On Mon, Oct 23, 2017 at 1:27 PM, Richard Sandiford
<richard.sandif...@linaro.org> wrote:
> This patch adds a helper routine (interesting_mode_p) to lower-subreg.c,
> to make the decision about whether a mode can be split and, if so,
> calculate the number of bytes and words in the mode. At present this
> function always returns true; a later patch will add cases in which it
> can return false.
Ok.
Richard.
>
> 2017-10-23 Richard Sandiford <richard.sandif...@linaro.org>
> Alan Hayward <alan.hayw...@arm.com>
> David Sherwood <david.sherw...@arm.com>
>
> gcc/
> * lower-subreg.c (interesting_mode_p): New function.
> (compute_costs, find_decomposable_subregs, decompose_register)
> (simplify_subreg_concatn, can_decompose_p, resolve_simple_move)
> (resolve_clobber, dump_choices): Use it.
>
> Index: gcc/lower-subreg.c
> ===================================================================
> --- gcc/lower-subreg.c 2017-10-23 11:47:11.274393237 +0100
> +++ gcc/lower-subreg.c 2017-10-23 11:47:23.555013148 +0100
> @@ -103,6 +103,18 @@ #define twice_word_mode \
> #define choices \
> this_target_lower_subreg->x_choices
>
> +/* Return true if MODE is a mode we know how to lower. When returning true,
> + store its byte size in *BYTES and its word size in *WORDS. */
> +
> +static inline bool
> +interesting_mode_p (machine_mode mode, unsigned int *bytes,
> + unsigned int *words)
> +{
> + *bytes = GET_MODE_SIZE (mode);
> + *words = CEIL (*bytes, UNITS_PER_WORD);
> + return true;
> +}
> +
> /* RTXes used while computing costs. */
> struct cost_rtxes {
> /* Source and target registers. */
> @@ -199,10 +211,10 @@ compute_costs (bool speed_p, struct cost
> for (i = 0; i < MAX_MACHINE_MODE; i++)
> {
> machine_mode mode = (machine_mode) i;
> - int factor = GET_MODE_SIZE (mode) / UNITS_PER_WORD;
> - if (factor > 1)
> + unsigned int size, factor;
> + if (interesting_mode_p (mode, &size, &factor) && factor > 1)
> {
> - int mode_move_cost;
> + unsigned int mode_move_cost;
>
> PUT_MODE (rtxes->target, mode);
> PUT_MODE (rtxes->source, mode);
> @@ -469,10 +481,10 @@ find_decomposable_subregs (rtx *loc, enu
> continue;
> }
>
> - outer_size = GET_MODE_SIZE (GET_MODE (x));
> - inner_size = GET_MODE_SIZE (GET_MODE (inner));
> - outer_words = (outer_size + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
> - inner_words = (inner_size + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
> + if (!interesting_mode_p (GET_MODE (x), &outer_size, &outer_words)
> + || !interesting_mode_p (GET_MODE (inner), &inner_size,
> + &inner_words))
> + continue;
>
> /* We only try to decompose single word subregs of multi-word
> registers. When we find one, we return -1 to avoid iterating
> @@ -507,7 +519,7 @@ find_decomposable_subregs (rtx *loc, enu
> }
> else if (REG_P (x))
> {
> - unsigned int regno;
> + unsigned int regno, size, words;
>
> /* We will see an outer SUBREG before we see the inner REG, so
> when we see a plain REG here it means a direct reference to
> @@ -527,7 +539,8 @@ find_decomposable_subregs (rtx *loc, enu
>
> regno = REGNO (x);
> if (!HARD_REGISTER_NUM_P (regno)
> - && GET_MODE_SIZE (GET_MODE (x)) > UNITS_PER_WORD)
> + && interesting_mode_p (GET_MODE (x), &size, &words)
> + && words > 1)
> {
> switch (*pcmi)
> {
> @@ -567,15 +580,15 @@ find_decomposable_subregs (rtx *loc, enu
> decompose_register (unsigned int regno)
> {
> rtx reg;
> - unsigned int words, i;
> + unsigned int size, words, i;
> rtvec v;
>
> reg = regno_reg_rtx[regno];
>
> regno_reg_rtx[regno] = NULL_RTX;
>
> - words = GET_MODE_SIZE (GET_MODE (reg));
> - words = (words + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
> + if (!interesting_mode_p (GET_MODE (reg), &size, &words))
> + gcc_unreachable ();
>
> v = rtvec_alloc (words);
> for (i = 0; i < words; ++i)
> @@ -599,25 +612,29 @@ decompose_register (unsigned int regno)
> simplify_subreg_concatn (machine_mode outermode, rtx op,
> unsigned int byte)
> {
> - unsigned int inner_size;
> + unsigned int outer_size, outer_words, inner_size, inner_words;
> machine_mode innermode, partmode;
> rtx part;
> unsigned int final_offset;
>
> + innermode = GET_MODE (op);
> + if (!interesting_mode_p (outermode, &outer_size, &outer_words)
> + || !interesting_mode_p (innermode, &inner_size, &inner_words))
> + gcc_unreachable ();
> +
> gcc_assert (GET_CODE (op) == CONCATN);
> - gcc_assert (byte % GET_MODE_SIZE (outermode) == 0);
> + gcc_assert (byte % outer_size == 0);
>
> - innermode = GET_MODE (op);
> - gcc_assert (byte < GET_MODE_SIZE (innermode));
> - if (GET_MODE_SIZE (outermode) > GET_MODE_SIZE (innermode))
> + gcc_assert (byte < inner_size);
> + if (outer_size > inner_size)
> return NULL_RTX;
>
> - inner_size = GET_MODE_SIZE (innermode) / XVECLEN (op, 0);
> + inner_size /= XVECLEN (op, 0);
> part = XVECEXP (op, 0, byte / inner_size);
> partmode = GET_MODE (part);
>
> final_offset = byte % inner_size;
> - if (final_offset + GET_MODE_SIZE (outermode) > inner_size)
> + if (final_offset + outer_size > inner_size)
> return NULL_RTX;
>
> /* VECTOR_CSTs in debug expressions are expanded into CONCATN instead of
> @@ -801,9 +818,10 @@ can_decompose_p (rtx x)
>
> if (HARD_REGISTER_NUM_P (regno))
> {
> - unsigned int byte, num_bytes;
> + unsigned int byte, num_bytes, num_words;
>
> - num_bytes = GET_MODE_SIZE (GET_MODE (x));
> + if (!interesting_mode_p (GET_MODE (x), &num_bytes, &num_words))
> + return false;
> for (byte = 0; byte < num_bytes; byte += UNITS_PER_WORD)
> if (simplify_subreg_regno (regno, GET_MODE (x), byte, word_mode)
> < 0)
> return false;
> @@ -826,14 +844,15 @@ resolve_simple_move (rtx set, rtx_insn *
> rtx src, dest, real_dest;
> rtx_insn *insns;
> machine_mode orig_mode, dest_mode;
> - unsigned int words;
> + unsigned int orig_size, words;
> bool pushing;
>
> src = SET_SRC (set);
> dest = SET_DEST (set);
> orig_mode = GET_MODE (dest);
>
> - words = (GET_MODE_SIZE (orig_mode) + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
> + if (!interesting_mode_p (orig_mode, &orig_size, &words))
> + gcc_unreachable ();
> gcc_assert (words > 1);
>
> start_sequence ();
> @@ -964,7 +983,7 @@ resolve_simple_move (rtx set, rtx_insn *
> {
> unsigned int i, j, jinc;
>
> - gcc_assert (GET_MODE_SIZE (orig_mode) % UNITS_PER_WORD == 0);
> + gcc_assert (orig_size % UNITS_PER_WORD == 0);
> gcc_assert (GET_CODE (XEXP (dest, 0)) != PRE_MODIFY);
> gcc_assert (GET_CODE (XEXP (dest, 0)) != POST_MODIFY);
>
> @@ -1059,7 +1078,7 @@ resolve_clobber (rtx pat, rtx_insn *insn
> {
> rtx reg;
> machine_mode orig_mode;
> - unsigned int words, i;
> + unsigned int orig_size, words, i;
> int ret;
>
> reg = XEXP (pat, 0);
> @@ -1067,8 +1086,8 @@ resolve_clobber (rtx pat, rtx_insn *insn
> return false;
>
> orig_mode = GET_MODE (reg);
> - words = GET_MODE_SIZE (orig_mode);
> - words = (words + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
> + if (!interesting_mode_p (orig_mode, &orig_size, &words))
> + gcc_unreachable ();
>
> ret = validate_change (NULL_RTX, &XEXP (pat, 0),
> simplify_gen_subreg_concatn (word_mode, reg,
> @@ -1332,12 +1351,13 @@ dump_shift_choices (enum rtx_code code,
> static void
> dump_choices (bool speed_p, const char *description)
> {
> - unsigned int i;
> + unsigned int size, factor, i;
>
> fprintf (dump_file, "Choices when optimizing for %s:\n", description);
>
> for (i = 0; i < MAX_MACHINE_MODE; i++)
> - if (GET_MODE_SIZE ((machine_mode) i) > UNITS_PER_WORD)
> + if (interesting_mode_p ((machine_mode) i, &size, &factor)
> + && factor > 1)
> fprintf (dump_file, " %s mode %s for copy lowering.\n",
> choices[speed_p].move_modes_to_split[i]
> ? "Splitting"
