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auto merge of #6876 : cmr/rust/from_elem_opts, r=Aatch

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borrowck 1.85x speedup on libstd
This commit is contained in:
bors 2013-05-31 22:04:38 -07:00
commit c23843c447
1 changed files with 15 additions and 3 deletions
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18
src/libstd/vec.rs
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@ -149,8 +149,7 @@ pub fn from_fn<T>(n_elts: uint, op: old_iter::InitOp<T>) -> ~[T] {
do as_mut_buf(v) |p, _len| {
let mut i: uint = 0u;
while i < n_elts {
intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)),
op(i));
intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), op(i));
i += 1u;
}
}
@ -166,7 +165,20 @@ pub fn from_fn<T>(n_elts: uint, op: old_iter::InitOp<T>) -> ~[T] {
* to the value `t`.
*/
pub fn from_elem<T:Copy>(n_elts: uint, t: T) -> ~[T] {
from_fn(n_elts, |_i| copy t)
// hack: manually inline from_fn for 2x plus speedup (sadly very important, from_elem is a
// bottleneck in borrowck!)
unsafe {
let mut v = with_capacity(n_elts);
do as_mut_buf(v) |p, _len| {
let mut i = 0u;
while i < n_elts {
intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), copy t);
i += 1u;
}
}
raw::set_len(&mut v, n_elts);
v
}
}
/// Creates a new unique vector with the same contents as the slice