1 files changed, 39 insertions, 2 deletions
diff --git a/gcc/configure b/gcc/configure
index ff646e8fcac..2798231bbd1 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