How to require an extra register in define_split?

[Terry Guo <flameroc@xxxxxxxxx>]

Hi there,

For define_peephole2, one can use (match_scratch:SI 2 "r") to require an
extra scratch register. I am wondering whether it is possible to require an
extra register for define_split?

I am trying to split following RTL into more than one RTLs and thus need an
extra register.

(define_split
  [(set (match_operand:SF 0 "register_operand")
        (match_operand:SF 1 "const_double_operand"))]
.................
)

The above define_split can match its targets, but following will fail to
match:

(define_split
  [(set (match_operand:SF 0 "register_operand")
        (match_operand:SF 1 "const_double_operand"))
   (clobber (match_scratch:SI 2 "register_operand"))]
............
)

Could some one please help? Thanks in advance.

BR,
Terry