i386.md floating point comparison with general register

[John Wehle]

I'm looking at improving the i386 floating point comparision
patterns and am curious about:

  [(set (cc0)
        (match_operator 2 "VOIDmode_compare_op"
                        [(match_operand:XF 0 "register_operand" "f")
                         (float:XF
                          (match_operand:SI 1 "nonimmediate_operand" "rm"))]))

Which appears to be a pattern for the benefit of combine.  What seems odd is
the pattern allows the comparison of a floating point register with a general
register which the i386 doesn't actually support.  It's currently implement
by having output_float_compare load the general register into a floating point
register and then doing the comparison.  Why is it useful to hide this move
from gcc?  Should this pattern perhaps be:

  [(set (cc0)
        (match_operator 2 "VOIDmode_compare_op"
                        [(match_operand:XF 0 "register_operand" "f")
                         (float:XF
                          (match_operand:SI 1 "memory_operand" "m"))]))

-- John
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