Re: arm_hard_regno_mode_ok update

[Nick Clifton <nickc at cambridge dot redhat dot com>]

Hi Richard,

> I don't think this code can't be right in general.  I really think a
> user needs to be able to name *any* reserved register in an ASM type
> statement.

 True.

>  Why is the check in there in the first place?  We didn't need it
>  before...

  Because I am trying to stop IP (r12) being assigned to hold a DImode
  value, since the upper half will be placed in the stack pointer
  (r13), which is not good.

  Anyway here is a patch which I think will do the right thing.

Cheers
        Nick

2002-01-25  Nick Clifton  <nickc@cambridge.redhat.com>

	* config/arm/arm.c (arm_hard_regno_mode_ok): Allow any general
	purpose register to hold an SImode (or smaller) value.

Index: config/arm/arm.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/arm/arm.c,v
retrieving revision 1.191
diff -c -3 -p -w -r1.191 arm.c
*** arm.c	2002/01/24 16:27:51	1.191
--- arm.c	2002/01/25 11:40:42
*************** arm_hard_regno_mode_ok (regno, mode)
*** 9139,9162 ****
      return (NUM_REGS (mode) < 2) || (regno < LAST_LO_REGNUM);
  
    if (regno <= LAST_ARM_REGNUM)
!     /* If the register is a general purpose ARM register we allow
!        it only if it not a special register (SP, LR, PC) and only
!        if there will be enough (non-special) registers to hold the
!        entire value.  */
!     {
!       /* As a special exception we allow an SImode value to be
! 	 "assigned" to the stack pointer.  This is not intended
! 	 to actually allow a value to be stored in the SP, but so
! 	 that the stack pointer can be referenced from C code like
! 	 this:
  	 
  	   register char * stack_ptr asm ("sp");
  
! 	 This expression is actually used in newlib...  */
!       if (mode == SImode && regno == SP_REGNUM)
! 	return 1;
!       return regno < (SP_REGNUM - (unsigned) NUM_REGS (mode));
!     }
  
    if (   regno == FRAME_POINTER_REGNUM
        || regno == ARG_POINTER_REGNUM)
--- 9139,9158 ----
      return (NUM_REGS (mode) < 2) || (regno < LAST_LO_REGNUM);
  
    if (regno <= LAST_ARM_REGNUM)
!     /* We allow an SImode or smaller value to be stored in any
!        general purpose register.  This does not mean, for example
!        that GCC will choose to store a variable in the stack pointer
!        since it is a fixed register.  But it is important to allow
!        access to these special registers, so that they can be
!        referenced from C code via the asm assembler alias, eg:
  
            register char * stack_ptr asm ("sp");
  
!        For any mode requiring more than one register to hold the
!        value we restrict the choice so that r13, r14, and r15
!        cannot be part of the register set.  */
!     return (NUM_REGS (mode) <= 1)
!       || (regno < (SP_REGNUM - (unsigned) NUM_REGS (mode)));
  
    if (   regno == FRAME_POINTER_REGNUM
        || regno == ARG_POINTER_REGNUM)