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Re: [PATCH][AArch64] Simplify aarch64_can_eliminate
- From: James Greenhalgh <james dot greenhalgh at arm dot com>
- To: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, nd <nd at arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>
- Date: Tue, 7 Nov 2017 17:11:27 +0000
- Subject: Re: [PATCH][AArch64] Simplify aarch64_can_eliminate
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On Tue, Aug 15, 2017 at 05:25:06PM +0100, Wilco Dijkstra wrote:
>
> ping
>
>
> From: Wilco Dijkstra
> Sent: 07 August 2017 15:13
> To: GCC Patches; James Greenhalgh
> Cc: nd; Richard Earnshaw
> Subject: [PATCH][AArch64] Simplify aarch64_can_eliminate
>
> Simplify aarch64_can_eliminate - if we need a frame pointer, we must
> eliminate to HARD_FRAME_POINTER_REGNUM. Rather than hardcoding all
> combinations from the ELIMINABLE_REGS list, just do the correct check.
>
> ChangeLog:
> 2017-08-07 Wilco Dijkstra <wdijkstr@arm.com>
>
> gcc/
> * config/aarch64/aarch64.c (aarch64_can_eliminate): Simplify logic.
> --
>
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index 9463edf63ffe770062b4120fada090e20c93a269..fbb4244cb58d2a25203aa27342c2f7988c30bd98 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -5858,26 +5858,12 @@ aarch64_secondary_reload (bool in_p ATTRIBUTE_UNUSED, rtx x,
> }
>
> static bool
> -aarch64_can_eliminate (const int from, const int to)
> +aarch64_can_eliminate (const int from ATTRIBUTE_UNUSED, const int to)
> {
> - /* If we need a frame pointer, we must eliminate FRAME_POINTER_REGNUM into
> - HARD_FRAME_POINTER_REGNUM and not into STACK_POINTER_REGNUM. */
> -
> + /* If we need a frame pointer, ARG_POINTER_REGNUM and FRAME_POINTER_REGNUM
> + can only eliminate to HARD_FRAME_POINTER_REGNUM. */
Please add an assert in here,
(from == ARG_POINTER_REGNUM || from == FRAME_POINTER_REGNUM)
Otherwise, OK (please test this against a recent trunk).
Reviewed-By: James Greenhalgh <james.greenhalgh@arm.com>
Thanks,
James
> if (frame_pointer_needed)
> - {
> - if (from == ARG_POINTER_REGNUM && to == HARD_FRAME_POINTER_REGNUM)
> - return true;
> - if (from == ARG_POINTER_REGNUM && to == STACK_POINTER_REGNUM)
> - return false;
> - if (from == FRAME_POINTER_REGNUM && to == STACK_POINTER_REGNUM
> - && !cfun->calls_alloca)
> - return true;
> - if (from == FRAME_POINTER_REGNUM && to == HARD_FRAME_POINTER_REGNUM)
> - return true;
> -
> - return false;
> - }
> -
> + return to == HARD_FRAME_POINTER_REGNUM;
> return true;
> }