https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101186
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |85316
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The complication is that the a == b equivalence has to be taken into account to
relate the c < a and c >= b relations.
Maybe the new relation code can do sth here, but confirmed on trunk.
void g (int a, int b, int x, int y)
{
int c = y;
if (a != 0)
c = x;
while (b < 1000)
// without this loop, jump thread & VRP can remove dead code
{
if (a != 0)
{
if (c > x)
printf ("Unreachable!");
}
that's also a classical example for predicated value-numbering (which we
don't implement).
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases
