From 486293084523302ecec255f0ef132fd3e333d0ab Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Sun, 9 May 2021 08:30:15 -0700
Subject: [PATCH] Optimize format string compilation

---
 include/fmt/compile.h |  9 +++++----
 include/fmt/format.h  | 27 +++++++++++++++++++++++----
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/include/fmt/compile.h b/include/fmt/compile.h
index 7ff2fe86..9c0ff9bd 100644
--- a/include/fmt/compile.h
+++ b/include/fmt/compile.h
@@ -319,7 +319,8 @@ template <typename Char, typename T, int N> struct spec_field {
   formatter<T, Char> fmt;
 
   template <typename OutputIt, typename... Args>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  constexpr FMT_INLINE OutputIt format(OutputIt out,
+                                       const Args&... args) const {
     const auto& vargs =
         make_format_args<basic_format_context<OutputIt, Char>>(args...);
     basic_format_context<OutputIt, Char> ctx(out, vargs);
@@ -556,9 +557,9 @@ template <typename CompiledFormat, typename... Args,
           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
 FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
                                           const Args&... args) {
-  basic_memory_buffer<Char> buffer;
-  cf.format(detail::buffer_appender<Char>(buffer), args...);
-  return to_string(buffer);
+  auto s = std::basic_string<Char>();
+  cf.format(std::back_inserter(s), args...);
+  return s;
 }
 
 template <typename OutputIt, typename CompiledFormat, typename... Args,
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 58512bd5..089f042d 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1609,9 +1609,9 @@ FMT_CONSTEXPR inline void prefix_append(unsigned& prefix, unsigned value) {
 template <typename Char, typename OutputIt, typename T,
           FMT_ENABLE_IF(std::is_integral<T>::value &&
                         !std::is_same<T, bool>::value)>
-FMT_CONSTEXPR OutputIt write(OutputIt out, T value,
-                             const basic_format_specs<Char>& specs,
-                             locale_ref loc) {
+FMT_CONSTEXPR FMT_INLINE OutputIt
+write_int(OutputIt out, T value, const basic_format_specs<Char>& specs,
+          locale_ref loc) {
   auto prefix = 0u;
   auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
   if (is_negative(value)) {
@@ -1673,6 +1673,25 @@ FMT_CONSTEXPR OutputIt write(OutputIt out, T value,
   }
   return out;
 }
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        std::is_same<OutputIt, buffer_appender<Char>>::value)>
+FMT_CONSTEXPR OutputIt write(OutputIt out, T value,
+                             const basic_format_specs<Char>& specs,
+                             locale_ref loc) {
+  return write_int(out, value, specs, loc);
+}
+// An inlined version of format_int used in format string compilation.
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<OutputIt, buffer_appender<Char>>::value)>
+FMT_CONSTEXPR FMT_INLINE OutputIt write(OutputIt out, T value,
+                                        const basic_format_specs<Char>& specs,
+                                        locale_ref loc) {
+  return write_int(out, value, specs, loc);
+}
 
 template <typename OutputIt, typename StrChar, typename Char>
 FMT_CONSTEXPR OutputIt write(OutputIt out, basic_string_view<StrChar> s,
@@ -2900,7 +2919,7 @@ struct formatter<T, Char,
   }
 
   template <typename FormatContext>
-  FMT_CONSTEXPR auto format(const T& val, FormatContext& ctx) const
+  FMT_CONSTEXPR FMT_INLINE auto format(const T& val, FormatContext& ctx) const
       -> decltype(ctx.out()) {
     if (specs_.width_ref.kind != detail::arg_id_kind::none ||
         specs_.precision_ref.kind != detail::arg_id_kind::none) {