refactor: replace swizzle template recursion with C++17 constexpr - #1393
Open
DiamonDinoia wants to merge 2 commits into
Open
refactor: replace swizzle template recursion with C++17 constexpr #1393DiamonDinoia wants to merge 2 commits into
DiamonDinoia wants to merge 2 commits into
Conversation
…dicates The swizzle mask predicates were written as recursive class/function templates for the C++14 era. The project moved to C++17 in ea590d5, so they can be plain constexpr functions. is_identity, is_only_from_lo and is_only_from_hi become one-line fold expressions. is_dup_lo/is_dup_hi share a single is_dup_from_half loop -- a fold cannot express them because they compare v[i] against v[i+half]. Deletes get_at, identity_impl, dup_lo_impl, dup_hi_impl, only_from_lo_impl, only_from_hi_impl, get_nth_value, cross_impl, the forwarding wrappers, the unused is_cross_lane<uint32_t...> overload and the now-unused <cstdint>. Public signatures are unchanged, so no call site moves. Net -135/+28 lines. Verified equivalent to the previous implementation by 27230 static_assert(old(...) == new(...)) checks over 5446 masks (exhaustive for N=2 and N=4 including out-of-range indices, sampled plus structured patterns for N=8/N=16; uint32_t, uint16_t, int8_t, int64_t) under both g++ and clang++. The harness was mutation-tested: an off-by-one counter, a flipped comparison and a dropped range check are caught by 15, 370 and 1266 assertions respectively. Generated asm for ~45 swizzle kernels is byte-identical on sse2, avx2 and skylake-avx512. Adds static_asserts for narrow and signed index types (uint16_t, uint8_t, int8_t, int64_t) and for degenerate N=1/N=2 masks, which the previous tests only covered for uint32_t.
| XSIMD_INLINE constexpr bool is_dup_from_half() noexcept | ||
| { | ||
| constexpr std::size_t half = sizeof...(Vs) / 2; | ||
| constexpr T lo = Hi ? static_cast<T>(half) : T(0); |
Contributor
There was a problem hiding this comment.
i think this would be much easier to understand if implemented with the Hi == true logic speerated from the Hi == false logic.
{
if constexpr(Hi) { ...}
else { ...}
}
esp. for this condition if (v[i] < lo || v[i] >= hi || v[i + half] != v[i]) which looks different from i<H but V>=H) or (i>=H but V<H)
Address review: the shared is_dup_from_half<Hi> helper hid the intent behind 'v[i] < lo || v[i] >= hi || v[i + half] != v[i]'. Each direction is now a conjunction of named properties (in-range, only-from-half, equal-halves), differing by exactly one term. Adds the negative-index dup_lo case previously covered by the explicit lower bound.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
No description provided.