On 06/09/16 14:14, Wilco Dijkstra wrote:
> Improve aarch64_legitimize_address - avoid splitting the offset if it is
> supported. When we do split, take the mode size into account. BLKmode
> falls into the unaligned case but should be treated like LDP/STP.
> This improves codesize slightly due to fewer base address calculations:
>
> int f(int *p) { return p[5000] + p[7000]; }
>
> Now generates:
>
> f:
> add x0, x0, 16384
> ldr w1, [x0, 3616]
> ldr w0, [x0, 11616]
> add w0, w1, w0
> ret
>
> instead of:
>
> f:
> add x1, x0, 16384
> add x0, x0, 24576
> ldr w1, [x1, 3616]
> ldr w0, [x0, 3424]
> add w0, w1, w0
> ret
>
> OK for trunk?
>
> ChangeLog:
> 2016-09-06 Wilco Dijkstra <wdijk...@arm.com>
>
> gcc/
> * config/aarch64/aarch64.c (aarch64_legitimize_address):
> Avoid use of base_offset if offset already in range.
OK.
R.
> --
>
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index
> 27bbdbad8cddc576f9ed4fd0670116bd6d318412..119ff0aecb0c9f88899fa141b2c7f9158281f9c3
> 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -5058,9 +5058,19 @@ aarch64_legitimize_address (rtx x, rtx /* orig_x */,
> machine_mode mode)
> /* For offsets aren't a multiple of the access size, the limit is
> -256...255. */
> else if (offset & (GET_MODE_SIZE (mode) - 1))
> - base_offset = (offset + 0x100) & ~0x1ff;
> + {
> + base_offset = (offset + 0x100) & ~0x1ff;
> +
> + /* BLKmode typically uses LDP of X-registers. */
> + if (mode == BLKmode)
> + base_offset = (offset + 512) & ~0x3ff;
> + }
> + /* Small negative offsets are supported. */
> + else if (IN_RANGE (offset, -256, 0))
> + base_offset = 0;
> + /* Use 12-bit offset by access size. */
> else
> - base_offset = offset & ~0xfff;
> + base_offset = offset & (~0xfff * GET_MODE_SIZE (mode));
>
> if (base_offset != 0)
> {
>
