commit ad0a3be4df5eecc79075d899fd79179d0f61270e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue May 4 12:07:09 2021

    libstdc++: Remove _GLIBCXX_USE_INT128 autoconf macro
    
    We don't need to decide whether to use __int128 when running configure,
    we can do so at compilation time by seeing if __SIZEOF_INT128__ is
    defined and if it's greater than __SIZEOF_LONG_LONG__.
    
    This removes another unnecessary architecture-specific config macro in
    <bits/c++config.h>, so the same header can work for 32-bit or 64-bit
    compilation on AIX.
    
    libstdc++-v3/ChangeLog:
    
            * acinclude.m4 (GLIBCXX_ENABLE_INT128_FLOAT128): Remove
            checks for __int128 and rename to GLIBCXX_ENABLE_FLOAT128.
            * config.h.in: Regenerate.
            * configure: Regenerate.
            * configure.ac: Adjust to use GLIBCXX_ENABLE_FLOAT128.
            * include/bits/random.h (_Select_uint_least_t<s, 1>):
            Use __SIZEOF_INT128__ to decide whether to use __int128.
            * include/std/charconv (__to_chars_unsigned_type): Likewise.

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 7b78e148fbd..94897a654c9 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -3049,15 +3049,14 @@ EOF
 ])
 
 dnl
-dnl Check for GNU 128-bit integer and floating point types.
+dnl Check for GNU 128-bit floating point type.
 dnl
-dnl Note: also checks that the types aren't standard types.
+dnl Note: also checks that the type isn't a standard types.
 dnl
 dnl Defines:
-dnl  _GLIBCXX_USE_INT128
 dnl  ENABLE_FLOAT128
 dnl
-AC_DEFUN([GLIBCXX_ENABLE_INT128_FLOAT128], [
+AC_DEFUN([GLIBCXX_ENABLE_FLOAT128], [
 
   AC_LANG_SAVE
   AC_LANG_CPLUSPLUS
@@ -3065,34 +3064,7 @@ AC_DEFUN([GLIBCXX_ENABLE_INT128_FLOAT128], [
   # Fake what AC_TRY_COMPILE does, without linking as this is
   # unnecessary for this test.
 
-    cat > conftest.$ac_ext << EOF
-[#]line __oline__ "configure"
-template<typename T1, typename T2>
-  struct same
-  { typedef T2 type; };
-
-template<typename T>
-  struct same<T, T>;
-
-int main()
-{
-  typename same<long, __int128>::type                i1;
-  typename same<long long, __int128>::type           i2;
-}
-EOF
-
-    AC_MSG_CHECKING([for __int128])
-    if AC_TRY_EVAL(ac_compile); then
-      AC_DEFINE(_GLIBCXX_USE_INT128, 1,
-      [Define if __int128 is supported on this host.])
-      enable_int128=yes
-    else
-      enable_int128=no
-    fi
-    AC_MSG_RESULT($enable_int128)
-    rm -f conftest*
-
-    cat > conftest.$ac_ext << EOF
+  cat > conftest.$ac_ext << EOF
 [#]line __oline__ "configure"
 template<typename T1, typename T2>
   struct same
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 95dd9ce5da5..a816ff79d16 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -153,7 +153,7 @@ GLIBCXX_ENABLE_THREADS
 GLIBCXX_ENABLE_ATOMIC_BUILTINS
 GLIBCXX_ENABLE_LOCK_POLICY
 GLIBCXX_ENABLE_DECIMAL_FLOAT
-GLIBCXX_ENABLE_INT128_FLOAT128
+GLIBCXX_ENABLE_FLOAT128
 if test "$enable_float128" = yes; then
   port_specific_symbol_files="$port_specific_symbol_files \$(top_srcdir)/config/abi/pre/float128.ver"
 fi
diff --git a/libstdc++-v3/include/bits/random.h b/libstdc++-v3/include/bits/random.h
index 1b9cc5f16a9..0da013c5f45 100644
--- a/libstdc++-v3/include/bits/random.h
+++ b/libstdc++-v3/include/bits/random.h
@@ -99,7 +99,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       struct _Select_uint_least_t<__s, 2>
       { typedef unsigned long long type; };
 
-#ifdef _GLIBCXX_USE_INT128
+#if __SIZEOF_INT128__ > __SIZEOF_LONG_LONG__
     template<int __s>
       struct _Select_uint_least_t<__s, 1>
       { typedef unsigned __int128 type; };
diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index 6e407f31e30..193702e677a 100644
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -94,7 +94,7 @@ namespace __detail
     struct __to_chars_unsigned_type : __make_unsigned_selector_base
     {
       using _UInts = _List<unsigned int, unsigned long, unsigned long long
-#if _GLIBCXX_USE_INT128
+#if __SIZEOF_INT128__ > __SIZEOF_LONG_LONG__
 	, unsigned __int128
 #endif
 	>;