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Reverse #13034 

It has been found that #13034 was flawed and caused regression #13867.
This patch reveres the changes made by it except the companion tests.
This commit is contained in:
Edward Wang 2014-05-04 22:08:45 +08:00
parent 8895f25241
commit 7adc48527f
1 changed files with 8 additions and 66 deletions
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74
src/librustc/middle/trans/_match.rs
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@ -289,42 +289,6 @@ fn opt_eq(tcx: &ty::ctxt, a: &Opt, b: &Opt) -> bool {
}
}
fn opt_overlap(tcx: &ty::ctxt, a: &Opt, b: &Opt) -> bool {
match (a, b) {
(&lit(a), &lit(b)) => {
let a_expr = lit_to_expr(tcx, &a);
let b_expr = lit_to_expr(tcx, &b);
match const_eval::compare_lit_exprs(tcx, a_expr, b_expr) {
Some(val1) => val1 == 0,
None => fail!("opt_overlap: type mismatch"),
}
}
(&range(a1, a2), &range(b1, b2)) => {
let m1 = const_eval::compare_lit_exprs(tcx, a1, b2);
let m2 = const_eval::compare_lit_exprs(tcx, b1, a2);
match (m1, m2) {
// two ranges [a1, a2] and [b1, b2] overlap iff:
// a1 <= b2 && b1 <= a2
(Some(val1), Some(val2)) => (val1 <= 0 && val2 <= 0),
_ => fail!("opt_overlap: type mismatch"),
}
}
(&range(a1, a2), &lit(b)) | (&lit(b), &range(a1, a2)) => {
let b_expr = lit_to_expr(tcx, &b);
let m1 = const_eval::compare_lit_exprs(tcx, a1, b_expr);
let m2 = const_eval::compare_lit_exprs(tcx, a2, b_expr);
match (m1, m2) {
// b is in range [a1, a2] iff a1 <= b and b <= a2
(Some(val1), Some(val2)) => (val1 <= 0 && 0 <= val2),
_ => fail!("opt_overlap: type mismatch"),
}
}
_ => fail!("opt_overlap: expect lit or range")
}
}
pub enum opt_result<'a> {
single_result(Result<'a>),
lower_bound(Result<'a>),
@ -634,30 +598,16 @@ fn enter_opt<'a, 'b>(
let tcx = bcx.tcx();
let dummy = @ast::Pat {id: 0, node: ast::PatWild, span: DUMMY_SP};
let mut i = 0;
// By the virtue of fact that we are in `trans` already, `enter_opt` is able
// to prune sub-match tree aggressively based on exact equality. But when it
// comes to literal or range, that strategy may lead to wrong result if there
// are guard function or multiple patterns inside tuple; in that case, pruning
// based on the overlap of patterns is required.
//
// Ideally, when constructing the sub-match tree for certain arm, only those
// arms beneath it matter. But that isn't how algorithm works right now and
// all other arms are taken into consideration when computing `guarded` below.
// That is ok since each round of `compile_submatch` guarantees to trim one
// "column" of arm patterns and the algorithm will converge.
let guarded = m.iter().any(|x| x.data.arm.guard.is_some());
let multi_pats = m.len() > 0 && m[0].pats.len() > 1;
enter_match(bcx, &tcx.def_map, m, col, val, |p| {
let answer = match p.node {
ast::PatEnum(..) |
ast::PatIdent(_, _, None) if pat_is_const(&tcx.def_map, p) => {
let const_def = tcx.def_map.borrow().get_copy(&p.id);
let const_def_id = ast_util::def_id_of_def(const_def);
let konst = lit(ConstLit(const_def_id));
match guarded || multi_pats {
false if opt_eq(tcx, &konst, opt) => Some(Vec::new()),
true if opt_overlap(tcx, &konst, opt) => Some(Vec::new()),
_ => None,
if opt_eq(tcx, &lit(ConstLit(const_def_id)), opt) {
Some(Vec::new())
} else {
None
}
}
ast::PatEnum(_, ref subpats) => {
@ -682,20 +632,12 @@ fn enter_opt<'a, 'b>(
}
}
ast::PatLit(l) => {
let lit_expr = lit(ExprLit(l));
match guarded || multi_pats {
false if opt_eq(tcx, &lit_expr, opt) => Some(Vec::new()),
true if opt_overlap(tcx, &lit_expr, opt) => Some(Vec::new()),
_ => None,
}
if opt_eq(tcx, &lit(ExprLit(l)), opt) { Some(Vec::new()) }
else { None }
}
ast::PatRange(l1, l2) => {
let rng = range(l1, l2);
match guarded || multi_pats {
false if opt_eq(tcx, &rng, opt) => Some(Vec::new()),
true if opt_overlap(tcx, &rng, opt) => Some(Vec::new()),
_ => None,
}
if opt_eq(tcx, &range(l1, l2), opt) { Some(Vec::new()) }
else { None }
}
ast::PatStruct(_, ref field_pats, _) => {
if opt_eq(tcx, &variant_opt(bcx, p.id), opt) {