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Re: [PATCH ARM]Handle REG addressing mode in output_move_neon explicitly
- From: Richard Earnshaw <rearnsha at arm dot com>
- To: "bin.cheng" <bin dot cheng at arm dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 01 May 2014 15:03:23 +0100
- Subject: Re: [PATCH ARM]Handle REG addressing mode in output_move_neon explicitly
- Authentication-results: sourceware.org; auth=none
- References: <002f01cf6357$854c7a00$8fe56e00$ at arm dot com>
On 29/04/14 04:02, bin.cheng wrote:
> Hi,
> Function output_move_neon now generates vld1.64 for memory ref like "dx <-
> [r1:SI]", this is bogus because it requires at least 64-bit alignment for
> 32-bit aligned memory ref. It works now because GCC doesn't generate such
> insns in the first place, but things are going to change if memset/memcpy
> calls are inlined by using neon instructions.
>
V[LD/ST]1.64 only need to be 64-bit aligned if strict alignment is
enabled. We normally assume that not to be the case. The exception to
this is when an explicit alignment check is used in the address
expression (the :64 suffix), which causes the address to be checked for
strict alignment at all times.
Do you have a testcase?
R.
> This patch fixes the issue by generating ldr for such instructions.
>
> Bootstrapped on cortex-a15 with neon.
> Is it OK?
>
> Thanks,
> bin
>
>
> 2014-04-29 Bin Cheng <bin.cheng@arm.com>
>
> * config/arm/arm.c (output_move_neon): Handle REG explicitly.
>
>
> output_move_neon-20140429.txt
>
>
> Index: gcc/config/arm/arm.c
> ===================================================================
> --- gcc/config/arm/arm.c (revision 209852)
> +++ gcc/config/arm/arm.c (working copy)
> @@ -18427,6 +18453,20 @@ output_move_neon (rtx *operands)
> /* FIXME: Not currently enabled in neon_vector_mem_operand. */
> gcc_unreachable ();
>
> + case REG:
> + /* We have to use vldm / vstm for too-large modes. */
> + if (nregs > 1)
> + {
> + if (nregs > 4)
> + templ = "v%smia%%?\t%%m0, %%h1";
> + else
> + templ = "v%s1.64\t%%h1, %%A0";
> +
> + ops[0] = mem;
> + ops[1] = reg;
> + break;
> + }
> + /* Fall through. */
> case LABEL_REF:
> case PLUS:
> {
> @@ -18460,14 +18500,7 @@ output_move_neon (rtx *operands)
> }
>
> default:
> - /* We have to use vldm / vstm for too-large modes. */
> - if (nregs > 4)
> - templ = "v%smia%%?\t%%m0, %%h1";
> - else
> - templ = "v%s1.64\t%%h1, %%A0";
> -
> - ops[0] = mem;
> - ops[1] = reg;
> + gcc_unreachable ();
> }
>
> sprintf (buff, templ, load ? "ld" : "st");
>