diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 7b78e148fbd38f998214835c9e71b874df10bd7c..94897a654c9506f554466f54bdb86a7981f123be 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/config.h.in b/libstdc++-v3/config.h.in
index 197e8e691cb694571990c886cddd65997df86cfb..e545488386a967188d931d28a4423bf616b2e602 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -929,9 +929,6 @@
 /* Define if get_nprocs is available in <sys/sysinfo.h>. */
 #undef _GLIBCXX_USE_GET_NPROCS
 
-/* Define if __int128 is supported on this host. */
-#undef _GLIBCXX_USE_INT128
-
 /* Define if LFS support is available. */
 #undef _GLIBCXX_USE_LFS
 
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 272bd993a9caf71ef345fdc263bc77621891274c..067b5d1ae8ebf6474409fd964b2ef59f874c7a4f 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -16218,7 +16218,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
   # Fake what AC_TRY_COMPILE does, without linking as this is
   # unnecessary for this test.
 
-    cat > conftest.$ac_ext << EOF
+  cat > conftest.$ac_ext << EOF
 #line 16222 "configure"
 template<typename T1, typename T2>
   struct same
@@ -16227,40 +16227,6 @@ template<typename T1, typename T2>
 template<typename T>
   struct same<T, T>;
 
-int main()
-{
-  typename same<long, __int128>::type                i1;
-  typename same<long long, __int128>::type           i2;
-}
-EOF
-
-    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __int128" >&5
-$as_echo_n "checking for __int128... " >&6; }
-    if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_compile\""; } >&5
-  (eval $ac_compile) 2>&5
-  ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; then
-
-$as_echo "#define _GLIBCXX_USE_INT128 1" >>confdefs.h
-
-      enable_int128=yes
-    else
-      enable_int128=no
-    fi
-    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_int128" >&5
-$as_echo "$enable_int128" >&6; }
-    rm -f conftest*
-
-    cat > conftest.$ac_ext << EOF
-#line 16256 "configure"
-template<typename T1, typename T2>
-  struct same
-  { typedef T2 type; };
-
-template<typename T>
-  struct same<T, T>;
-
 int main()
 {
   typename same<double, __float128>::type      f1;
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 95dd9ce5da5fe040bd24dce09a0a7f5bb2cd79f3..a816ff79d16b49f753f2103ebaf40e79e92bd512 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 1b9cc5f16a9aa3db97767e08024acf6b54a68f78..0da013c5f457f1802eae39a5ee728d6f02be9cab 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 6e407f31e30b0e4f5a4affb602c2f3b6ecebfd44..193702e677a6af0c857e79a4a620d01227f4c1c2 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
 	>;