Add HAVE_WORKING_CXX_BUILTIN_CONSTANT_Phjl/pr69399/gcc-5-branch

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.

gcc/

	PR c++/69399
	* configure.ac: Check if C++ __builtin_constant_p works
	properly.
	(HAVE_WORKING_CXX_BUILTIN_CONSTANT_P): AC_DEFINE.
	* system.h (STATIC_CONSTANT_P): Use __builtin_constant_p only
	if HAVE_WORKING_CXX_BUILTIN_CONSTANT_P is defined.
	* config.in: Regenerated.
	* configure: Likewise.

gcc/testsuite/

	PR c++/69399
	* gcc.dg/torture/pr69399.c: New test.

5 files changed, 97 insertions, 5 deletions

diff --git a/gcc/config.in b/gcc/config.in
index 53352580b69..44db08990ce 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1775,6 +1775,13 @@
 #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
diff --git a/gcc/configure b/gcc/configure
index 3c9279593f1..cc4b02d3c00 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -6340,6 +6340,43 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
+# 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_c_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
+
 
 
 
@@ -16134,7 +16171,7 @@ _LT_EOF
 	if $NM -V 2>&1 | $GREP 'GNU' > /dev/null; then
 	  export_symbols_cmds='$NM -Bpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "W")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
 	else
-	  export_symbols_cmds='$NM -BCpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
+	  export_symbols_cmds='$NM -BCpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "L")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
 	fi
 	aix_use_runtimelinking=no
 
@@ -18162,7 +18199,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18165 "configure"
+#line 18202 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -18268,7 +18305,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18271 "configure"
+#line 18308 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -20620,7 +20657,7 @@ $as_echo_n "checking whether the $compiler linker ($LD) supports shared librarie
     if $NM -V 2>&1 | $GREP 'GNU' > /dev/null; then
       export_symbols_cmds_CXX='$NM -Bpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "W")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
     else
-      export_symbols_cmds_CXX='$NM -BCpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
+      export_symbols_cmds_CXX='$NM -BCpg $libobjs $convenience | awk '\''{ if (((\$ 2 == "T") || (\$ 2 == "D") || (\$ 2 == "B") || (\$ 2 == "L")) && (substr(\$ 3,1,1) != ".")) { print \$ 3 } }'\'' | sort -u > $export_symbols'
     fi
     ;;
   pw32*)
diff --git a/gcc/configure.ac b/gcc/configure.ac
index d41408143a1..b7b0bfeb98a 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -346,6 +346,33 @@ struct X<long long> { typedef long long t; };
 fi
 AC_LANG_POP(C++)
 
+# 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
+
 
 
 
diff --git a/gcc/system.h b/gcc/system.h
index 94d8138c020..3c5863caad6 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -726,7 +726,7 @@ 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 00000000000..3e171695c52
--- /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;
+}