate_through_lvalue_components()` (this fn).
|
|
//
|
|
// # Illegal lvalues
|
|
//
|
|
// It is still possible to observe assignments to non-lvalues;
|
|
// these errors are detected in the later pass borrowck. We
|
|
// just ignore such cases and treat them as reads.
|
|
|
|
match expr.node {
|
|
expr_path(_) => succ,
|
|
expr_field(e, _, _) => self.propagate_through_expr(e, succ),
|
|
_ => self.propagate_through_expr(expr, succ)
|
|
}
|
|
}
|
|
|
|
// see comment on propagate_through_lvalue()
|
|
fn write_lvalue(expr: @expr,
|
|
succ: LiveNode,
|
|
acc: uint) -> LiveNode {
|
|
match expr.node {
|
|
expr_path(_) => self.access_path(expr, succ, acc),
|
|
|
|
// We do not track other lvalues, so just propagate through
|
|
// to their subcomponents. Also, it may happen that
|
|
// non-lvalues occur here, because those are detected in the
|
|
// later pass borrowck.
|
|
_ => succ
|
|
}
|
|
}
|
|
|
|
fn access_path(expr: @expr, succ: LiveNode, acc: uint) -> LiveNode {
|
|
let def = self.tcx.def_map.get(&expr.id);
|
|
match relevant_def(def) {
|
|
Some(nid) => {
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
if acc != 0u {
|
|
self.init_from_succ(ln, succ);
|
|
let var = self.variable(nid, expr.span);
|
|
self.acc(ln, var, acc);
|
|
}
|
|
ln
|
|
}
|
|
None => succ
|
|
}
|
|
}
|
|
|
|
fn propagate_through_loop(expr: @expr,
|
|
cond: Option<@expr>,
|
|
body: blk,
|
|
succ: LiveNode) -> LiveNode {
|
|
|
|
/*
|
|
|
|
We model control flow like this:
|
|
|
|
(cond) <--+
|
|
| |
|
|
v |
|
|
+-- (expr) |
|
|
| | |
|
|
| v |
|
|
| (body) ---+
|
|
|
|
|
|
|
|
v
|
|
(succ)
|
|
|
|
*/
|
|
|
|
|
|
// first iteration:
|
|
let mut first_merge = true;
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
self.init_empty(ln, succ);
|
|
if cond.is_some() {
|
|
// if there is a condition, then it's possible we bypass
|
|
// the body altogether. otherwise, the only way is via a
|
|
// break in the loop body.
|
|
self.merge_from_succ(ln, succ, first_merge);
|
|
first_merge = false;
|
|
}
|
|
debug!("propagate_through_loop: using id for loop body %d %s",
|
|
expr.id, block_to_str(body, self.tcx.sess.intr()));
|
|
|
|
let cond_ln = self.propagate_through_opt_expr(cond, ln);
|
|
let body_ln = self.with_loop_nodes(expr.id, succ, ln, || {
|
|
self.propagate_through_block(body, cond_ln)
|
|
});
|
|
|
|
// repeat until fixed point is reached:
|
|
while self.merge_from_succ(ln, body_ln, first_merge) {
|
|
first_merge = false;
|
|
assert cond_ln == self.propagate_through_opt_expr(cond, ln);
|
|
assert body_ln == self.with_loop_nodes(expr.id, succ, ln,
|
|
|| {
|
|
self.propagate_through_block(body, cond_ln)
|
|
});
|
|
}
|
|
|
|
cond_ln
|
|
}
|
|
|
|
fn with_loop_nodes<R>(loop_node_id: node_id,
|
|
break_ln: LiveNode,
|
|
cont_ln: LiveNode,
|
|
f: fn() -> R) -> R {
|
|
debug!("with_loop_nodes: %d %u", loop_node_id, *break_ln);
|
|
self.loop_scope.push(loop_node_id);
|
|
self.break_ln.insert(loop_node_id, break_ln);
|
|
self.cont_ln.insert(loop_node_id, cont_ln);
|
|
let r = f();
|
|
self.loop_scope.pop();
|
|
move r
|
|
}
|
|
}
|
|
|
|
// _______________________________________________________________________
|
|
// Checking for error conditions
|
|
|
|
fn check_local(local: @local, &&self: @Liveness, vt: vt<@Liveness>) {
|
|
match local.node.init {
|
|
Some(_) => {
|
|
|
|
// Initializer:
|
|
self.warn_about_unused_or_dead_vars_in_pat(local.node.pat);
|
|
if !local.node.is_mutbl {
|
|
self.check_for_reassignments_in_pat(local.node.pat);
|
|
}
|
|
}
|
|
None => {
|
|
|
|
// No initializer: the variable might be unused; if not, it
|
|
// should not be live at this point.
|
|
|
|
debug!("check_local() with no initializer");
|
|
do self.pat_bindings(local.node.pat) |ln, var, sp| {
|
|
if !self.warn_about_unused(sp, ln, var) {
|
|
match self.live_on_exit(ln, var) {
|
|
None => { /* not live: good */ }
|
|
Some(lnk) => {
|
|
self.report_illegal_read(
|
|
local.span, lnk, var,
|
|
PossiblyUninitializedVariable);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
visit::visit_local(local, self, vt);
|
|
}
|
|
|
|
fn check_arm(arm: arm, &&self: @Liveness, vt: vt<@Liveness>) {
|
|
do self.arm_pats_bindings(arm.pats) |ln, var, sp| {
|
|
self.warn_about_unused(sp, ln, var);
|
|
}
|
|
visit::visit_arm(arm, self, vt);
|
|
}
|
|
|
|
fn check_expr(expr: @expr, &&self: @Liveness, vt: vt<@Liveness>) {
|
|
match /*bad*/copy expr.node {
|
|
expr_path(_) => {
|
|
for self.variable_from_def_map(expr.id, expr.span).each |var| {
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
self.consider_last_use(expr, ln, *var);
|
|
|
|
match self.ir.variable_moves_map.find(&expr.id) {
|
|
None => {}
|
|
Some(entire_expr) => {
|
|
debug!("(checking expr) is a move: `%s`",
|
|
expr_to_str(expr, self.tcx.sess.intr()));
|
|
self.check_move_from_var(ln, *var, entire_expr);
|
|
}
|
|
}
|
|
}
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
expr_fn(*) | expr_fn_block(*) => {
|
|
let caps = self.ir.captures(expr);
|
|
for caps.each |cap| {
|
|
let var = self.variable(cap.var_nid, expr.span);
|
|
self.consider_last_use(expr, cap.ln, var);
|
|
if cap.is_move {
|
|
self.check_move_from_var(cap.ln, var, expr);
|
|
}
|
|
}
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
expr_assign(l, r) => {
|
|
self.check_lvalue(l, vt);
|
|
(vt.visit_expr)(r, self, vt);
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
expr_assign_op(_, l, _) => {
|
|
self.check_lvalue(l, vt);
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
|
|
// no correctness conditions related to liveness
|
|
expr_call(*) | expr_method_call(*) |
|
|
expr_if(*) | expr_match(*) |
|
|
expr_while(*) | expr_loop(*) |
|
|
expr_index(*) | expr_field(*) | expr_vstore(*) |
|
|
expr_vec(*) | expr_rec(*) | expr_tup(*) |
|
|
expr_log(*) | expr_binary(*) |
|
|
expr_assert(*) | expr_copy(*) |
|
|
expr_loop_body(*) | expr_do_body(*) |
|
|
expr_cast(*) | expr_unary(*) |
|
|
expr_ret(*) | expr_break(*) | expr_again(*) | expr_lit(_) |
|
|
expr_block(*) | expr_swap(*) | expr_mac(*) | expr_addr_of(*) |
|
|
expr_struct(*) | expr_repeat(*) | expr_paren(*) => {
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_fn(_fk: visit::fn_kind, _decl: fn_decl,
|
|
_body: blk, _sp: span, _id: node_id,
|
|
&&_self: @Liveness, _v: vt<@Liveness>) {
|
|
// do not check contents of nested fns
|
|
}
|
|
|
|
enum ReadKind {
|
|
PossiblyUninitializedVariable,
|
|
PossiblyUninitializedField,
|
|
MovedValue,
|
|
PartiallyMovedValue
|
|
}
|
|
|
|
impl @Liveness {
|
|
fn check_ret(id: node_id, sp: span, _fk: visit::fn_kind,
|
|
entry_ln: LiveNode) {
|
|
if self.live_on_entry(entry_ln, self.s.no_ret_var).is_some() {
|
|
// if no_ret_var is live, then we fall off the end of the
|
|
// function without any kind of return expression:
|
|
|
|
let t_ret = ty::ty_fn_ret(ty::node_id_to_type(self.tcx, id));
|
|
if ty::type_is_nil(t_ret) {
|
|
// for nil return types, it is ok to not return a value expl.
|
|
} else if ty::type_is_bot(t_ret) {
|
|
// for bot return types, not ok. Function should fail.
|
|
self.tcx.sess.span_err(
|
|
sp, ~"some control paths may return");
|
|
} else {
|
|
self.tcx.sess.span_err(
|
|
sp, ~"not all control paths return a value");
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_move_from_var(ln: LiveNode,
|
|
var: Variable,
|
|
move_expr: @expr)
|
|
{
|
|
/*!
|
|
*
|
|
* Checks whether `var` is live on entry to any of the
|
|
* successors of `ln`. If it is, report an error.
|
|
* `move_expr` is the expression which caused the variable
|
|
* to be moved.
|
|
*
|
|
* Note that `move_expr` is not necessarily a reference to the
|
|
* variable. It might be an expression like `x.f` which could
|
|
* cause a move of the variable `x`, or a closure creation.
|
|
*/
|
|
|
|
debug!("check_move_from_var(%s, %s)",
|
|
ln.to_str(), var.to_str());
|
|
|
|
match self.live_on_exit(ln, var) {
|
|
None => {}
|
|
Some(lnk) => self.report_illegal_move(lnk, var, move_expr)
|
|
}
|
|
}
|
|
|
|
fn consider_last_use(expr: @expr, ln: LiveNode, var: Variable) {
|
|
debug!("consider_last_use(expr.id=%?, ln=%s, var=%s)",
|
|
expr.id, ln.to_str(), var.to_str());
|
|
|
|
match self.live_on_exit(ln, var) {
|
|
Some(_) => {}
|
|
None => self.ir.add_last_use(expr.id, var)
|
|
}
|
|
}
|
|
|
|
fn check_lvalue(expr: @expr, vt: vt<@Liveness>) {
|
|
match expr.node {
|
|
expr_path(_) => {
|
|
match self.tcx.def_map.get(&expr.id) {
|
|
def_local(nid, false) => {
|
|
// Assignment to an immutable variable or argument:
|
|
// only legal if there is no later assignment.
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
let var = self.variable(nid, expr.span);
|
|
self.check_for_reassignment(ln, var, expr.span);
|
|
self.warn_about_dead_assign(expr.span, ln, var);
|
|
}
|
|
def => {
|
|
match relevant_def(def) {
|
|
Some(nid) => {
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
let var = self.variable(nid, expr.span);
|
|
self.warn_about_dead_assign(expr.span, ln, var);
|
|
}
|
|
None => {}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
_ => {
|
|
// For other kinds of lvalues, no checks are required,
|
|
// and any embedded expressions are actually rvalues
|
|
visit::visit_expr(expr, self, vt);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_for_reassignments_in_pat(pat: @pat) {
|
|
do self.pat_bindings(pat) |ln, var, sp| {
|
|
self.check_for_reassignment(ln, var, sp);
|
|
}
|
|
}
|
|
|
|
fn check_for_reassignment(ln: LiveNode, var: Variable,
|
|
orig_span: span) {
|
|
match self.assigned_on_exit(ln, var) {
|
|
Some(ExprNode(span)) => {
|
|
self.tcx.sess.span_err(
|
|
span,
|
|
~"re-assignment of immutable variable");
|
|
|
|
self.tcx.sess.span_note(
|
|
orig_span,
|
|
~"prior assignment occurs here");
|
|
}
|
|
Some(lnk) => {
|
|
self.tcx.sess.span_bug(
|
|
orig_span,
|
|
fmt!("illegal writer: %?", lnk));
|
|
}
|
|
None => {}
|
|
}
|
|
}
|
|
|
|
fn report_illegal_move(lnk: LiveNodeKind,
|
|
var: Variable,
|
|
move_expr: @expr)
|
|
{
|
|
// the only time that it is possible to have a moved variable
|
|
// used by ExitNode would be arguments or fields in a ctor.
|
|
// we give a slightly different error message in those cases.
|
|
if lnk == ExitNode {
|
|
// FIXME #4715: this seems like it should be reported in the
|
|
// borrow checker
|
|
let vk = self.ir.var_kinds[*var];
|
|
match vk {
|
|
Arg(_, name, _) => {
|
|
self.tcx.sess.span_err(
|
|
move_expr.span,
|
|
fmt!("illegal move from argument `%s`, which is not \
|
|
copy or move mode", self.tcx.sess.str_of(name)));
|
|
return;
|
|
}
|
|
Local(*) | ImplicitRet => {
|
|
self.tcx.sess.span_bug(
|
|
move_expr.span,
|
|
fmt!("illegal reader (%?) for `%?`",
|
|
lnk, vk));
|
|
}
|
|
}
|
|
}
|
|
|
|
match move_expr.node {
|
|
expr_fn(*) | expr_fn_block(*) => {
|
|
self.report_illegal_read(
|
|
move_expr.span, lnk, var, MovedValue);
|
|
let name = self.ir.variable_name(var);
|
|
self.tcx.sess.span_note(
|
|
move_expr.span,
|
|
fmt!("`%s` moved into closure environment here \
|
|
because its type is moved by default",
|
|
name));
|
|
}
|
|
expr_path(*) => {
|
|
self.report_illegal_read(
|
|
move_expr.span, lnk, var, MovedValue);
|
|
self.report_move_location(
|
|
move_expr, var, "", "it");
|
|
}
|
|
expr_field(*) => {
|
|
self.report_illegal_read(
|
|
move_expr.span, lnk, var, PartiallyMovedValue);
|
|
self.report_move_location(
|
|
move_expr, var, "field of ", "the field");
|
|
}
|
|
expr_index(*) => {
|
|
self.report_illegal_read(
|
|
move_expr.span, lnk, var, PartiallyMovedValue);
|
|
self.report_move_location(
|
|
move_expr, var, "element of ", "the element");
|
|
}
|
|
_ => {
|
|
self.report_illegal_read(
|
|
move_expr.span, lnk, var, PartiallyMovedValue);
|
|
self.report_move_location(
|
|
move_expr, var, "subcomponent of ", "the subcomponent");
|
|
}
|
|
};
|
|
}
|
|
|
|
fn report_move_location(move_expr: @expr,
|
|
var: Variable,
|
|
expr_descr: &str,
|
|
pronoun: &str)
|
|
{
|
|
let move_expr_ty = ty::expr_ty(self.tcx, move_expr);
|
|
let name = self.ir.variable_name(var);
|
|
self.tcx.sess.span_note(
|
|
move_expr.span,
|
|
fmt!("%s`%s` moved here because %s has type %s, \
|
|
which is moved by default (use `copy` to override)",
|
|
expr_descr, name, pronoun,
|
|
ty_to_str(self.tcx, move_expr_ty)));
|
|
}
|
|
|
|
fn report_illegal_read(chk_span: span,
|
|
lnk: LiveNodeKind,
|
|
var: Variable,
|
|
rk: ReadKind) {
|
|
let msg = match rk {
|
|
PossiblyUninitializedVariable => "possibly uninitialized \
|
|
variable",
|
|
PossiblyUninitializedField => "possibly uninitialized field",
|
|
MovedValue => "moved value",
|
|
PartiallyMovedValue => "partially moved value"
|
|
};
|
|
let name = self.ir.variable_name(var);
|
|
match lnk {
|
|
FreeVarNode(span) => {
|
|
self.tcx.sess.span_err(
|
|
span,
|
|
fmt!("capture of %s: `%s`", msg, name));
|
|
}
|
|
ExprNode(span) => {
|
|
self.tcx.sess.span_err(
|
|
span,
|
|
fmt!("use of %s: `%s`", msg, name));
|
|
}
|
|
ExitNode | VarDefNode(_) => {
|
|
self.tcx.sess.span_bug(
|
|
chk_span,
|
|
fmt!("illegal reader: %?", lnk));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn should_warn(var: Variable) -> Option<~str> {
|
|
let name = self.ir.variable_name(var);
|
|
if name[0] == ('_' as u8) {None} else {Some(name)}
|
|
}
|
|
|
|
fn warn_about_unused_args(decl: fn_decl, entry_ln: LiveNode) {
|
|
for decl.inputs.each |arg| {
|
|
do pat_util::pat_bindings(self.tcx.def_map, arg.pat)
|
|
|_bm, p_id, sp, _n| {
|
|
let var = self.variable(p_id, sp);
|
|
self.warn_about_unused(sp, entry_ln, var);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn warn_about_unused_or_dead_vars_in_pat(pat: @pat) {
|
|
do self.pat_bindings(pat) |ln, var, sp| {
|
|
if !self.warn_about_unused(sp, ln, var) {
|
|
self.warn_about_dead_assign(sp, ln, var);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn warn_about_unused(sp: span, ln: LiveNode, var: Variable) -> bool {
|
|
if !self.used_on_entry(ln, var) {
|
|
for self.should_warn(var).each |name| {
|
|
|
|
// annoying: for parameters in funcs like `fn(x: int)
|
|
// {ret}`, there is only one node, so asking about
|
|
// assigned_on_exit() is not meaningful.
|
|
let is_assigned = if ln == self.s.exit_ln {
|
|
false
|
|
} else {
|
|
self.assigned_on_exit(ln, var).is_some()
|
|
};
|
|
|
|
if is_assigned {
|
|
// FIXME(#3266)--make liveness warnings lintable
|
|
self.tcx.sess.span_warn(
|
|
sp, fmt!("variable `%s` is assigned to, \
|
|
but never used", *name));
|
|
} else {
|
|
// FIXME(#3266)--make liveness warnings lintable
|
|
self.tcx.sess.span_warn(
|
|
sp, fmt!("unused variable: `%s`", *name));
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
fn warn_about_dead_assign(sp: span, ln: LiveNode, var: Variable) {
|
|
if self.live_on_exit(ln, var).is_none() {
|
|
for self.should_warn(var).each |name| {
|
|
// FIXME(#3266)--make liveness warnings lintable
|
|
self.tcx.sess.span_warn(
|
|
sp,
|
|
fmt!("value assigned to `%s` is never read", *name));
|
|
}
|
|
}
|
|
}
|
|
}
|