Re: having trouble with define_split

["Denis Chertykov" <chertykov at gmail dot com>]

2009/1/9 Sean D'Epagnier <geckosenator@gmail.com>:
> Hi,
>
> I am currently working on adding native fixed-point support to the avr
> backend.  A lot of stuff is working, but there are a few things left,
> one of them is conversions from fixed point to floating point.
>
> I have conversions between all integer and fixed point types working
> as well as SA to SF conversion.
>
> I want to convert the fixed point types smaller than SA to float by
> using define_split to convert to SA then to SF.  I am first trying to
> get QQ->SF working, one of the things I tried is:
>
> (define_expand "fractqqsf2"
>  [(set (match_operand:SF 0 "register_operand" "")
>        (fract_convert:SF (match_operand:QQ 1 "register_operand" "")))
>   (clobber (match_operand:SA 2 "register_operand" ""))]
>  ""
>  "")

Wrong expand.

- (clobber (match_operand:SA 2 "register_operand" ""))]
+ (clobber (match_scratch:SA 2 ""))]


>
> (define_split
>  [(set (match_operand:SF 0 "register_operand" "")
>        (fract_convert:SF (match_operand:QQ 1 "register_operand" "")))
>   (clobber (match_operand:SA 2 "register_operand" ""))]
>  ""
>  [(set (match_dup 2) (fract_convert:SA (match_dup 1)))
>   (set (match_dup 0) (fract_convert:SF (match_dup 2)))]
> "")

(define_split
 [(set (match_operand:SF 0 "register_operand" "")
       (fract_convert:SF (match_operand:QQ 1 "register_operand" "")))
  (clobber (match_scratch:SA 2 "=r"))]]
 "reload_completed"
 [(set (match_dup 2) (fract_convert:SA (match_dup 1)))
  (set (match_dup 0) (fract_convert:SF (match_dup 2)))]
"")



>
> This causes the compiler to crash with a segmentation fault.  I have
> tried a bunch of other strategies, and usually the compiler complains
> about unrecognized instruction.  I'm not sure what I'm doing wrong,
> but I don't have a good reference example for this.  I can implement
> these routines in a library, that might end up being better in terms
> of space, but I would like to know what I am doing wrong and how to
> use define_split correctly.

May be better to define expand like this:

(define_expand "fractqqsf2"
  [(set (match_dup 2) (fract_convert:SA (match_operand:QQ 1
"register_operand" "")))
   (set (match_operand:SF 0 "register_operand" "") (fract_convert:SF
(match_dup 2)))]
  ""
  "
  operands[2] = gen_reg_rtx (SAmode);
  ")


Denis.