[patch] ivopts fixes

[David Edelsohn]

	Even with these fixes, I still am seeing some failures that appear
to be due to the new ivopts optimizations.  In SPEC CPU2000 164.gzip does
not build due to an ICE in emit_move_insn() whose backtrace leads to
ivopts.

	I have created PR 17531 for the bug and Dan has attached a
minimized testcase.  This might be related to PR 17474, but I don't want
to assume that it is a duplicate.  And debugging with the C testcase may
be easier.

David