1655 lines
56 KiB
Rust
1655 lines
56 KiB
Rust
// Copyright 2012-2013 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 middle::lint::{unused_variable, dead_assignment};
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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 std::cast::transmute;
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use std::hashmap::HashMap;
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use std::io;
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use std::str;
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use std::to_str;
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use std::uint;
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use std::vec;
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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, ast_util};
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use syntax::visit::{Visitor,fn_kind};
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#[deriving(Eq)]
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struct Variable(uint);
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#[deriving(Eq)]
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struct LiveNode(uint);
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impl Clone for LiveNode {
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fn clone(&self) -> LiveNode {
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LiveNode(**self)
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}
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}
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#[deriving(Eq)]
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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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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) => format!("Free var node [{}]", cm.span_to_str(s)),
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ExprNode(s) => format!("Expr node [{}]", cm.span_to_str(s)),
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VarDefNode(s) => format!("Var def node [{}]", cm.span_to_str(s)),
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ExitNode => ~"Exit node"
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}
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}
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struct LivenessVisitor;
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impl Visitor<@mut IrMaps> for LivenessVisitor {
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fn visit_fn(&mut self, fk:&fn_kind, fd:&fn_decl, b:P<Block>, s:Span, n:NodeId, e:@mut IrMaps) {
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visit_fn(self, fk, fd, b, s, n, e);
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}
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fn visit_local(&mut self, l:@Local, e:@mut IrMaps) { visit_local(self, l, e); }
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fn visit_expr(&mut self, ex:@Expr, e:@mut IrMaps) { visit_expr(self, ex, e); }
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fn visit_arm(&mut self, a:&Arm, e:@mut IrMaps) { visit_arm(self, a, e); }
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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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capture_map: moves::CaptureMap,
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crate: &Crate) {
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let mut visitor = LivenessVisitor;
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let initial_maps = @mut IrMaps(tcx,
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method_map,
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capture_map);
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visit::walk_crate(&mut visitor, crate, initial_maps);
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tcx.sess.abort_if_errors();
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}
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impl to_str::ToStr for LiveNode {
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fn to_str(&self) -> ~str { format!("ln({})", **self) }
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}
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impl to_str::ToStr for Variable {
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fn to_str(&self) -> ~str { format!("v({})", **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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pub fn is_valid(&self) -> bool {
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**self != uint::max_value
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}
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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: NodeId
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}
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enum LocalKind {
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FromMatch(BindingMode),
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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: NodeId,
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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(NodeId, Ident),
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Local(LocalInfo),
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ImplicitRet
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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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capture_map: moves::CaptureMap,
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num_live_nodes: uint,
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num_vars: uint,
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live_node_map: HashMap<NodeId, LiveNode>,
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variable_map: HashMap<NodeId, Variable>,
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capture_info_map: HashMap<NodeId, @~[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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capture_map: moves::CaptureMap)
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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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capture_map: capture_map,
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num_live_nodes: 0,
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num_vars: 0,
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live_node_map: HashMap::new(),
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variable_map: HashMap::new(),
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capture_info_map: HashMap::new(),
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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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pub 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!("{} is of kind {}", 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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pub fn add_live_node_for_node(&mut self,
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node_id: NodeId,
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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!("{} is node {}", ln.to_str(), node_id);
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}
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pub 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, .. }) | 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!("{} is {:?}", v.to_str(), vk);
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v
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}
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pub fn variable(&mut self, node_id: NodeId, 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, format!("No variable registered for id {}", node_id));
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}
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}
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}
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pub fn variable_name(&mut self, var: Variable) -> @str {
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match self.var_kinds[*var] {
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Local(LocalInfo { ident: nm, .. }) | Arg(_, nm) => {
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self.tcx.sess.str_of(nm)
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},
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ImplicitRet => @"<implicit-ret>"
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}
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}
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pub fn set_captures(&mut self, node_id: NodeId, cs: ~[CaptureInfo]) {
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self.capture_info_map.insert(node_id, @cs);
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}
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pub 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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pub fn lnk(&mut self, ln: LiveNode) -> LiveNodeKind {
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self.lnks[*ln]
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}
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}
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impl Visitor<()> for Liveness {
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fn visit_fn(&mut self, fk:&fn_kind, fd:&fn_decl, b:P<Block>, s:Span, n:NodeId, _:()) {
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check_fn(self, fk, fd, b, s, n);
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}
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fn visit_local(&mut self, l:@Local, _:()) {
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check_local(self, l);
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}
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fn visit_expr(&mut self, ex:@Expr, _:()) {
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check_expr(self, ex);
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}
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fn visit_arm(&mut self, a:&Arm, _:()) {
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check_arm(self, a);
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}
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}
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fn visit_fn(v: &mut LivenessVisitor,
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fk: &visit::fn_kind,
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decl: &fn_decl,
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body: P<Block>,
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sp: Span,
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id: NodeId,
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this: @mut IrMaps) {
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debug!("visit_fn: id={}", 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(this.tcx,
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this.method_map,
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this.capture_map);
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unsafe {
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debug!("creating fn_maps: {}", transmute::<&IrMaps, *IrMaps>(fn_maps));
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}
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for arg in decl.inputs.iter() {
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pat_util::pat_bindings(this.tcx.def_map,
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arg.pat,
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|_bm, arg_id, _x, path| {
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debug!("adding argument {}", 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));
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})
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};
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// Add `this`, whether explicit or implicit.
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match *fk {
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visit::fk_method(_, _, method) => {
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match method.explicit_self.node {
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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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}
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sty_static => {}
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}
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}
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visit::fk_item_fn(..) | visit::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::walk_fn(v, fk, decl, body, sp, id, fn_maps);
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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
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// - implicit_ret_var is a pseudo-variable that represents
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// an implicit return
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let specials = Specials {
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exit_ln: fn_maps.add_live_node(ExitNode),
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fallthrough_ln: fn_maps.add_live_node(ExitNode),
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no_ret_var: fn_maps.add_variable(ImplicitRet)
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};
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// compute liveness
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let mut lsets = Liveness(fn_maps, specials);
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let entry_ln = lsets.compute(decl, body);
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// check for various error conditions
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lsets.visit_block(body, ());
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lsets.check_ret(id, sp, fk, entry_ln);
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lsets.warn_about_unused_args(decl, entry_ln);
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}
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fn visit_local(v: &mut LivenessVisitor, local: @Local, this: @mut IrMaps) {
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let def_map = this.tcx.def_map;
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pat_util::pat_bindings(def_map, local.pat, |bm, p_id, sp, path| {
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debug!("adding local variable {}", p_id);
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let name = ast_util::path_to_ident(path);
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this.add_live_node_for_node(p_id, VarDefNode(sp));
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let kind = match local.init {
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Some(_) => FromLetWithInitializer,
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None => FromLetNoInitializer
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};
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let mutbl = match bm {
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BindByValue(MutMutable) => true,
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_ => false
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};
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this.add_variable(Local(LocalInfo {
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id: p_id,
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ident: name,
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is_mutbl: mutbl,
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kind: kind
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}));
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});
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visit::walk_local(v, local, this);
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}
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fn visit_arm(v: &mut LivenessVisitor, arm: &Arm, this: @mut IrMaps) {
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let def_map = this.tcx.def_map;
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for pat in arm.pats.iter() {
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pat_util::pat_bindings(def_map, *pat, |bm, p_id, sp, path| {
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debug!("adding local variable {} from match with bm {:?}",
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p_id, bm);
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let name = ast_util::path_to_ident(path);
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let mutbl = match bm {
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BindByValue(MutMutable) => true,
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_ => false
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};
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this.add_live_node_for_node(p_id, VarDefNode(sp));
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this.add_variable(Local(LocalInfo {
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id: p_id,
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ident: name,
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is_mutbl: mutbl,
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kind: FromMatch(bm)
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}));
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})
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}
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visit::walk_arm(v, arm, this);
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}
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fn visit_expr(v: &mut LivenessVisitor, expr: @Expr, this: @mut IrMaps) {
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match expr.node {
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// live nodes required for uses or definitions of variables:
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ExprPath(_) | ExprSelf => {
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let def = this.tcx.def_map.get_copy(&expr.id);
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debug!("expr {}: path that leads to {:?}", expr.id, def);
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if moves::moved_variable_node_id_from_def(def).is_some() {
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this.add_live_node_for_node(expr.id, ExprNode(expr.span));
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}
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visit::walk_expr(v, expr, this);
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}
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|
ExprFnBlock(..) | ExprProc(..) => {
|
|
// Interesting control flow (for loops can contain labeled
|
|
// breaks or continues)
|
|
this.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 = this.capture_map.get(&expr.id);
|
|
let mut call_caps = ~[];
|
|
for cv in cvs.iter() {
|
|
match moves::moved_variable_node_id_from_def(cv.def) {
|
|
Some(rv) => {
|
|
let cv_ln = this.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 => {}
|
|
}
|
|
}
|
|
this.set_captures(expr.id, call_caps);
|
|
|
|
visit::walk_expr(v, expr, this);
|
|
}
|
|
|
|
// live nodes required for interesting control flow:
|
|
ExprIf(..) | ExprMatch(..) | ExprWhile(..) | ExprLoop(..) => {
|
|
this.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
visit::walk_expr(v, expr, this);
|
|
}
|
|
ExprForLoop(..) => fail!("non-desugared expr_for_loop"),
|
|
ExprBinary(_, op, _, _) if ast_util::lazy_binop(op) => {
|
|
this.add_live_node_for_node(expr.id, ExprNode(expr.span));
|
|
visit::walk_expr(v, expr, this);
|
|
}
|
|
|
|
// otherwise, live nodes are not required:
|
|
ExprIndex(..) | ExprField(..) | ExprVstore(..) | ExprVec(..) |
|
|
ExprCall(..) | ExprMethodCall(..) | ExprTup(..) | ExprLogLevel |
|
|
ExprBinary(..) | ExprAddrOf(..) |
|
|
ExprDoBody(..) | ExprCast(..) | ExprUnary(..) | ExprBreak(_) |
|
|
ExprAgain(_) | ExprLit(_) | ExprRet(..) | ExprBlock(..) |
|
|
ExprAssign(..) | ExprAssignOp(..) | ExprMac(..) |
|
|
ExprStruct(..) | ExprRepeat(..) | ExprParen(..) |
|
|
ExprInlineAsm(..) => {
|
|
visit::walk_expr(v, expr, this);
|
|
}
|
|
}
|
|
}
|
|
|
|
// ______________________________________________________________________
|
|
// Computing liveness sets
|
|
//
|
|
// Actually we compute just a bit more than just liveness, but we use
|
|
// the same basic propagation framework in all cases.
|
|
|
|
#[deriving(Clone)]
|
|
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
|
|
}
|
|
|
|
static ACC_READ: uint = 1u;
|
|
static ACC_WRITE: uint = 2u;
|
|
static ACC_USE: uint = 4u;
|
|
|
|
type LiveNodeMap = @mut HashMap<NodeId, LiveNode>;
|
|
|
|
pub 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: @mut ~[NodeId],
|
|
// 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: @mut vec::from_elem(ir.num_live_nodes, invalid_node()),
|
|
users: @mut vec::from_elem(ir.num_live_nodes * ir.num_vars,
|
|
invalid_users()),
|
|
loop_scope: @mut ~[],
|
|
break_ln: @mut HashMap::new(),
|
|
cont_ln: @mut HashMap::new()
|
|
}
|
|
}
|
|
|
|
impl Liveness {
|
|
pub fn live_node(&self, node_id: NodeId, span: Span) -> LiveNode {
|
|
let ir: &mut IrMaps = self.ir;
|
|
match 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, format!("No live node registered for node {}",
|
|
node_id));
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn variable(&self, node_id: NodeId, span: Span) -> Variable {
|
|
self.ir.variable(node_id, span)
|
|
}
|
|
|
|
pub fn pat_bindings(&self,
|
|
pat: @Pat,
|
|
f: |LiveNode, Variable, Span, NodeId|) {
|
|
let def_map = self.tcx.def_map;
|
|
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, p_id);
|
|
})
|
|
}
|
|
|
|
pub fn arm_pats_bindings(&self,
|
|
pats: &[@Pat],
|
|
f: |LiveNode, Variable, Span, NodeId|) {
|
|
// 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)
|
|
}
|
|
}
|
|
|
|
pub fn define_bindings_in_pat(&self, pat: @Pat, succ: LiveNode)
|
|
-> LiveNode {
|
|
self.define_bindings_in_arm_pats([pat], succ)
|
|
}
|
|
|
|
pub fn define_bindings_in_arm_pats(&self, pats: &[@Pat], succ: LiveNode)
|
|
-> LiveNode {
|
|
let mut succ = succ;
|
|
self.arm_pats_bindings(pats, |ln, var, _sp, _id| {
|
|
self.init_from_succ(ln, succ);
|
|
self.define(ln, var);
|
|
succ = ln;
|
|
});
|
|
succ
|
|
}
|
|
|
|
pub fn idx(&self, ln: LiveNode, var: Variable) -> uint {
|
|
*ln * self.ir.num_vars + *var
|
|
}
|
|
|
|
pub fn live_on_entry(&self, 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?
|
|
*/
|
|
pub fn live_on_exit(&self, ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
self.live_on_entry(self.successors[*ln], var)
|
|
}
|
|
|
|
pub fn used_on_entry(&self, ln: LiveNode, var: Variable) -> bool {
|
|
assert!(ln.is_valid());
|
|
self.users[self.idx(ln, var)].used
|
|
}
|
|
|
|
pub fn assigned_on_entry(&self, 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}
|
|
}
|
|
|
|
pub fn assigned_on_exit(&self, ln: LiveNode, var: Variable)
|
|
-> Option<LiveNodeKind> {
|
|
self.assigned_on_entry(self.successors[*ln], var)
|
|
}
|
|
|
|
pub fn indices2(&self,
|
|
ln: LiveNode,
|
|
succ_ln: LiveNode,
|
|
op: |uint, uint|) {
|
|
let node_base_idx = self.idx(ln, Variable(0u));
|
|
let succ_base_idx = self.idx(succ_ln, Variable(0u));
|
|
for var_idx in range(0u, self.ir.num_vars) {
|
|
op(node_base_idx + var_idx, succ_base_idx + var_idx);
|
|
}
|
|
}
|
|
|
|
pub fn write_vars(&self,
|
|
wr: &mut io::Writer,
|
|
ln: LiveNode,
|
|
test: |uint| -> LiveNode) {
|
|
let node_base_idx = self.idx(ln, Variable(0));
|
|
for var_idx in range(0u, self.ir.num_vars) {
|
|
let idx = node_base_idx + var_idx;
|
|
if test(idx).is_valid() {
|
|
write!(wr, " {}", Variable(var_idx).to_str());
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn find_loop_scope(&self,
|
|
opt_label: Option<Name>,
|
|
id: NodeId,
|
|
sp: Span)
|
|
-> NodeId {
|
|
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(&DefLabel(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 {
|
|
// FIXME(#5275): this shouldn't have to be a method...
|
|
self.last_loop_scope()
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn last_loop_scope(&self) -> NodeId {
|
|
let loop_scope = &mut *self.loop_scope;
|
|
*loop_scope.last()
|
|
}
|
|
|
|
pub fn ln_str(&self, ln: LiveNode) -> ~str {
|
|
str::from_utf8_owned(io::mem::with_mem_writer(|wr| {
|
|
let wr = wr as &mut io::Writer;
|
|
write!(wr, "[ln({}) of kind {:?} reads", *ln, self.ir.lnks[*ln]);
|
|
self.write_vars(wr, ln, |idx| self.users[idx].reader );
|
|
write!(wr, " writes");
|
|
self.write_vars(wr, ln, |idx| self.users[idx].writer );
|
|
write!(wr, " precedes {}]", self.successors[*ln].to_str());
|
|
}))
|
|
}
|
|
|
|
pub fn init_empty(&self, 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();
|
|
// }
|
|
}
|
|
|
|
pub fn init_from_succ(&self, 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={}, succ={})",
|
|
self.ln_str(ln), self.ln_str(succ_ln));
|
|
}
|
|
|
|
pub fn merge_from_succ(&self,
|
|
ln: LiveNode,
|
|
succ_ln: LiveNode,
|
|
first_merge: bool)
|
|
-> bool {
|
|
if ln == succ_ln { return false; }
|
|
|
|
let mut changed = false;
|
|
self.indices2(ln, succ_ln, |idx, succ_idx| {
|
|
let users = &mut *self.users;
|
|
changed |= copy_if_invalid(users[succ_idx].reader,
|
|
&mut users[idx].reader);
|
|
changed |= copy_if_invalid(users[succ_idx].writer,
|
|
&mut users[idx].writer);
|
|
if users[succ_idx].used && !users[idx].used {
|
|
users[idx].used = true;
|
|
changed = true;
|
|
}
|
|
});
|
|
|
|
debug!("merge_from_succ(ln={}, succ={}, first_merge={}, changed={})",
|
|
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.
|
|
pub fn define(&self, writer: LiveNode, var: Variable) {
|
|
let idx = self.idx(writer, var);
|
|
self.users[idx].reader = invalid_node();
|
|
self.users[idx].writer = invalid_node();
|
|
|
|
debug!("{} defines {} (idx={}): {}", writer.to_str(), var.to_str(),
|
|
idx, self.ln_str(writer));
|
|
}
|
|
|
|
// Either read, write, or both depending on the acc bitset
|
|
pub fn acc(&self, ln: LiveNode, var: Variable, acc: uint) {
|
|
let idx = self.idx(ln, var);
|
|
let users = &mut *self.users;
|
|
let user = &mut 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 {
|
|
user.used = true;
|
|
}
|
|
|
|
debug!("{} accesses[{:x}] {}: {}",
|
|
ln.to_str(), acc, var.to_str(), self.ln_str(ln));
|
|
}
|
|
|
|
// _______________________________________________________________________
|
|
|
|
pub fn compute(&self, decl: &fn_decl, body: &Block) -> 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, {}", block_to_str(body,
|
|
self.tcx.sess.intr()));
|
|
|
|
let entry_ln: LiveNode =
|
|
self.with_loop_nodes(body.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 {} (entry={})",
|
|
{
|
|
for ln_idx in range(0u, self.ir.num_live_nodes) {
|
|
debug!("{}", self.ln_str(LiveNode(ln_idx)));
|
|
}
|
|
body.id
|
|
},
|
|
entry_ln.to_str());
|
|
|
|
entry_ln
|
|
}
|
|
|
|
pub fn propagate_through_fn_block(&self, _: &fn_decl, blk: &Block)
|
|
-> LiveNode {
|
|
// 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.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)
|
|
}
|
|
|
|
pub fn propagate_through_block(&self, blk: &Block, succ: LiveNode)
|
|
-> LiveNode {
|
|
let succ = self.propagate_through_opt_expr(blk.expr, succ);
|
|
blk.stmts.rev_iter().fold(succ, |succ, stmt| {
|
|
self.propagate_through_stmt(*stmt, succ)
|
|
})
|
|
}
|
|
|
|
pub fn propagate_through_stmt(&self, stmt: &Stmt, succ: LiveNode)
|
|
-> LiveNode {
|
|
match stmt.node {
|
|
StmtDecl(decl, _) => {
|
|
return self.propagate_through_decl(decl, succ);
|
|
}
|
|
|
|
StmtExpr(expr, _) | StmtSemi(expr, _) => {
|
|
return self.propagate_through_expr(expr, succ);
|
|
}
|
|
|
|
StmtMac(..) => {
|
|
self.tcx.sess.span_bug(stmt.span, "unexpanded macro");
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn propagate_through_decl(&self, decl: &Decl, succ: LiveNode)
|
|
-> LiveNode {
|
|
match decl.node {
|
|
DeclLocal(ref local) => {
|
|
self.propagate_through_local(*local, succ)
|
|
}
|
|
DeclItem(_) => succ,
|
|
}
|
|
}
|
|
|
|
pub fn propagate_through_local(&self, 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.init, succ);
|
|
self.define_bindings_in_pat(local.pat, succ)
|
|
}
|
|
|
|
pub fn propagate_through_exprs(&self, exprs: &[@Expr], succ: LiveNode)
|
|
-> LiveNode {
|
|
exprs.rev_iter().fold(succ, |succ, expr| {
|
|
self.propagate_through_expr(*expr, succ)
|
|
})
|
|
}
|
|
|
|
pub fn propagate_through_opt_expr(&self,
|
|
opt_expr: Option<@Expr>,
|
|
succ: LiveNode)
|
|
-> LiveNode {
|
|
opt_expr.iter().fold(succ, |succ, expr| {
|
|
self.propagate_through_expr(*expr, succ)
|
|
})
|
|
}
|
|
|
|
pub fn propagate_through_expr(&self, expr: @Expr, succ: LiveNode)
|
|
-> LiveNode {
|
|
debug!("propagate_through_expr: {}",
|
|
expr_to_str(expr, self.tcx.sess.intr()));
|
|
|
|
match expr.node {
|
|
// Interesting cases with control flow or which gen/kill
|
|
|
|
ExprPath(_) | ExprSelf => {
|
|
self.access_path(expr, succ, ACC_READ | ACC_USE)
|
|
}
|
|
|
|
ExprField(e, _, _) => {
|
|
self.propagate_through_expr(e, succ)
|
|
}
|
|
|
|
ExprFnBlock(_, blk) | ExprProc(_, blk) => {
|
|
debug!("{} is an ExprFnBlock or ExprProc",
|
|
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.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);
|
|
caps.rev_iter().fold(succ, |succ, cap| {
|
|
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
|
|
})
|
|
})
|
|
}
|
|
|
|
ExprIf(cond, 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)
|
|
}
|
|
|
|
ExprWhile(cond, blk) => {
|
|
self.propagate_through_loop(expr, Some(cond), blk, succ)
|
|
}
|
|
|
|
ExprForLoop(..) => fail!("non-desugared expr_for_loop"),
|
|
|
|
// Note that labels have been resolved, so we don't need to look
|
|
// at the label ident
|
|
ExprLoop(blk, _) => {
|
|
self.propagate_through_loop(expr, None, blk, succ)
|
|
}
|
|
|
|
ExprMatch(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 arm in arms.iter() {
|
|
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)
|
|
}
|
|
|
|
ExprRet(o_e) => {
|
|
// ignore succ and subst exit_ln:
|
|
self.propagate_through_opt_expr(o_e, self.s.exit_ln)
|
|
}
|
|
|
|
ExprBreak(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")
|
|
}
|
|
}
|
|
|
|
ExprAgain(opt_label) => {
|
|
// Find which label this expr continues 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")
|
|
}
|
|
}
|
|
|
|
ExprAssign(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)
|
|
}
|
|
|
|
ExprAssignOp(_, _, 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
|
|
|
|
ExprVstore(expr, _) => {
|
|
self.propagate_through_expr(expr, succ)
|
|
}
|
|
|
|
ExprVec(ref exprs, _) => {
|
|
self.propagate_through_exprs(*exprs, succ)
|
|
}
|
|
|
|
ExprRepeat(element, count, _) => {
|
|
let succ = self.propagate_through_expr(count, succ);
|
|
self.propagate_through_expr(element, succ)
|
|
}
|
|
|
|
ExprStruct(_, ref fields, with_expr) => {
|
|
let succ = self.propagate_through_opt_expr(with_expr, succ);
|
|
fields.rev_iter().fold(succ, |succ, field| {
|
|
self.propagate_through_expr(field.expr, succ)
|
|
})
|
|
}
|
|
|
|
ExprCall(f, ref 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)
|
|
}
|
|
|
|
ExprMethodCall(callee_id, rcvr, _, _, ref 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, 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)
|
|
}
|
|
|
|
ExprTup(ref exprs) => {
|
|
self.propagate_through_exprs(*exprs, succ)
|
|
}
|
|
|
|
ExprBinary(_, 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)
|
|
}
|
|
|
|
ExprIndex(_, l, r) |
|
|
ExprBinary(_, _, l, r) => {
|
|
self.propagate_through_exprs([l, r], succ)
|
|
}
|
|
|
|
ExprAddrOf(_, e) |
|
|
ExprDoBody(e) |
|
|
ExprCast(e, _) |
|
|
ExprUnary(_, _, e) |
|
|
ExprParen(e) => {
|
|
self.propagate_through_expr(e, succ)
|
|
}
|
|
|
|
ExprInlineAsm(ref ia) => {
|
|
let succ = ia.inputs.rev_iter().fold(succ, |succ, &(_, expr)| {
|
|
self.propagate_through_expr(expr, succ)
|
|
});
|
|
ia.outputs.rev_iter().fold(succ, |succ, &(_, expr)| {
|
|
// see comment on lvalues in
|
|
// propagate_through_lvalue_components()
|
|
let succ = self.write_lvalue(expr, succ, ACC_WRITE);
|
|
self.propagate_through_lvalue_components(expr, succ)
|
|
})
|
|
}
|
|
|
|
ExprLogLevel |
|
|
ExprLit(..) => {
|
|
succ
|
|
}
|
|
|
|
ExprBlock(blk) => {
|
|
self.propagate_through_block(blk, succ)
|
|
}
|
|
|
|
ExprMac(..) => {
|
|
self.tcx.sess.span_bug(expr.span, "unexpanded macro");
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn propagate_through_lvalue_components(&self,
|
|
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 {
|
|
ExprPath(_) => succ,
|
|
ExprField(e, _, _) => self.propagate_through_expr(e, succ),
|
|
_ => self.propagate_through_expr(expr, succ)
|
|
}
|
|
}
|
|
|
|
// see comment on propagate_through_lvalue()
|
|
pub fn write_lvalue(&self, expr: &Expr, succ: LiveNode, acc: uint)
|
|
-> LiveNode {
|
|
match expr.node {
|
|
ExprPath(_) => 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
|
|
}
|
|
}
|
|
|
|
pub fn access_path(&self, expr: &Expr, succ: LiveNode, acc: uint)
|
|
-> LiveNode {
|
|
let def = self.tcx.def_map.get_copy(&expr.id);
|
|
match moves::moved_variable_node_id_from_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
|
|
}
|
|
}
|
|
|
|
pub fn propagate_through_loop(&self,
|
|
expr: &Expr,
|
|
cond: Option<@Expr>,
|
|
body: &Block,
|
|
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 {} {}",
|
|
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
|
|
}
|
|
|
|
pub fn with_loop_nodes<R>(
|
|
&self,
|
|
loop_node_id: NodeId,
|
|
break_ln: LiveNode,
|
|
cont_ln: LiveNode,
|
|
f: || -> R)
|
|
-> R {
|
|
debug!("with_loop_nodes: {} {}", 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();
|
|
r
|
|
}
|
|
}
|
|
|
|
// _______________________________________________________________________
|
|
// Checking for error conditions
|
|
|
|
fn check_local(this: &mut Liveness, local: @Local) {
|
|
match local.init {
|
|
Some(_) => {
|
|
this.warn_about_unused_or_dead_vars_in_pat(local.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");
|
|
this.pat_bindings(local.pat, |ln, var, sp, id| {
|
|
if !this.warn_about_unused(sp, id, ln, var) {
|
|
match this.live_on_exit(ln, var) {
|
|
None => { /* not live: good */ }
|
|
Some(lnk) => {
|
|
this.report_illegal_read(
|
|
local.span, lnk, var,
|
|
PossiblyUninitializedVariable);
|
|
}
|
|
}
|
|
}
|
|
})
|
|
}
|
|
}
|
|
|
|
visit::walk_local(this, local, ());
|
|
}
|
|
|
|
fn check_arm(this: &mut Liveness, arm: &Arm) {
|
|
this.arm_pats_bindings(arm.pats, |ln, var, sp, id| {
|
|
this.warn_about_unused(sp, id, ln, var);
|
|
});
|
|
visit::walk_arm(this, arm, ());
|
|
}
|
|
|
|
fn check_expr(this: &mut Liveness, expr: @Expr) {
|
|
match expr.node {
|
|
ExprAssign(l, r) => {
|
|
this.check_lvalue(l);
|
|
this.visit_expr(r, ());
|
|
|
|
visit::walk_expr(this, expr, ());
|
|
}
|
|
|
|
ExprAssignOp(_, _, l, _) => {
|
|
this.check_lvalue(l);
|
|
|
|
visit::walk_expr(this, expr, ());
|
|
}
|
|
|
|
ExprInlineAsm(ref ia) => {
|
|
for &(_, input) in ia.inputs.iter() {
|
|
this.visit_expr(input, ());
|
|
}
|
|
|
|
// Output operands must be lvalues
|
|
for &(_, out) in ia.outputs.iter() {
|
|
this.check_lvalue(out);
|
|
this.visit_expr(out, ());
|
|
}
|
|
|
|
visit::walk_expr(this, expr, ());
|
|
}
|
|
|
|
// no correctness conditions related to liveness
|
|
ExprCall(..) | ExprMethodCall(..) | ExprIf(..) | ExprMatch(..) |
|
|
ExprWhile(..) | ExprLoop(..) | ExprIndex(..) | ExprField(..) |
|
|
ExprVstore(..) | ExprVec(..) | ExprTup(..) | ExprLogLevel |
|
|
ExprBinary(..) | ExprDoBody(..) |
|
|
ExprCast(..) | ExprUnary(..) | ExprRet(..) | ExprBreak(..) |
|
|
ExprAgain(..) | ExprLit(_) | ExprBlock(..) |
|
|
ExprMac(..) | ExprAddrOf(..) | ExprStruct(..) | ExprRepeat(..) |
|
|
ExprParen(..) | ExprFnBlock(..) | ExprProc(..) | ExprPath(..) |
|
|
ExprSelf(..) => {
|
|
visit::walk_expr(this, expr, ());
|
|
}
|
|
ExprForLoop(..) => fail!("non-desugared expr_for_loop")
|
|
}
|
|
}
|
|
|
|
fn check_fn(_v: &Liveness,
|
|
_fk: &visit::fn_kind,
|
|
_decl: &fn_decl,
|
|
_body: &Block,
|
|
_sp: Span,
|
|
_id: NodeId) {
|
|
// do not check contents of nested fns
|
|
}
|
|
|
|
enum ReadKind {
|
|
PossiblyUninitializedVariable,
|
|
PossiblyUninitializedField,
|
|
MovedValue,
|
|
PartiallyMovedValue
|
|
}
|
|
|
|
impl Liveness {
|
|
pub fn check_ret(&self,
|
|
id: NodeId,
|
|
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");
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn check_lvalue(&mut self, expr: @Expr) {
|
|
match expr.node {
|
|
ExprPath(_) => {
|
|
match self.tcx.def_map.get_copy(&expr.id) {
|
|
DefLocal(nid, _) => {
|
|
// Assignment to an immutable variable or argument: only legal
|
|
// if there is no later assignment. If this local is actually
|
|
// mutable, then check for a reassignment to flag the mutability
|
|
// as being used.
|
|
let ln = self.live_node(expr.id, expr.span);
|
|
let var = self.variable(nid, expr.span);
|
|
self.warn_about_dead_assign(expr.span, expr.id, ln, var);
|
|
}
|
|
def => {
|
|
match moves::moved_variable_node_id_from_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, expr.id, ln, var);
|
|
}
|
|
None => {}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
_ => {
|
|
// For other kinds of lvalues, no checks are required,
|
|
// and any embedded expressions are actually rvalues
|
|
visit::walk_expr(self, expr, ());
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn report_illegal_read(&self,
|
|
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,
|
|
format!("capture of {}: `{}`", msg, name));
|
|
}
|
|
ExprNode(span) => {
|
|
self.tcx.sess.span_err(
|
|
span,
|
|
format!("use of {}: `{}`", msg, name));
|
|
}
|
|
ExitNode | VarDefNode(_) => {
|
|
self.tcx.sess.span_bug(
|
|
chk_span,
|
|
format!("illegal reader: {:?}", lnk));
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn should_warn(&self, var: Variable) -> Option<@str> {
|
|
let name = self.ir.variable_name(var);
|
|
if name.len() == 0 || name[0] == ('_' as u8) { None } else { Some(name) }
|
|
}
|
|
|
|
pub fn warn_about_unused_args(&self, decl: &fn_decl, entry_ln: LiveNode) {
|
|
for arg in decl.inputs.iter() {
|
|
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, p_id, entry_ln, var);
|
|
})
|
|
}
|
|
}
|
|
|
|
pub fn warn_about_unused_or_dead_vars_in_pat(&self, pat: @Pat) {
|
|
self.pat_bindings(pat, |ln, var, sp, id| {
|
|
if !self.warn_about_unused(sp, id, ln, var) {
|
|
self.warn_about_dead_assign(sp, id, ln, var);
|
|
}
|
|
})
|
|
}
|
|
|
|
pub fn warn_about_unused(&self,
|
|
sp: Span,
|
|
id: NodeId,
|
|
ln: LiveNode,
|
|
var: Variable)
|
|
-> bool {
|
|
if !self.used_on_entry(ln, var) {
|
|
let r = self.should_warn(var);
|
|
for name in r.iter() {
|
|
|
|
// 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 {
|
|
self.tcx.sess.add_lint(unused_variable, id, sp,
|
|
format!("variable `{}` is assigned to, \
|
|
but never used", *name));
|
|
} else {
|
|
self.tcx.sess.add_lint(unused_variable, id, sp,
|
|
format!("unused variable: `{}`", *name));
|
|
}
|
|
}
|
|
true
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
pub fn warn_about_dead_assign(&self,
|
|
sp: Span,
|
|
id: NodeId,
|
|
ln: LiveNode,
|
|
var: Variable) {
|
|
if self.live_on_exit(ln, var).is_none() {
|
|
let r = self.should_warn(var);
|
|
for name in r.iter() {
|
|
self.tcx.sess.add_lint(dead_assignment, id, sp,
|
|
format!("value assigned to `{}` is never read", *name));
|
|
}
|
|
}
|
|
}
|
|
}
|