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Optimize vec::from_elem with manual inlining (borrowck 1.85x speedup on libstd)

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Corey Richardson
2013-06-01 00:55:19 -04:00
parent e516d2333f
commit c299230f3d
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| { do as_mut_buf(v) |p, _len| {
let mut i: uint = 0u; let mut i: uint = 0u;
while i < n_elts { while i < n_elts {
intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), op(i));
op(i));
i += 1u; i += 1u;
} }
} }
@@ -166,7 +165,20 @@ pub fn from_fn<T>(n_elts: uint, op: old_iter::InitOp<T>) -> ~[T] {
* to the value `t`. * to the value `t`.
*/ */
pub fn from_elem<T:Copy>(n_elts: uint, t: T) -> ~[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 /// Creates a new unique vector with the same contents as the slice