diff --git a/gcc/config.in b/gcc/config.in
index 1796e1d..11ebf5c 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1846,6 +1846,13 @@
 #endif
 
 
+/* Define this macro if C++ __builtin_constant_p with constexpr does not crash
+   with a variable. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_WORKING_CXX_BUILTIN_CONSTANT_P
+#endif
+
+
 /* Define to 1 if `fork' works. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_WORKING_FORK
@@ -1865,7 +1872,8 @@
 #endif
 
 
-/* Define if your assembler supports .dwsect 0xB0000 */
+/* Define if your assembler supports AIX debug frame section label reference.
+   */
 #ifndef USED_FOR_TARGET
 #undef HAVE_XCOFF_DWARF_EXTRAS
 #endif
diff --git a/gcc/configure b/gcc/configure
index ff646e8..2798231 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -6534,6 +6534,43 @@ fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 
+# Check if C++ __builtin_constant_p works properly.  Without the fix
+# for PR 65656, g++ miscompiles __builtin_constant_p in wi::lrshift in
+# wide-int.h.  Add a check with PR 65656 testcase to verify that C++
+# __builtin_constant_p works properly.
+if test "$GCC" = yes; then
+  saved_CFLAGS="$CFLAGS"
+  saved_CXXFLAGS="$CXXFLAGS"
+  CFLAGS="$CFLAGS -O -x c++ -std=c++11"
+  CXXFLAGS="$CXXFLAGS -O -x c++ -std=c++11"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX __builtin_constant_p works with constexpr" >&5
+$as_echo_n "checking whether $CXX __builtin_constant_p works with constexpr... " >&6; }
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+foo (int argc)
+{
+  constexpr bool x = __builtin_constant_p(argc);
+  return x ? 1 : 0;
+}
+
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+$as_echo "#define HAVE_WORKING_CXX_BUILTIN_CONSTANT_P 1" >>confdefs.h
+
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  CFLAGS="$saved_CFLAGS"
+  CXXFLAGS="$saved_CXXFLAGS"
+fi
+
 # Check whether compiler is affected by placement new aliasing bug (PR 29286).
 # If the host compiler is affected by the bug, and we build with optimization
 # enabled (which happens e.g. when cross-compiling), the pool allocator may
@@ -18419,7 +18456,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18422 "configure"
+#line 18459 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -18525,7 +18562,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18528 "configure"
+#line 18565 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 4dc7c10..9791a96 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -416,6 +416,33 @@ struct X<long long> { typedef long long t; };
 ]], [[X<int64_t>::t x;]])],[],[AC_MSG_ERROR([error verifying int64_t uses long long])])
 fi
 
+# Check if C++ __builtin_constant_p works properly.  Without the fix
+# for PR 65656, g++ miscompiles __builtin_constant_p in wi::lrshift in
+# wide-int.h.  Add a check with PR 65656 testcase to verify that C++
+# __builtin_constant_p works properly.
+if test "$GCC" = yes; then
+  saved_CFLAGS="$CFLAGS"
+  saved_CXXFLAGS="$CXXFLAGS"
+  CFLAGS="$CFLAGS -O -x c++ -std=c++11"
+  CXXFLAGS="$CXXFLAGS -O -x c++ -std=c++11"
+  AC_MSG_CHECKING(whether $CXX __builtin_constant_p works with constexpr)
+  AC_COMPILE_IFELSE([
+int
+foo (int argc)
+{
+  constexpr bool x = __builtin_constant_p(argc);
+  return x ? 1 : 0;
+}
+],
+    [AC_MSG_RESULT([yes])
+     AC_DEFINE(HAVE_WORKING_CXX_BUILTIN_CONSTANT_P, 1,
+[Define this macro if C++ __builtin_constant_p with constexpr does not
+ crash with a variable.])],
+    [AC_MSG_RESULT([no])])
+  CFLAGS="$saved_CFLAGS"
+  CXXFLAGS="$saved_CXXFLAGS"
+fi
+
 # Check whether compiler is affected by placement new aliasing bug (PR 29286).
 # If the host compiler is affected by the bug, and we build with optimization
 # enabled (which happens e.g. when cross-compiling), the pool allocator may
diff --git a/gcc/system.h b/gcc/system.h
index ba2e963..e57787b 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -729,7 +729,7 @@ extern void fancy_abort (const char *, int, const char *) ATTRIBUTE_NORETURN;
 #define gcc_unreachable() (fancy_abort (__FILE__, __LINE__, __FUNCTION__))
 #endif
 
-#if GCC_VERSION >= 3001
+#if GCC_VERSION >= 3001 && defined HAVE_WORKING_CXX_BUILTIN_CONSTANT_P
 #define STATIC_CONSTANT_P(X) (__builtin_constant_p (X) && (X))
 #else
 #define STATIC_CONSTANT_P(X) (false && (X))
diff --git a/gcc/testsuite/gcc.dg/torture/pr69399.c b/gcc/testsuite/gcc.dg/torture/pr69399.c
new file mode 100644
index 0000000..3e17169
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr69399.c
@@ -0,0 +1,21 @@
+/* { dg-do run { target int128 } } */
+
+typedef __UINT64_TYPE__ u64;
+typedef unsigned __int128 u128;
+
+static unsigned __attribute__((noinline, noclone))
+foo(u64 u)
+{
+  u128 v = u | 0xffffff81;
+  v >>= 64;
+  return v;
+}
+
+int
+main()
+{
+  unsigned x = foo(27);
+  if (x != 0)
+    __builtin_abort();
+  return 0;
+}
