On Wed, Jun 15, 2016 at 08:08:22AM -0600, Martin Sebor wrote:
> I like the idea of being able to use the built-ins for this, but
> I think it would be confusing for them to follow subtly different
> rules for C than for C++. Since the value of the last argument
Here is incremental patch to the patch I've posted earlier today,
which doesn't promote the last argument of __builtin_*_overflow_p
and thus for bitfields it behaves pretty much like the C FE.
Bootstrapped/regtested (together with the other patch) on x86_64-linux and
i686-linux, ok for trunk?
2016-06-15 Jakub Jelinek <ja...@redhat.com>
* call.c (magic_varargs_p): Return 3 for __builtin_*_overflow_p.
(build_over_call): For magic == 3, do no conversion only on 3rd
argument.
* c-c++-common/torture/builtin-arith-overflow-p-19.c: Run for C++ too.
* g++.dg/ext/builtin-arith-overflow-2.C: New test.
--- gcc/cp/call.c.jj 2016-06-15 09:17:22.000000000 +0200
+++ gcc/cp/call.c 2016-06-15 17:06:57.097793446 +0200
@@ -7132,7 +7132,8 @@ convert_for_arg_passing (tree type, tree
which just decay_conversion or no conversions at all should be done.
This is true for some builtins which don't act like normal functions.
Return 2 if no conversions at all should be done, 1 if just
- decay_conversion. */
+ decay_conversion. Return 3 for special treatment of the 3rd argument
+ for __builtin_*_overflow_p. */
int
magic_varargs_p (tree fn)
@@ -7149,6 +7150,11 @@ magic_varargs_p (tree fn)
case BUILT_IN_VA_START:
return 1;
+ case BUILT_IN_ADD_OVERFLOW_P:
+ case BUILT_IN_SUB_OVERFLOW_P:
+ case BUILT_IN_MUL_OVERFLOW_P:
+ return 3;
+
default:;
return lookup_attribute ("type generic",
TYPE_ATTRIBUTES (TREE_TYPE (fn))) != 0;
@@ -7606,14 +7612,14 @@ build_over_call (struct z_candidate *can
for (; arg_index < vec_safe_length (args); ++arg_index)
{
tree a = (*args)[arg_index];
- if (magic == 2)
+ if ((magic == 3 && arg_index == 2) || magic == 2)
{
/* Do no conversions for certain magic varargs. */
a = mark_type_use (a);
if (TREE_CODE (a) == FUNCTION_DECL && reject_gcc_builtin (a))
return error_mark_node;
}
- else if (magic == 1)
+ else if (magic != 0)
/* For other magic varargs only do decay_conversion. */
a = decay_conversion (a, complain);
else if (DECL_CONSTRUCTOR_P (fn)
--- gcc/testsuite/c-c++-common/torture/builtin-arith-overflow-p-19.c.jj
2016-06-15 17:13:29.839717235 +0200
+++ gcc/testsuite/c-c++-common/torture/builtin-arith-overflow-p-19.c
2016-06-15 13:05:21.000000000 +0200
@@ -1,5 +1,5 @@
/* Test __builtin_{add,sub,mul}_overflow_p. */
-/* { dg-do run { target c } } */
+/* { dg-do run } */
/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */
#include "builtin-arith-overflow.h"
--- gcc/testsuite/g++.dg/ext/builtin-arith-overflow-2.C.jj 2016-06-15
17:34:37.617298196 +0200
+++ gcc/testsuite/g++.dg/ext/builtin-arith-overflow-2.C 2016-06-15
17:34:11.000000000 +0200
@@ -0,0 +1,53 @@
+// { dg-do run }
+// { dg-options "-O2" }
+
+struct A { int i : 1; };
+struct B { int j : 3; };
+
+template <typename S>
+int
+foo (int x, int y)
+{
+ A a = {};
+ S s = {};
+ return __builtin_add_overflow_p (x, y, a.i) + 2 * __builtin_mul_overflow_p
(x, y, s.j);
+}
+
+__attribute__((noinline, noclone)) int
+bar (int x, int y)
+{
+ return foo <B> (x, y);
+}
+
+#if __cplusplus >= 201402L
+template <typename S>
+constexpr int
+baz (int x, int y)
+{
+ A a = {};
+ S s = {};
+ return __builtin_add_overflow_p (x, y, a.i) + 2 * __builtin_mul_overflow_p
(x, y, s.j);
+}
+
+constexpr int t1 = baz <B> (0, 0);
+constexpr int t2 = baz <B> (1, -1);
+constexpr int t3 = baz <B> (1, -4);
+constexpr int t4 = baz <B> (-4, 4);
+constexpr int t5 = baz <B> (4, 2);
+static_assert (t1 == 0, "");
+static_assert (t2 == 0, "");
+static_assert (t3 == 1, "");
+static_assert (t4 == 2, "");
+static_assert (t5 == 3, "");
+#endif
+
+int
+main ()
+{
+ if (bar (0, 0) != 0
+ || bar (-1, 1) != 0
+ || bar (-4, 1) != 1
+ || bar (4, -4) != 2
+ || bar (2, 4) != 3)
+ __builtin_abort ();
+}
Jakub
