http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48970
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> 2011-05-11 21:23:45
UTC ---
Also
const int mmxsse_to_integer; /* cost of moving mmxsse register to
integer and vice versa. */
isn't limited to integers:
/* Moves between SSE/MMX and integer unit are expensive. */
if (MMX_CLASS_P (class1) != MMX_CLASS_P (class2)
|| SSE_CLASS_P (class1) != SSE_CLASS_P (class2))
/* ??? By keeping returned value relatively high, we limit the number
of moves between integer and MMX/SSE registers for all targets.
Additionally, high value prevents problem with x86_modes_tieable_p(),
where integer modes in MMX/SSE registers are not tieable
because of missing QImode and HImode moves to, from or between
MMX/SSE registers. */
return MAX (8, ix86_cost->mmxsse_to_integer);
Integer register classes aren't checked at all.
