Constrain not satisfied - floating point insns.

[Rohit Arul Raj]

Hi all,

I am currently adding floating point support for a private target (for
GCC 4.1.1). i am having some problems with register allocation.

In SF mode, i have specified to the compiler that it can use both
floating point registers as well as data registers. For all move
instructions in SF mode, i can use both these registers. But while
moving data from/to memory, i can use only floating point registers.

(define_expand "movsf"
  [(set (match_operand:SF 0 "general_operand" "")
        (match_operand:SF 1 "general_operand" ""))]
  ""
  "
  {
  if (GET_CODE (operands[0]) == MEM) {
    operands[1] = force_reg (SFmode, operands[1]);
})

(define_insn "movsf_store"
  [(set (match_operand:SF 0 "memory_operand"  "=m")
	(match_operand:SF 1 "float_reg"    "f"))]
   ""
  "stf \\t%1, %0"
 )

But if the compiler tries to move a data register to memory, i get
constraint not satisfied error (ICE).

1. Is there any way to prevent the compiler from using data registers.
2. As a work around, i did the following:
   a) In define expand, i check whether the register is a data register.
   b) If it is a data register,  generate a callee saved register
(floating point register).
   c) Emit a move insn from data register to floating pt register.
   d) Change the second operand to floating point register so that my
define_insn pattern is matched properly.

Is it advisable to follow this method or is there a better way to
handle this problem?

Regards,
Rohit