[libcxx-commits] [libcxx] [libc++] Optimize num_get integral functions (PR #121795)

[Louis Dionne via libcxx-commits]

================
@@ -836,98 +796,137 @@ _InputIterator num_get<_CharT, _InputIterator>::__do_get_signed(
   char_type __atoms1[__atoms_size];
   const char_type* __atoms = this->__do_widen(__iob, __atoms1);
   string __grouping        = this->__stage2_int_prep(__iob, __thousands_sep);
-  string __buf;
-  __buf.resize(__buf.capacity());
-  char* __a     = &__buf[0];
-  char* __a_end = __a;
   unsigned __g[__num_get_base::__num_get_buf_sz];
   unsigned* __g_end = __g;
   unsigned __dc     = 0;
-  for (; __b != __e; ++__b) {
-    if (__a_end == __a + __buf.size()) {
-      size_t __tmp = __buf.size();
-      __buf.resize(2 * __buf.size());
-      __buf.resize(__buf.capacity());
-      __a     = &__buf[0];
-      __a_end = __a + __tmp;
+
+  if (__first == __last) {
+    __err |= ios_base::eofbit;
+    return __first;
+  }
+
+  while (!__grouping.empty() && *__first == __thousands_sep) {
+    ++__first;
+    if (__g_end - __g < this->__num_get_buf_sz) {
+      *__g_end++ = __dc;
+      __dc       = 0;
     }
-    if (this->__stage2_int_loop(
-            *__b,
-            __base,
-            __a,
-            __a_end,
-            __dc,
-            __thousands_sep,
-            __grouping,
-            __g,
-            __g_end,
-            const_cast<char_type*>(__atoms)))
-      break;
   }
-  if (__grouping.size() != 0 && __g_end - __g < __num_get_base::__num_get_buf_sz)
-    *__g_end++ = __dc;
-  // Stage 3
-  __v = std::__num_get_signed_integral<_Signed>(__a, __a_end, __err, __base);
-  // Digit grouping checked
-  __check_grouping(__grouping, __g, __g_end, __err);
----------------
ldionne wrote:

Can you double-check whether this one is still used?

https://github.com/llvm/llvm-project/pull/121795