[tree-ssa] DCE and conditionals

[law@redhat.com]

In message <20030505201105.GA28303@tornado.toronto.redhat.com>, Diego Novillo w
rites:
 >On Mon, May 05, 2003 at 08:31:47AM -0400, Andrew MacLeod wrote:
 >After fixing the flow graph linearizer, this should be converted
 >into:
 >
 >	if ((void)0)
 >	  (void)0;
 >	else
 >	  (void)0;
 >	lab:
 >	  a_5 = PHI <a_1, a_0, a_4>
 >
 >Note how the COND_EXPR is only kept because it provides the
 >structure needed to feed that PHI node.  If all 'a's coalesce
 >together, then SSA->normal could remove the empty skeleton for
 >the if().
The useless crud zapper already catches this (yes, I'm finally
back from our little adventure in sin city).

jeff