Re: tree-ssa: a weird (mis)optimization

[Andrew Haley <aph at redhat dot com>]

Geert Bosch writes:
 > On Nov 30, 2004, at 11:07, Andrew Haley wrote:
 > > The problem here is that the line
 > >
 > >   <tmp>_4 = x_3->length;
 > >
 > > has disappeared.  This should not have happened, because the operation
 > > should have may_trap_p() set -- we're deleting a trapping instruction.
 > 
 > Does Java require a trap here, even if the result is not needed
 > and the entire expression could otherwise be deleted?

Yes.

 > If Java prevents such removal, we should find a way to express
 > that so other languages don't lose the optimization.

Well, as far as I can see this is simply a bug.  There is already
plenty of code in the compiler to make sure trapping insns aren't
deleted.

Andrew.