tree-optimization/112282 - wrong-code with ifcvt hoisting

tree-optimization/112282 - wrong-code with ifcvt hoisting

The following avoids hoisting of invariants from conditionally
executed parts of an if-converted loop.  That now makes a difference
since we perform bitfield lowering even when we do not actually
if-convert the loop.  if-conversion deals with resetting flow-sensitive
info when necessary already.

	PR tree-optimization/112282
	* tree-if-conv.cc (ifcvt_hoist_invariants): Only hoist from
	the loop header.

	* gcc.dg/torture/pr112282.c: New testcase.