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Re: Simplify pad_below implementation
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Sandiford <richard dot sandiford at linaro dot org>
- Date: Mon, 21 Aug 2017 14:57:20 +0200
- Subject: Re: Simplify pad_below implementation
- Authentication-results: sourceware.org; auth=none
- References: <874lt1dvgc.fsf@linaro.org>
On Mon, Aug 21, 2017 at 1:14 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> This patch simplifies the alignment calculations in pad_below.
> The first arm of the "if" was:
>
> - taking GET_MODE_BITSIZE (always equal to GET_MODE_SIZE * BITS_PER_UNIT),
> - rounding up to the next multiple of PARM_BOUNDARY
> - converting bits to bytes and
> - subtracting the GET_MODE_SIZE
>
> so was in effect calculating the number of bytes needed to round
> GET_MODE_SIZE up to (PARM_BOUNDARY / BITS_PER_UNIT). That can be
> done more directly as -size & (align - 1), which is easier to
> convert to variable-sized modes.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu, and by building
> one target per CPU and checking that there were no differences in
> assembly for the testsuite. OK to install?
Ok.
Richard.
> Richard
>
>
> 2017-08-21 Richard Sandiford <richard.sandiford@linaro.org>
> Alan Hayward <alan.hayward@arm.com>
> David Sherwood <david.sherwood@arm.com>
>
> gcc/
> * function.c (pad_below): Simplify padding calculation.
>
> Index: gcc/function.c
> ===================================================================
> --- gcc/function.c 2017-08-21 10:42:34.185530464 +0100
> +++ gcc/function.c 2017-08-21 11:55:41.018148268 +0100
> @@ -4322,21 +4322,16 @@ pad_to_arg_alignment (struct args_size *
> static void
> pad_below (struct args_size *offset_ptr, machine_mode passed_mode, tree sizetree)
> {
> + unsigned int align = PARM_BOUNDARY / BITS_PER_UNIT;
> if (passed_mode != BLKmode)
> - {
> - if (GET_MODE_BITSIZE (passed_mode) % PARM_BOUNDARY)
> - offset_ptr->constant
> - += (((GET_MODE_BITSIZE (passed_mode) + PARM_BOUNDARY - 1)
> - / PARM_BOUNDARY * PARM_BOUNDARY / BITS_PER_UNIT)
> - - GET_MODE_SIZE (passed_mode));
> - }
> + offset_ptr->constant += -GET_MODE_SIZE (passed_mode) & (align - 1);
> else
> {
> if (TREE_CODE (sizetree) != INTEGER_CST
> - || (TREE_INT_CST_LOW (sizetree) * BITS_PER_UNIT) % PARM_BOUNDARY)
> + || (TREE_INT_CST_LOW (sizetree) & (align - 1)) != 0)
> {
> /* Round the size up to multiple of PARM_BOUNDARY bits. */
> - tree s2 = round_up (sizetree, PARM_BOUNDARY / BITS_PER_UNIT);
> + tree s2 = round_up (sizetree, align);
> /* Add it in. */
> ADD_PARM_SIZE (*offset_ptr, s2);
> SUB_PARM_SIZE (*offset_ptr, sizetree);