tree-optimization/121720 - missed PRE hoisting

tree-optimization/121720 - missed PRE hoisting

The following re-implements the fix for PR84830 where the original
fix causes missed optimizations.  The issue with PR84830 is that
we end up growing ANTIC_IN value set during iteration which happens
because we conditionally prune values based on ANTIC_OUT - TMP_GEN
expressions.  But when ANTIC_OUT was computed including the
MAX set on one edge we fail to take into account the implicitly
represented MAX expression set.  The following rectifies this by
not pruning the value set in bitmap_set_subtract_expressions in
such case.  This avoids the pruning from the ANTIC_IN value
set when MAX is involved and thus later growing, removing the
need to explicitly prune it with the last iteration set.

	PR tree-optimization/121720
	* tree-ssa-pre.cc (bitmap_set_subtract_expressions): Add
	flag to tell whether we should copy instead of prune the
	value set.
	(compute_antic_aux): Remove intersection of ANTIC_IN with
	the old solution.  When subtracting TMP_GEN from
	ANTIC_OUT do not prune the value set when MAX was involved
	in the ANTIC_OUT computation.

	* gcc.dg/tree-ssa/ssa-pre-36.c: New testcase.