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rustc: Skip null when translating string concatenation

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This commit is contained in:
Patrick Walton 2011-07-18 18:00:45 -07:00
parent 08eabde97b
commit 07a68df3b7
2 changed files with 6 additions and 1 deletions
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6
src/comp/middle/trans_vec.rs
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@ -127,8 +127,10 @@ fn trans_concat(&@block_ctxt cx, &dest in_dest, &span sp, ty::t t,
// TODO: Detect "a + [ literal ]" and optimize to copying the literal
// elements in directly.
// Translate the LHS and RHS. Pull out their length and data.
auto t = ty::expr_ty(bcx_tcx(bcx), lhs);
auto skip_null = ty::type_is_str(bcx_tcx(bcx), t);
// Translate the LHS and RHS. Pull out their length and data.
auto lhs_tmp = trans_dps::dest_alias(bcx_tcx(bcx), t);
bcx = trans_dps::trans_expr(bcx, lhs_tmp, lhs);
auto lllhsptr = trans_dps::dest_ptr(lhs_tmp);
@ -142,6 +144,8 @@ fn trans_concat(&@block_ctxt cx, &dest in_dest, &span sp, ty::t t,
r0 = get_len_and_data(bcx, t, llrhsptr);
bcx = r0._0; auto llrhslen = r0._1; auto llrhsdata = r0._2;
if skip_null { lllhslen = bcx.build.Sub(lllhslen, C_int(1)); }
// Allocate the destination.
auto r1 = trans_dps::spill_alias(bcx, in_dest, t);
bcx = r1._0; auto dest = r1._1;

1
src/comp/middle/ty.rs
View file

@ -915,6 +915,7 @@ fn type_is_sequence(&ctxt cx, &t ty) -> bool {
fn type_is_str(&ctxt cx, &t ty) -> bool {
alt (struct(cx, ty)) {
case (ty_str) { ret true; }
case (ty_istr) { ret true; }
case (_) { ret false; }
}
}