[PATCH] ARM: exclude fixed_regs for stack-alignment save/restore

[Richard Earnshaw]

On 17/07/12 21:42, Roland McGrath wrote:
> Richard, here is the patch against the current trunk, as I promised
> last week in Prague.  Please apply.
> 

Done.

I've tweaked the comments slightly, but the functional modification is
unchanged.

R.

> 
> Thanks,
> Roland
> 
> 
> gcc/
> 2012-07-17  Roland McGrath  <mcgrathr@google.com>
> 
> 	* config/arm/arm.c (arm_get_frame_offsets): Never use a fixed register
> 	as the extra register to save/restore for stack-alignment padding.
> 
> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> index e2f625c..189f71e 100644
> --- a/gcc/config/arm/arm.c
> +++ b/gcc/config/arm/arm.c
> @@ -16121,7 +16121,12 @@ arm_get_frame_offsets (void)
>  	  else
>  	    for (i = 4; i <= (TARGET_THUMB1 ? LAST_LO_REGNUM : 11); i++)
>  	      {
> -		if ((offsets->saved_regs_mask & (1 << i)) == 0)
> +		/* While the gratuitous register save/restore is ordinarily
> +		   harmless, if a register is marked as fixed or global it
> +		   may be entirely forbidden by the system ABI to touch it,
> +		   so we should avoid those registers.  */
> +		if (!fixed_regs[i]
> +		    && (offsets->saved_regs_mask & (1 << i)) == 0)
>  		  {
>  		    reg = i;
>  		    break;
>