[libcxx-commits] [libcxx] [libc++] Optimize `to_chars` for bases 2, 8 and 16 (PR #223222)

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git-clang-format --diff origin/main HEAD --extensions h -- libcxx/include/__charconv/to_chars_integral.h --diff_from_common_commit
``````````

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``````````diff
diff --git a/libcxx/include/__charconv/to_chars_integral.h b/libcxx/include/__charconv/to_chars_integral.h
index 3fbbd6a8f..104319abe 100644
--- a/libcxx/include/__charconv/to_chars_integral.h
+++ b/libcxx/include/__charconv/to_chars_integral.h
@@ -140,7 +140,7 @@ struct _LIBCPP_HIDDEN __integral<2> {
     constexpr auto __c0_offset_mask = uint64_t{0x3030'3030'3030'3030};
     while (__value >= __divisor) {
       const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-      auto __cs            = __digits | __c0_offset_mask;
+      auto __cs           = __digits | __c0_offset_mask;
 #ifdef _LIBCPP_LITTLE_ENDIAN
       __cs = __builtin_bswap64(__cs);
 #endif
@@ -150,11 +150,11 @@ struct _LIBCPP_HIDDEN __integral<2> {
       __builtin_memcpy(__p, __chars.__data, __ncs_per_word);
     }
     const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-    auto __cs            = __digits | __c0_offset_mask;
+    auto __cs           = __digits | __c0_offset_mask;
 #ifdef _LIBCPP_LITTLE_ENDIAN
     __cs = __builtin_bswap64(__cs);
 #endif
-    const auto __chars = __builtin_bit_cast(__chars_storage<__ncs_per_word>, __cs);
+    const auto __chars     = __builtin_bit_cast(__chars_storage<__ncs_per_word>, __cs);
     const auto __remaining = static_cast<size_t>(__p - __first);
     __builtin_memcpy(__first, __chars.__data + __ncs_per_word - __remaining, __remaining);
     return {__last, errc(0)};
@@ -177,8 +177,8 @@ struct _LIBCPP_HIDDEN __integral<8> {
     int __n         = __width(__value);
     if (__n > __cap)
       return {__last, errc::value_too_large};
-    __last                   = __first + __n;
-    char* __p                = __last;
+    __last    = __first + __n;
+    char* __p = __last;
 
     constexpr auto __ncs_per_word   = 8u;
     constexpr auto __divisor        = 1u << (3 * __ncs_per_word);
@@ -186,7 +186,7 @@ struct _LIBCPP_HIDDEN __integral<8> {
     constexpr auto __c0_offset_mask = uint64_t{0x3030'3030'3030'3030};
     while (__value >= __divisor) {
       const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-      auto __cs            = __digits | __c0_offset_mask;
+      auto __cs           = __digits | __c0_offset_mask;
 #ifdef _LIBCPP_LITTLE_ENDIAN
       __cs = __builtin_bswap64(__cs);
 #endif
@@ -196,11 +196,11 @@ struct _LIBCPP_HIDDEN __integral<8> {
       __builtin_memcpy(__p, __chars.__data, __ncs_per_word);
     }
     const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-    auto __cs            = __digits | __c0_offset_mask;
+    auto __cs           = __digits | __c0_offset_mask;
 #ifdef _LIBCPP_LITTLE_ENDIAN
     __cs = __builtin_bswap64(__cs);
 #endif
-    const auto __chars = __builtin_bit_cast(__chars_storage<__ncs_per_word>, __cs);
+    const auto __chars     = __builtin_bit_cast(__chars_storage<__ncs_per_word>, __cs);
     const auto __remaining = static_cast<size_t>(__p - __first);
     __builtin_memcpy(__first, __chars.__data + __ncs_per_word - __remaining, __remaining);
     return {__last, errc(0)};
@@ -235,8 +235,8 @@ struct _LIBCPP_HIDDEN __integral<16> {
     constexpr auto __c0_offset_mask = uint64_t{0x3030'3030'3030'3030};
     while (__value >= __divisor) {
       const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-    const auto __alpha = ((__digits + __add_six_mask) & __high_bit_mask) >> 4;
-    auto __cs          = __digits + __c0_offset_mask + __alpha * 0x27;
+      const auto __alpha  = ((__digits + __add_six_mask) & __high_bit_mask) >> 4;
+      auto __cs           = __digits + __c0_offset_mask + __alpha * 0x27;
 #ifdef _LIBCPP_LITTLE_ENDIAN
       __cs = __builtin_bswap64(__cs);
 #endif
@@ -246,8 +246,8 @@ struct _LIBCPP_HIDDEN __integral<16> {
       __builtin_memcpy(__p, __chars.__data, __ncs_per_word);
     }
     const auto __digits = __builtin_elementwise_pdep(static_cast<uint64_t>(__value), __dep_mask);
-    const auto __alpha = ((__digits + __add_six_mask) & __high_bit_mask) >> 4;
-    auto __cs          = __digits + __c0_offset_mask + __alpha * 0x27;
+    const auto __alpha  = ((__digits + __add_six_mask) & __high_bit_mask) >> 4;
+    auto __cs           = __digits + __c0_offset_mask + __alpha * 0x27;
 #ifdef _LIBCPP_LITTLE_ENDIAN
     __cs = __builtin_bswap64(__cs);
 #endif

``````````

</details>


https://github.com/llvm/llvm-project/pull/223222