Re: [PATCH 1/5] Handle WORD_REGISTER_OPERATIONS when reloading (subreg(reg))

[Vladimir Makarov <vmakarov at redhat dot com>]

On 02/07/2017 09:08 AM, Matthew Fortune wrote:
> Hi,
>
> This change deals with reloading a subreg(reg) using the inner mode
> to prevent partial spilling of data like in the case described here:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78660#c8
>
> No test case for now but I am investigating a targeted test using
> the RTL frontend for later submission.
The patch is OK for the trunk.  Thanks.
> gcc/
> 	PR target/78660
> 	* lra-constraints.c (curr_insn_transform): Handle
> 	WORD_REGISTER_OPERATIONS requirements when reloading SUBREGs.
> ---
>   gcc/lra-constraints.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
> index 22323b2..f29308f 100644
> --- a/gcc/lra-constraints.c
> +++ b/gcc/lra-constraints.c
> @@ -4130,7 +4130,14 @@ curr_insn_transform (bool check_only_p)
>   			  && (goal_alt[i] == NO_REGS
>   			      || (simplify_subreg_regno
>   				  (ira_class_hard_regs[goal_alt[i]][0],
> -				   GET_MODE (reg), byte, mode) >= 0)))))
> +				   GET_MODE (reg), byte, mode) >= 0)))
> +		      /* WORD_REGISTER_OPERATIONS targets require the register
> +			 to be reloaded when the outer mode is strictly
> +			 narrower than the inner mode.  Note: It may be
> +			 necessary to always reload the inner mode here but it
> +			 requires further investigation.  */
> +		      || (GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (reg))
> +			  && WORD_REGISTER_OPERATIONS)))
>   		{
>   		  if (type == OP_OUT)
>   		    type = OP_INOUT;