rust/src/librustc/middle/dataflow.rs
Patrick Walton cc0584731a librustc: De-@mut the def map.
This is the last `@mut` in `librustc` that does not depend on libsyntax.
2013-12-26 15:54:37 -08:00

1019 lines
36 KiB
Rust

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/*!
* A module for propagating forward dataflow information. The analysis
* assumes that the items to be propagated can be represented as bits
* and thus uses bitvectors. Your job is simply to specify the so-called
* GEN and KILL bits for each expression.
*/
use std::cast;
use std::io;
use std::uint;
use std::vec;
use std::hashmap::HashMap;
use syntax::ast;
use syntax::ast_util;
use syntax::ast_util::id_range;
use syntax::print::{pp, pprust};
use middle::ty;
use middle::typeck;
use util::ppaux::Repr;
#[deriving(Clone)]
pub struct DataFlowContext<O> {
priv tcx: ty::ctxt,
priv method_map: typeck::method_map,
/// the data flow operator
priv oper: O,
/// number of bits to propagate per id
priv bits_per_id: uint,
/// number of words we will use to store bits_per_id.
/// equal to bits_per_id/uint::bits rounded up.
priv words_per_id: uint,
// mapping from node to bitset index.
priv nodeid_to_bitset: HashMap<ast::NodeId,uint>,
// Bit sets per id. The following three fields (`gens`, `kills`,
// and `on_entry`) all have the same structure. For each id in
// `id_range`, there is a range of words equal to `words_per_id`.
// So, to access the bits for any given id, you take a slice of
// the full vector (see the method `compute_id_range()`).
/// bits generated as we exit the scope `id`. Updated by `add_gen()`.
priv gens: ~[uint],
/// bits killed as we exit the scope `id`. Updated by `add_kill()`.
priv kills: ~[uint],
/// bits that are valid on entry to the scope `id`. Updated by
/// `propagate()`.
priv on_entry: ~[uint]
}
/// Parameterization for the precise form of data flow that is used.
pub trait DataFlowOperator {
/// Specifies the initial value for each bit in the `on_entry` set
fn initial_value(&self) -> bool;
/// Joins two predecessor bits together, typically either `|` or `&`
fn join(&self, succ: uint, pred: uint) -> uint;
/// True if we should propagate through closures
fn walk_closures(&self) -> bool;
}
struct PropagationContext<'a, O> {
dfcx: &'a mut DataFlowContext<O>,
changed: bool
}
struct LoopScope<'a> {
loop_id: ast::NodeId,
break_bits: ~[uint]
}
impl<O:DataFlowOperator> pprust::pp_ann for DataFlowContext<O> {
fn pre(&self, node: pprust::ann_node) {
let (ps, id) = match node {
pprust::node_expr(ps, expr) => (ps, expr.id),
pprust::node_block(ps, blk) => (ps, blk.id),
pprust::node_item(ps, _) => (ps, 0),
pprust::node_pat(ps, pat) => (ps, pat.id)
};
if self.nodeid_to_bitset.contains_key(&id) {
let (start, end) = self.compute_id_range_frozen(id);
let on_entry = self.on_entry.slice(start, end);
let entry_str = bits_to_str(on_entry);
let gens = self.gens.slice(start, end);
let gens_str = if gens.iter().any(|&u| u != 0) {
format!(" gen: {}", bits_to_str(gens))
} else {
~""
};
let kills = self.kills.slice(start, end);
let kills_str = if kills.iter().any(|&u| u != 0) {
format!(" kill: {}", bits_to_str(kills))
} else {
~""
};
let comment_str = format!("id {}: {}{}{}",
id, entry_str, gens_str, kills_str);
pprust::synth_comment(ps, comment_str);
pp::space(ps.s);
}
}
}
impl<O:DataFlowOperator> DataFlowContext<O> {
pub fn new(tcx: ty::ctxt,
method_map: typeck::method_map,
oper: O,
id_range: id_range,
bits_per_id: uint) -> DataFlowContext<O> {
let words_per_id = (bits_per_id + uint::bits - 1) / uint::bits;
debug!("DataFlowContext::new(id_range={:?}, bits_per_id={:?}, words_per_id={:?})",
id_range, bits_per_id, words_per_id);
let gens = ~[];
let kills = ~[];
let on_entry = ~[];
DataFlowContext {
tcx: tcx,
method_map: method_map,
words_per_id: words_per_id,
nodeid_to_bitset: HashMap::new(),
bits_per_id: bits_per_id,
oper: oper,
gens: gens,
kills: kills,
on_entry: on_entry
}
}
pub fn add_gen(&mut self, id: ast::NodeId, bit: uint) {
//! Indicates that `id` generates `bit`
debug!("add_gen(id={:?}, bit={:?})", id, bit);
let (start, end) = self.compute_id_range(id);
{
let gens = self.gens.mut_slice(start, end);
set_bit(gens, bit);
}
}
pub fn add_kill(&mut self, id: ast::NodeId, bit: uint) {
//! Indicates that `id` kills `bit`
debug!("add_kill(id={:?}, bit={:?})", id, bit);
let (start, end) = self.compute_id_range(id);
{
let kills = self.kills.mut_slice(start, end);
set_bit(kills, bit);
}
}
fn apply_gen_kill(&mut self, id: ast::NodeId, bits: &mut [uint]) {
//! Applies the gen and kill sets for `id` to `bits`
debug!("apply_gen_kill(id={:?}, bits={}) [before]",
id, mut_bits_to_str(bits));
let (start, end) = self.compute_id_range(id);
let gens = self.gens.slice(start, end);
bitwise(bits, gens, |a, b| a | b);
let kills = self.kills.slice(start, end);
bitwise(bits, kills, |a, b| a & !b);
debug!("apply_gen_kill(id={:?}, bits={}) [after]",
id, mut_bits_to_str(bits));
}
fn apply_kill(&mut self, id: ast::NodeId, bits: &mut [uint]) {
debug!("apply_kill(id={:?}, bits={}) [before]",
id, mut_bits_to_str(bits));
let (start, end) = self.compute_id_range(id);
let kills = self.kills.slice(start, end);
bitwise(bits, kills, |a, b| a & !b);
debug!("apply_kill(id={:?}, bits={}) [after]",
id, mut_bits_to_str(bits));
}
fn compute_id_range_frozen(&self, id: ast::NodeId) -> (uint, uint) {
let n = *self.nodeid_to_bitset.get(&id);
let start = n * self.words_per_id;
let end = start + self.words_per_id;
(start, end)
}
fn compute_id_range(&mut self, id: ast::NodeId) -> (uint, uint) {
let mut expanded = false;
let len = self.nodeid_to_bitset.len();
let n = self.nodeid_to_bitset.find_or_insert_with(id, |_| {
expanded = true;
len
});
if expanded {
let entry = if self.oper.initial_value() { uint::max_value } else {0};
self.words_per_id.times(|| {
self.gens.push(0);
self.kills.push(0);
self.on_entry.push(entry);
})
}
let start = *n * self.words_per_id;
let end = start + self.words_per_id;
assert!(start < self.gens.len());
assert!(end <= self.gens.len());
assert!(self.gens.len() == self.kills.len());
assert!(self.gens.len() == self.on_entry.len());
(start, end)
}
pub fn each_bit_on_entry_frozen(&self,
id: ast::NodeId,
f: |uint| -> bool)
-> bool {
//! Iterates through each bit that is set on entry to `id`.
//! Only useful after `propagate()` has been called.
if !self.nodeid_to_bitset.contains_key(&id) {
return true;
}
let (start, end) = self.compute_id_range_frozen(id);
let on_entry = self.on_entry.slice(start, end);
debug!("each_bit_on_entry_frozen(id={:?}, on_entry={})",
id, bits_to_str(on_entry));
self.each_bit(on_entry, f)
}
pub fn each_bit_on_entry(&mut self,
id: ast::NodeId,
f: |uint| -> bool)
-> bool {
//! Iterates through each bit that is set on entry to `id`.
//! Only useful after `propagate()` has been called.
let (start, end) = self.compute_id_range(id);
let on_entry = self.on_entry.slice(start, end);
debug!("each_bit_on_entry(id={:?}, on_entry={})",
id, bits_to_str(on_entry));
self.each_bit(on_entry, f)
}
pub fn each_gen_bit(&mut self, id: ast::NodeId, f: |uint| -> bool)
-> bool {
//! Iterates through each bit in the gen set for `id`.
let (start, end) = self.compute_id_range(id);
let gens = self.gens.slice(start, end);
debug!("each_gen_bit(id={:?}, gens={})",
id, bits_to_str(gens));
self.each_bit(gens, f)
}
pub fn each_gen_bit_frozen(&self, id: ast::NodeId, f: |uint| -> bool)
-> bool {
//! Iterates through each bit in the gen set for `id`.
if !self.nodeid_to_bitset.contains_key(&id) {
return true;
}
let (start, end) = self.compute_id_range_frozen(id);
let gens = self.gens.slice(start, end);
debug!("each_gen_bit(id={:?}, gens={})",
id, bits_to_str(gens));
self.each_bit(gens, f)
}
fn each_bit(&self, words: &[uint], f: |uint| -> bool) -> bool {
//! Helper for iterating over the bits in a bit set.
for (word_index, &word) in words.iter().enumerate() {
if word != 0 {
let base_index = word_index * uint::bits;
for offset in range(0u, uint::bits) {
let bit = 1 << offset;
if (word & bit) != 0 {
// NB: we round up the total number of bits
// that we store in any given bit set so that
// it is an even multiple of uint::bits. This
// means that there may be some stray bits at
// the end that do not correspond to any
// actual value. So before we callback, check
// whether the bit_index is greater than the
// actual value the user specified and stop
// iterating if so.
let bit_index = base_index + offset;
if bit_index >= self.bits_per_id {
return true;
} else if !f(bit_index) {
return false;
}
}
}
}
}
return true;
}
}
impl<O:DataFlowOperator+Clone+'static> DataFlowContext<O> {
// ^^^^^^^^^^^^^ only needed for pretty printing
pub fn propagate(&mut self, blk: &ast::Block) {
//! Performs the data flow analysis.
if self.bits_per_id == 0 {
// Optimize the surprisingly common degenerate case.
return;
}
{
let mut propcx = PropagationContext {
dfcx: self,
changed: true
};
let mut temp = vec::from_elem(self.words_per_id, 0u);
let mut loop_scopes = ~[];
while propcx.changed {
propcx.changed = false;
propcx.reset(temp);
propcx.walk_block(blk, temp, &mut loop_scopes);
}
}
debug!("Dataflow result:");
debug!("{}", {
let this = @(*self).clone();
this.pretty_print_to(@mut io::stderr() as @mut io::Writer, blk);
""
});
}
fn pretty_print_to(@self, wr: @mut io::Writer, blk: &ast::Block) {
let ps = pprust::rust_printer_annotated(wr,
self.tcx.sess.intr(),
self as @pprust::pp_ann);
pprust::cbox(ps, pprust::indent_unit);
pprust::ibox(ps, 0u);
pprust::print_block(ps, blk);
pp::eof(ps.s);
}
}
impl<'a, O:DataFlowOperator> PropagationContext<'a, O> {
fn tcx(&self) -> ty::ctxt {
self.dfcx.tcx
}
fn walk_block(&mut self,
blk: &ast::Block,
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
debug!("DataFlowContext::walk_block(blk.id={:?}, in_out={})",
blk.id, bits_to_str(reslice(in_out)));
self.merge_with_entry_set(blk.id, in_out);
for &stmt in blk.stmts.iter() {
self.walk_stmt(stmt, in_out, loop_scopes);
}
self.walk_opt_expr(blk.expr, in_out, loop_scopes);
self.dfcx.apply_gen_kill(blk.id, in_out);
}
fn walk_stmt(&mut self,
stmt: @ast::Stmt,
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
match stmt.node {
ast::StmtDecl(decl, _) => {
self.walk_decl(decl, in_out, loop_scopes);
}
ast::StmtExpr(expr, _) | ast::StmtSemi(expr, _) => {
self.walk_expr(expr, in_out, loop_scopes);
}
ast::StmtMac(..) => {
self.tcx().sess.span_bug(stmt.span, "unexpanded macro");
}
}
}
fn walk_decl(&mut self,
decl: @ast::Decl,
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
match decl.node {
ast::DeclLocal(local) => {
self.walk_opt_expr(local.init, in_out, loop_scopes);
self.walk_pat(local.pat, in_out, loop_scopes);
}
ast::DeclItem(_) => {}
}
}
fn walk_expr(&mut self,
expr: &ast::Expr,
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
debug!("DataFlowContext::walk_expr(expr={}, in_out={})",
expr.repr(self.dfcx.tcx), bits_to_str(reslice(in_out)));
self.merge_with_entry_set(expr.id, in_out);
match expr.node {
ast::ExprFnBlock(ref decl, body) |
ast::ExprProc(ref decl, body) => {
if self.dfcx.oper.walk_closures() {
// In the absence of once fns, we must assume that
// every function body will execute more than
// once. Thus we treat every function body like a
// loop.
//
// What is subtle and a bit tricky, also, is how
// to deal with the "output" bits---that is, what
// do we consider to be the successor of a
// function body, given that it could be called
// from any point within its lifetime? What we do
// is to add their effects immediately as of the
// point of creation. Of course we have to ensure
// that this is sound for the analyses which make
// use of dataflow.
//
// In the case of the initedness checker (which
// does not currently use dataflow, but I hope to
// convert at some point), we will simply not walk
// closures at all, so it's a moot point.
//
// In the case of the borrow checker, this means
// the loans which would be created by calling a
// function come into effect immediately when the
// function is created. This is guaranteed to be
// earlier than the point at which the loan
// actually comes into scope (which is the point
// at which the closure is *called*). Because
// loans persist until the scope of the loans is
// exited, it is always a safe approximation to
// have a loan begin earlier than it actually will
// at runtime, so this should be sound.
//
// We stil have to be careful in the region
// checker and borrow checker to treat function
// bodies like loops, which implies some
// limitations. For example, a closure cannot root
// a managed box for longer than its body.
//
// General control flow looks like this:
//
// +- (expr) <----------+
// | | |
// | v |
// | (body) -----------+--> (exit)
// | | |
// | + (break/loop) -+
// | |
// +--------------------+
//
// This is a bit more conservative than a loop.
// Note that we must assume that even after a
// `break` occurs (e.g., in a `for` loop) that the
// closure may be reinvoked.
//
// One difference from other loops is that `loop`
// and `break` statements which target a closure
// both simply add to the `break_bits`.
// func_bits represents the state when the function
// returns
let mut func_bits = reslice(in_out).to_owned();
loop_scopes.push(LoopScope {
loop_id: expr.id,
break_bits: reslice(in_out).to_owned()
});
for input in decl.inputs.iter() {
self.walk_pat(input.pat, func_bits, loop_scopes);
}
self.walk_block(body, func_bits, loop_scopes);
// add the bits from any early return via `break`,
// `continue`, or `return` into `func_bits`
let loop_scope = loop_scopes.pop();
join_bits(&self.dfcx.oper, loop_scope.break_bits, func_bits);
// add `func_bits` to the entry bits for `expr`,
// since we must assume the function may be called
// more than once
self.add_to_entry_set(expr.id, reslice(func_bits));
// the final exit bits include whatever was present
// in the original, joined with the bits from the function
join_bits(&self.dfcx.oper, func_bits, in_out);
}
}
ast::ExprIf(cond, then, els) => {
//
// (cond)
// |
// v
// ( )
// / \
// | |
// v v
// (then)(els)
// | |
// v v
// ( succ )
//
self.walk_expr(cond, in_out, loop_scopes);
let mut then_bits = reslice(in_out).to_owned();
self.walk_block(then, then_bits, loop_scopes);
self.walk_opt_expr(els, in_out, loop_scopes);
join_bits(&self.dfcx.oper, then_bits, in_out);
}
ast::ExprWhile(cond, blk) => {
//
// (expr) <--+
// | |
// v |
// +--(cond) |
// | | |
// | v |
// v (blk) ----+
// |
// <--+ (break)
//
self.walk_expr(cond, in_out, loop_scopes);
let mut body_bits = reslice(in_out).to_owned();
loop_scopes.push(LoopScope {
loop_id: expr.id,
break_bits: reslice(in_out).to_owned()
});
self.walk_block(blk, body_bits, loop_scopes);
self.add_to_entry_set(expr.id, body_bits);
let new_loop_scope = loop_scopes.pop();
copy_bits(new_loop_scope.break_bits, in_out);
}
ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop"),
ast::ExprLoop(blk, _) => {
//
// (expr) <--+
// | |
// v |
// (blk) ----+
// |
// <--+ (break)
//
let mut body_bits = reslice(in_out).to_owned();
self.reset(in_out);
loop_scopes.push(LoopScope {
loop_id: expr.id,
break_bits: reslice(in_out).to_owned()
});
self.walk_block(blk, body_bits, loop_scopes);
self.add_to_entry_set(expr.id, body_bits);
let new_loop_scope = loop_scopes.pop();
assert_eq!(new_loop_scope.loop_id, expr.id);
copy_bits(new_loop_scope.break_bits, in_out);
}
ast::ExprMatch(discr, ref arms) => {
//
// (discr)
// / | \
// | | |
// v v v
// (..arms..)
// | | |
// v v v
// ( succ )
//
//
self.walk_expr(discr, in_out, loop_scopes);
let mut guards = reslice(in_out).to_owned();
// We know that exactly one arm will be taken, so we
// can start out with a blank slate and just union
// together the bits from each arm:
self.reset(in_out);
for arm in arms.iter() {
// in_out reflects the discr and all guards to date
self.walk_opt_expr(arm.guard, guards, loop_scopes);
// determine the bits for the body and then union
// them into `in_out`, which reflects all bodies to date
let mut body = reslice(guards).to_owned();
self.walk_pat_alternatives(arm.pats, body, loop_scopes);
self.walk_block(arm.body, body, loop_scopes);
join_bits(&self.dfcx.oper, body, in_out);
}
}
ast::ExprRet(o_e) => {
self.walk_opt_expr(o_e, in_out, loop_scopes);
self.reset(in_out);
}
ast::ExprBreak(label) => {
let scope = self.find_scope(expr, label, loop_scopes);
self.break_from_to(expr, scope, in_out);
self.reset(in_out);
}
ast::ExprAgain(label) => {
let scope = self.find_scope(expr, label, loop_scopes);
self.pop_scopes(expr, scope, in_out);
self.add_to_entry_set(scope.loop_id, reslice(in_out));
self.reset(in_out);
}
ast::ExprAssign(l, r) |
ast::ExprAssignOp(_, _, l, r) => {
self.walk_expr(r, in_out, loop_scopes);
self.walk_expr(l, in_out, loop_scopes);
}
ast::ExprVec(ref exprs, _) => {
self.walk_exprs(*exprs, in_out, loop_scopes)
}
ast::ExprRepeat(l, r, _) => {
self.walk_expr(l, in_out, loop_scopes);
self.walk_expr(r, in_out, loop_scopes);
}
ast::ExprStruct(_, ref fields, with_expr) => {
for field in fields.iter() {
self.walk_expr(field.expr, in_out, loop_scopes);
}
self.walk_opt_expr(with_expr, in_out, loop_scopes);
}
ast::ExprCall(f, ref args, _) => {
self.walk_call(f.id, expr.id,
f, *args, in_out, loop_scopes);
}
ast::ExprMethodCall(callee_id, rcvr, _, _, ref args, _) => {
self.walk_call(callee_id, expr.id,
rcvr, *args, in_out, loop_scopes);
}
ast::ExprIndex(callee_id, l, r) |
ast::ExprBinary(callee_id, _, l, r) if self.is_method_call(expr) => {
self.walk_call(callee_id, expr.id,
l, [r], in_out, loop_scopes);
}
ast::ExprUnary(callee_id, _, e) if self.is_method_call(expr) => {
self.walk_call(callee_id, expr.id,
e, [], in_out, loop_scopes);
}
ast::ExprTup(ref exprs) => {
self.walk_exprs(*exprs, in_out, loop_scopes);
}
ast::ExprBinary(_, op, l, r) if ast_util::lazy_binop(op) => {
self.walk_expr(l, in_out, loop_scopes);
let temp = reslice(in_out).to_owned();
self.walk_expr(r, in_out, loop_scopes);
join_bits(&self.dfcx.oper, temp, in_out);
}
ast::ExprIndex(_, l, r) |
ast::ExprBinary(_, _, l, r) => {
self.walk_exprs([l, r], in_out, loop_scopes);
}
ast::ExprLogLevel |
ast::ExprLit(..) |
ast::ExprPath(..) |
ast::ExprSelf => {
}
ast::ExprAddrOf(_, e) |
ast::ExprDoBody(e) |
ast::ExprCast(e, _) |
ast::ExprUnary(_, _, e) |
ast::ExprParen(e) |
ast::ExprVstore(e, _) |
ast::ExprField(e, _, _) => {
self.walk_expr(e, in_out, loop_scopes);
}
ast::ExprInlineAsm(ref inline_asm) => {
for &(_, expr) in inline_asm.inputs.iter() {
self.walk_expr(expr, in_out, loop_scopes);
}
for &(_, expr) in inline_asm.outputs.iter() {
self.walk_expr(expr, in_out, loop_scopes);
}
}
ast::ExprBlock(blk) => {
self.walk_block(blk, in_out, loop_scopes);
}
ast::ExprMac(..) => {
self.tcx().sess.span_bug(expr.span, "unexpanded macro");
}
}
self.dfcx.apply_gen_kill(expr.id, in_out);
}
fn pop_scopes(&mut self,
from_expr: &ast::Expr,
to_scope: &mut LoopScope,
in_out: &mut [uint]) {
//! Whenever you have a `break` or a `loop` statement, flow
//! exits through any number of enclosing scopes on its
//! way to the new destination. This function applies the kill
//! sets of those enclosing scopes to `in_out` (those kill sets
//! concern items that are going out of scope).
let tcx = self.tcx();
let region_maps = tcx.region_maps;
debug!("pop_scopes(from_expr={}, to_scope={:?}, in_out={})",
from_expr.repr(tcx), to_scope.loop_id,
bits_to_str(reslice(in_out)));
let mut id = from_expr.id;
while id != to_scope.loop_id {
self.dfcx.apply_kill(id, in_out);
match region_maps.opt_encl_scope(id) {
Some(i) => { id = i; }
None => {
tcx.sess.span_bug(
from_expr.span,
format!("pop_scopes(from_expr={}, to_scope={:?}) \
to_scope does not enclose from_expr",
from_expr.repr(tcx), to_scope.loop_id));
}
}
}
}
fn break_from_to(&mut self,
from_expr: &ast::Expr,
to_scope: &mut LoopScope,
in_out: &mut [uint]) {
self.pop_scopes(from_expr, to_scope, in_out);
self.dfcx.apply_kill(from_expr.id, in_out);
join_bits(&self.dfcx.oper, reslice(in_out), to_scope.break_bits);
debug!("break_from_to(from_expr={}, to_scope={:?}) final break_bits={}",
from_expr.repr(self.tcx()),
to_scope.loop_id,
bits_to_str(reslice(in_out)));
}
fn walk_exprs(&mut self,
exprs: &[@ast::Expr],
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
for &expr in exprs.iter() {
self.walk_expr(expr, in_out, loop_scopes);
}
}
fn walk_opt_expr(&mut self,
opt_expr: Option<@ast::Expr>,
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
for &expr in opt_expr.iter() {
self.walk_expr(expr, in_out, loop_scopes);
}
}
fn walk_call(&mut self,
_callee_id: ast::NodeId,
call_id: ast::NodeId,
arg0: &ast::Expr,
args: &[@ast::Expr],
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
self.walk_expr(arg0, in_out, loop_scopes);
self.walk_exprs(args, in_out, loop_scopes);
// FIXME(#6268) nested method calls
// self.merge_with_entry_set(callee_id, in_out);
// self.dfcx.apply_gen_kill(callee_id, in_out);
let return_ty = ty::node_id_to_type(self.tcx(), call_id);
let fails = ty::type_is_bot(return_ty);
if fails {
self.reset(in_out);
}
}
fn walk_pat(&mut self,
pat: @ast::Pat,
in_out: &mut [uint],
_loop_scopes: &mut ~[LoopScope]) {
debug!("DataFlowContext::walk_pat(pat={}, in_out={})",
pat.repr(self.dfcx.tcx), bits_to_str(reslice(in_out)));
ast_util::walk_pat(pat, |p| {
debug!(" p.id={:?} in_out={}", p.id, bits_to_str(reslice(in_out)));
self.merge_with_entry_set(p.id, in_out);
self.dfcx.apply_gen_kill(p.id, in_out);
true
});
}
fn walk_pat_alternatives(&mut self,
pats: &[@ast::Pat],
in_out: &mut [uint],
loop_scopes: &mut ~[LoopScope]) {
if pats.len() == 1 {
// Common special case:
return self.walk_pat(pats[0], in_out, loop_scopes);
}
// In the general case, the patterns in `pats` are
// alternatives, so we must treat this like an N-way select
// statement.
let initial_state = reslice(in_out).to_owned();
for &pat in pats.iter() {
let mut temp = initial_state.clone();
self.walk_pat(pat, temp, loop_scopes);
join_bits(&self.dfcx.oper, temp, in_out);
}
}
fn find_scope<'a>(&self,
expr: &ast::Expr,
label: Option<ast::Name>,
loop_scopes: &'a mut ~[LoopScope]) -> &'a mut LoopScope {
let index = match label {
None => {
let len = loop_scopes.len();
len - 1
}
Some(_) => {
let def_map = self.tcx().def_map.borrow();
match def_map.get().find(&expr.id) {
Some(&ast::DefLabel(loop_id)) => {
match loop_scopes.iter().position(|l| l.loop_id == loop_id) {
Some(i) => i,
None => {
self.tcx().sess.span_bug(
expr.span,
format!("No loop scope for id {:?}", loop_id));
}
}
}
r => {
self.tcx().sess.span_bug(
expr.span,
format!("Bad entry `{:?}` in def_map for label", r));
}
}
}
};
&mut loop_scopes[index]
}
fn is_method_call(&self, expr: &ast::Expr) -> bool {
let method_map = self.dfcx.method_map.borrow();
method_map.get().contains_key(&expr.id)
}
fn reset(&mut self, bits: &mut [uint]) {
let e = if self.dfcx.oper.initial_value() {uint::max_value} else {0};
for b in bits.mut_iter() { *b = e; }
}
fn add_to_entry_set(&mut self, id: ast::NodeId, pred_bits: &[uint]) {
debug!("add_to_entry_set(id={:?}, pred_bits={})",
id, bits_to_str(pred_bits));
let (start, end) = self.dfcx.compute_id_range(id);
let changed = { // FIXME(#5074) awkward construction
let on_entry = self.dfcx.on_entry.mut_slice(start, end);
join_bits(&self.dfcx.oper, pred_bits, on_entry)
};
if changed {
debug!("changed entry set for {:?} to {}",
id, bits_to_str(self.dfcx.on_entry.slice(start, end)));
self.changed = true;
}
}
fn merge_with_entry_set(&mut self,
id: ast::NodeId,
pred_bits: &mut [uint]) {
debug!("merge_with_entry_set(id={:?}, pred_bits={})",
id, mut_bits_to_str(pred_bits));
let (start, end) = self.dfcx.compute_id_range(id);
let changed = { // FIXME(#5074) awkward construction
let on_entry = self.dfcx.on_entry.mut_slice(start, end);
let changed = join_bits(&self.dfcx.oper, reslice(pred_bits), on_entry);
copy_bits(reslice(on_entry), pred_bits);
changed
};
if changed {
debug!("changed entry set for {:?} to {}",
id, bits_to_str(self.dfcx.on_entry.slice(start, end)));
self.changed = true;
}
}
}
fn mut_bits_to_str(words: &mut [uint]) -> ~str {
bits_to_str(reslice(words))
}
fn bits_to_str(words: &[uint]) -> ~str {
let mut result = ~"";
let mut sep = '[';
// Note: this is a little endian printout of bytes.
for &word in words.iter() {
let mut v = word;
for _ in range(0u, uint::bytes) {
result.push_char(sep);
result.push_str(format!("{:02x}", v & 0xFF));
v >>= 8;
sep = '-';
}
}
result.push_char(']');
return result;
}
fn copy_bits(in_vec: &[uint], out_vec: &mut [uint]) -> bool {
bitwise(out_vec, in_vec, |_, b| b)
}
fn join_bits<O:DataFlowOperator>(oper: &O,
in_vec: &[uint],
out_vec: &mut [uint]) -> bool {
bitwise(out_vec, in_vec, |a, b| oper.join(a, b))
}
#[inline]
fn bitwise(out_vec: &mut [uint], in_vec: &[uint], op: |uint, uint| -> uint)
-> bool {
assert_eq!(out_vec.len(), in_vec.len());
let mut changed = false;
for (out_elt, in_elt) in out_vec.mut_iter().zip(in_vec.iter()) {
let old_val = *out_elt;
let new_val = op(old_val, *in_elt);
*out_elt = new_val;
changed |= (old_val != new_val);
}
changed
}
fn set_bit(words: &mut [uint], bit: uint) -> bool {
debug!("set_bit: words={} bit={}",
mut_bits_to_str(words), bit_str(bit));
let word = bit / uint::bits;
let bit_in_word = bit % uint::bits;
let bit_mask = 1 << bit_in_word;
debug!("word={} bit_in_word={} bit_mask={}", word, bit_in_word, word);
let oldv = words[word];
let newv = oldv | bit_mask;
words[word] = newv;
oldv != newv
}
fn bit_str(bit: uint) -> ~str {
let byte = bit >> 8;
let lobits = 1 << (bit & 0xFF);
format!("[{}:{}-{:02x}]", bit, byte, lobits)
}
fn reslice<'a>(v: &'a mut [uint]) -> &'a [uint] {
// bFIXME(#5074) this function should not be necessary at all
unsafe {
cast::transmute(v)
}
}