Since inline_secondary_memory_needed has

  /* ??? This is a lie.  We do have moves between mmx/general, and for
     mmx/sse2.  But by saying we need secondary memory we discourage the
     register allocator from using the mmx registers unless needed.  */
  if (MMX_CLASS_P (class1) != MMX_CLASS_P (class2))
    return true;

moves between MMX and non-MMX units require secondary memory.   There
is no need to check moves between MMX and integer units.

struct processor_costs has:

  const int mmxsse_to_integer;  /* cost of moving mmxsse register to
                                   integer.  */
  const int ssemmx_to_integer;  /* cost of moving integer to mmxsse register. */

This patch also renames mmxsse_to_integer to sse_to_integer and
ssemmx_to_integer to integer_to_sse.

Tested on Linux/x86-64.

	PR target/90877
	* config/i386/i386-features.c
	(dimode_scalar_chain::compute_convert_gain): Replace
	mmxsse_to_integer with sse_to_integer.
	* config/i386/i386.c (ix86_register_move_cost): Verify that
	moves between MMX and non-MMX units require secondary memory.
	Correct costs of moves between SSE and integer units.
	* config/i386/i386.h (processor_costs): Rename cost of moving
	SSE register to integer to sse_to_integer.  Rename cost of
	moving integer register to SSE to integer_to_sse.

From-SVN: r272294