Replace uses of __libcpp_ctz by __countr_zero
#132639
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@llvm/pr-subscribers-libcxx Author: None (PaulXiCao) ChangesCloses #131179. Full diff: https://github.com/llvm/llvm-project/pull/132639.diff 3 Files Affected:
diff --git a/libcxx/include/__algorithm/sort.h b/libcxx/include/__algorithm/sort.h
index 8dd0721f2c65f..015d6531b1d87 100644
--- a/libcxx/include/__algorithm/sort.h
+++ b/libcxx/include/__algorithm/sort.h
@@ -359,9 +359,9 @@ inline _LIBCPP_HIDE_FROM_ABI void __swap_bitmap_pos(
// Swap one pair on each iteration as long as both bitsets have at least one
// element for swapping.
while (__left_bitset != 0 && __right_bitset != 0) {
- difference_type __tz_left = __libcpp_ctz(__left_bitset);
+ difference_type __tz_left = __countr_zero(__left_bitset);
__left_bitset = __libcpp_blsr(__left_bitset);
- difference_type __tz_right = __libcpp_ctz(__right_bitset);
+ difference_type __tz_right = __countr_zero(__right_bitset);
__right_bitset = __libcpp_blsr(__right_bitset);
_Ops::iter_swap(__first + __tz_left, __last - __tz_right);
}
diff --git a/libcxx/include/__cxx03/__algorithm/find.h b/libcxx/include/__cxx03/__algorithm/find.h
index ff5ac9b8b1bd0..29486e9438711 100644
--- a/libcxx/include/__cxx03/__algorithm/find.h
+++ b/libcxx/include/__cxx03/__algorithm/find.h
@@ -108,7 +108,7 @@ __find_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
__storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
__storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
if (__b)
- return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
+ return _It(__first.__seg_, static_cast<unsigned>(std::__countr_zero(__b)));
if (__n == __dn)
return __first + __n;
__n -= __dn;
@@ -118,14 +118,14 @@ __find_bool(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word) {
__storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_);
if (__b)
- return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
+ return _It(__first.__seg_, static_cast<unsigned>(std::__countr_zero(__b)));
}
// do last partial word
if (__n > 0) {
__storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
__storage_type __b = std::__invert_if<!_ToFind>(*__first.__seg_) & __m;
if (__b)
- return _It(__first.__seg_, static_cast<unsigned>(std::__libcpp_ctz(__b)));
+ return _It(__first.__seg_, static_cast<unsigned>(std::__countr_zero(__b)));
}
return _It(__first.__seg_, static_cast<unsigned>(__n));
}
diff --git a/libcxx/include/__cxx03/__algorithm/sort.h b/libcxx/include/__cxx03/__algorithm/sort.h
index 009ebf717bbd8..47472afbbe562 100644
--- a/libcxx/include/__cxx03/__algorithm/sort.h
+++ b/libcxx/include/__cxx03/__algorithm/sort.h
@@ -399,9 +399,9 @@ inline _LIBCPP_HIDE_FROM_ABI void __swap_bitmap_pos(
// Swap one pair on each iteration as long as both bitsets have at least one
// element for swapping.
while (__left_bitset != 0 && __right_bitset != 0) {
- difference_type __tz_left = __libcpp_ctz(__left_bitset);
+ difference_type __tz_left = __countr_zero(__left_bitset);
__left_bitset = __libcpp_blsr(__left_bitset);
- difference_type __tz_right = __libcpp_ctz(__right_bitset);
+ difference_type __tz_right = __countr_zero(__right_bitset);
__right_bitset = __libcpp_blsr(__right_bitset);
_Ops::iter_swap(__first + __tz_left, __last - __tz_right);
}
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Hi @PaulXiCao, thanks for your efforts in addressing this issue! Just to provide some context—this issue was opened a week ago as a follow-up to my previous work and was assigned to me shortly thereafter. I’ve been actively working on related patches, but since this change depends on dropping Clang 18 support, I hadn’t submitted a patch yet. While I truly appreciate your enthusiasm and contribution, I think it would be helpful in the future to check with the assignee before working on a recently assigned issue, especially if it’s a follow-up to their prior work. This can help avoid duplicated effort and ensure smoother collaboration. Thanks again! |
FYI @winner245 removing Clang-18 support is blocked by some CI runners, the maintainers for these runners are working on upgrading the clang version of their runners. |
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Hi @mordante, thank you for the update on the current status of removing Clang 18 support, which is currently blocked by some CI runners. I understand that the changes in this patch will need to be put on hold until Clang 18 support is officially dropped (@PaulXiCao). |
Looking at the status of the CI this works in Clang-18; the ARM runners are still on Clang-18. |
The primary goal of #131179 (based on my discussion with @ldionne in #122641 (comment) ) was to eliminate all usages of That being said, the current patch doesn't fully address issue #131179. Most of the changes are applied to frozen header files, which I believe should stay unchanged unless there is a strong reason. That's why I didn't make these changes in my earlier patch. |
I didn't look into the patch or which Clang version supports the built-in. If you say that's Clang-19 this patch indeed needs to be post-poned until we can drop Clang-18 support. I mainly wanted to update you on the status of Clang-18 support. |
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Closing per @winner245 's comment -- we already have a patch ready to go once Clang 18 is dropped, and this patch as-is doesn't implement all that we wanted from #131179. |
Closes #131179.