commit 93826d102b08878f08523912a1576f930dd00989
author Nikolas Klauser <nikolasklauser@berlin.de> Tue Jan 04 17:24:03 2022 +0100
committer Copybara-Service <copybara-worker@google.com> Tue Jan 11 14:27:14 2022 -0800
tree 604dfd71c302beecdc600c944d9027149fe3098a
parent 6e9d269f267a4e6946a2dc42058f2f20cea2be81

[libc++] Introduce __fits_in_sso()

Introduce `__fits_in_sso()` to put the constexpr tests into a central place.

Reviewed By: ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D116487

NOKEYCHECK=True
GitOrigin-RevId: fcfc0e7ad34c48e0c3a36516b5098ba465b66d69

include/string

diff --git a/include/string b/include/string
index 04d3e41..c4f2b00 100644
--- a/include/string
+++ b/include/string
@@ -1466,6 +1466,11 @@
 #endif // _LIBCPP_DEBUG_LEVEL == 2
 
 private:
+    _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI static bool __fits_in_sso(size_type __sz) {
+        // SSO is disabled during constant evaluation because `__is_long` isn't constexpr friendly
+        return !__libcpp_is_constant_evaluated() && (__sz < __min_cap);
+    }
+
     _LIBCPP_INLINE_VISIBILITY
     allocator_type& __alloc() _NOEXCEPT
         {return __r_.second();}
@@ -1864,7 +1869,7 @@
     if (__reserve > max_size())
         this->__throw_length_error();
     pointer __p;
-    if (__reserve < __min_cap)
+    if (__fits_in_sso(__reserve))
     {
         __set_short_size(__sz);
         __p = __get_short_pointer();
@@ -1888,7 +1893,7 @@
     if (__sz > max_size())
         this->__throw_length_error();
     pointer __p;
-    if (__sz < __min_cap)
+    if (__fits_in_sso(__sz))
     {
         __set_short_size(__sz);
         __p = __get_short_pointer();
@@ -1964,7 +1969,7 @@
 void basic_string<_CharT, _Traits, _Allocator>::__init_copy_ctor_external(
     const value_type* __s, size_type __sz) {
   pointer __p;
-  if (__sz < __min_cap) {
+  if (__fits_in_sso(__sz)) {
     __p = __get_short_pointer();
     __set_short_size(__sz);
   } else {
@@ -2027,7 +2032,7 @@
     if (__n > max_size())
         this->__throw_length_error();
     pointer __p;
-    if (__n < __min_cap)
+    if (__fits_in_sso(__n))
     {
         __set_short_size(__n);
         __p = __get_short_pointer();
@@ -2158,7 +2163,7 @@
     if (__sz > max_size())
         this->__throw_length_error();
     pointer __p;
-    if (__sz < __min_cap)
+    if (__fits_in_sso(__sz))
     {
         __set_short_size(__sz);
         __p = __get_short_pointer();
@@ -2350,7 +2355,7 @@
 basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s, size_type __n)
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::assign received nullptr");
-    return (__builtin_constant_p(__n) && __n < __min_cap)
+    return (__builtin_constant_p(__n) && __fits_in_sso(__n))
                ? __assign_short(__s, __n)
                : __assign_external(__s, __n);
 }
@@ -2553,7 +2558,7 @@
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::assign received nullptr");
     return __builtin_constant_p(*__s)
-               ? (traits_type::length(__s) < __min_cap
+               ? (__fits_in_sso(traits_type::length(__s))
                       ? __assign_short(__s, traits_type::length(__s))
                       : __assign_external(__s, traits_type::length(__s)))
                : __assign_external(__s);