[libcxx-commits] [libcxx] 6eeabb9 - Speed up pre-C++20 operator<(std::tuple, std::tuple) (#214646)

[via libcxx-commits]

Author: higher-performance
Date: 2026-08-28T09:58:26-04:00
New Revision: 6eeabb90edaf78dc87aab3caf71eb8facf2b813e

URL: https://github.com/llvm/llvm-project/commit/6eeabb90edaf78dc87aab3caf71eb8facf2b813e
DIFF: https://github.com/llvm/llvm-project/commit/6eeabb90edaf78dc87aab3caf71eb8facf2b813e.diff

LOG: Speed up pre-C++20 operator<(std::tuple, std::tuple) (#214646)

Reduces the compile time of `operator<` for tuples, as `std::get` appears slow to compile.

Added: 
    

Modified: 
    libcxx/include/tuple

Removed: 
    


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diff  --git a/libcxx/include/tuple b/libcxx/include/tuple
index 67fd59b07c3e1..03ff3ef36ee1a 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -1192,9 +1192,11 @@ struct __tuple_less {
   template <class _Tp, class _Up>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool operator()(const _Tp& __x, const _Up& __y) {
     const size_t __idx = tuple_size<_Tp>::value - _Ip;
-    if (std::get<__idx>(__x) < std::get<__idx>(__y))
+    const auto& __a    = std::get<__idx>(__x);
+    const auto& __b    = std::get<__idx>(__y);
+    if (__a < __b)
       return true;
-    if (std::get<__idx>(__y) < std::get<__idx>(__x))
+    if (__b < __a)
       return false;
     return __tuple_less<_Ip - 1>()(__x, __y);
   }