================
@@ -192,9 +204,11 @@ class ASTVector {
this->grow(C, this->size()+NumInputs);
// Copy the new elements over.
- // TODO: NEED To compile time dispatch on whether in_iter is a random
access
- // iterator to use the fast uninitialized_copy.
----------------
snarang181 wrote:
@zwuis,thanks for your review.
std::distance and std::uninitialized_copy both rely on iterator tag dispatch,
which determines the implementation at overload resolution time rather than
through explicit compile-time branching. While std::distance will use an O(1)
path for random access iterators, that dispatch happens inside the library and
isn’t guaranteed to inline cleanly into templated call sites like append().
Moreover, std::uninitialized_copy always performs an element-by-element loop
regardless of iterator category, offering no benefit when the range size
(NumInputs) is already known. Using std::uninitialized_copy_n with a
precomputed element count avoids the per-iteration sentinel checks and enables
the compiler to generate tighter loops.
https://github.com/llvm/llvm-project/pull/162000
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