Hi!
The following testcase ICEs, because when !HONOR_NANS but
HONOR_SIGNED_ZEROS, if we see
lhs = op1 * op2;
and know that lhs is [-0.0, 0.0] and op2 is [0.0, 0.0], the
division of these two yields UNDEFINED and clear_nan () on it
fails an assert. With HONOR_NANS it would actually result in
a known NAN, but when NANs aren't honored, we clear the NAN bits.
Now, for the above case we actually don't know anything about
the op1 range (except that it isn't a NAN/INF because of
!HONOR_NANS !HONOR_INFINITIES), so I think the best is just
to return VARYING for the case we get UNDEFINED as well.
If we want, the op[12]_range methods perhaps can handle the
corner cases earlier separately, say for
lhs [0.0, 0.0] and op2 [0.0, 0.0] when HONOR_SIGNED_ZEROS this
would be just [0.0, MAX].
Bootstrapped/regtested on x86_64-linux and i686-linux, preapproved by
Aldy in the PR, committed to trunk.
2022-11-16 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/107668
* range-op-float.cc (float_binary_op_range_finish): Set VARYING
also when r is UNDEFINED.
* gcc.dg/ubsan/pr107668.c: New test.
--- gcc/range-op-float.cc.jj 2022-11-14 19:33:32.514881313 +0100
+++ gcc/range-op-float.cc 2022-11-15 09:25:57.956137343 +0100
@@ -1891,8 +1891,9 @@ float_binary_op_range_finish (bool ret,
// or the reverse operation introduced a known NAN.
// Say for lhs = op1 * op2 if lhs is [-0, +0] and op2 is too,
// 0 / 0 is known NAN. Just punt in that case.
+ // If NANs aren't honored, we get for 0 / 0 UNDEFINED, so punt as well.
// Or if lhs is a known NAN, we also don't know anything.
- if (r.known_isnan () || lhs.known_isnan ())
+ if (r.known_isnan () || lhs.known_isnan () || r.undefined_p ())
{
r.set_varying (type);
return true;
--- gcc/testsuite/gcc.dg/ubsan/pr107668.c.jj 2022-11-15 09:24:40.281189629
+0100
+++ gcc/testsuite/gcc.dg/ubsan/pr107668.c 2022-11-15 09:24:40.281189629
+0100
@@ -0,0 +1,12 @@
+/* PR tree-optimization/107668 */
+/* { dg-do compile } */
+/* { dg-options "-ffast-math -fno-associative-math
-fsanitize=float-cast-overflow -fno-guess-branch-probability -fsigned-zeros" }
*/
+
+_Complex int c;
+int i;
+
+void
+foo (void)
+{
+ c /= (_Complex) i;
+}
Jakub
