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auto merge of #6876 : cmr/rust/from_elem_opts, r=Aatch
borrowck 1.85x speedup on libstd
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commit
c23843c447
@ -149,8 +149,7 @@ pub fn from_fn<T>(n_elts: uint, op: old_iter::InitOp<T>) -> ~[T] {
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do as_mut_buf(v) |p, _len| {
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let mut i: uint = 0u;
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while i < n_elts {
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intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)),
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op(i));
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intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), op(i));
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i += 1u;
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}
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}
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@ -166,7 +165,20 @@ pub fn from_fn<T>(n_elts: uint, op: old_iter::InitOp<T>) -> ~[T] {
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* to the value `t`.
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*/
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pub fn from_elem<T:Copy>(n_elts: uint, t: T) -> ~[T] {
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from_fn(n_elts, |_i| copy t)
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// hack: manually inline from_fn for 2x plus speedup (sadly very important, from_elem is a
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// bottleneck in borrowck!)
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unsafe {
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let mut v = with_capacity(n_elts);
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do as_mut_buf(v) |p, _len| {
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let mut i = 0u;
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while i < n_elts {
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intrinsics::move_val_init(&mut(*ptr::mut_offset(p, i)), copy t);
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i += 1u;
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}
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}
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raw::set_len(&mut v, n_elts);
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v
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}
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}
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/// Creates a new unique vector with the same contents as the slice
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