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dse.c (find_shift_sequence): No-op rework of control flow.

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	* dse.c (find_shift_sequence): No-op rework of control flow.

From-SVN: r128614
This commit is contained in:
Richard Sandiford 2007-09-20 07:43:49 +00:00 committed by Richard Sandiford
parent 6d3b5aea0b
commit c6f3019a9a
2 changed files with 53 additions and 57 deletions
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4
gcc/ChangeLog
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@ -1,3 +1,7 @@
2007-09-20 Richard Sandiford <rsandifo@nildram.co.uk>
* dse.c (find_shift_sequence): No-op rework of control flow.
2007-09-19 Richard Sandiford <rsandifo@nildram.co.uk>
* config/mips/mips.c (build_mips16_call_stub): Tidy. Fix second

106
gcc/dse.c
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@ -1399,6 +1399,7 @@ find_shift_sequence (rtx read_reg,
{
enum machine_mode store_mode = GET_MODE (store_info->mem);
enum machine_mode read_mode = GET_MODE (read_info->mem);
rtx chosen_seq = NULL;
/* Some machines like the x86 have shift insns for each size of
operand. Other machines like the ppc or the ia-64 may only have
@ -1409,8 +1410,9 @@ find_shift_sequence (rtx read_reg,
for (; access_size < UNITS_PER_WORD; access_size *= 2)
{
rtx target, new_reg;
rtx target, new_reg, shift_seq, insn;
enum machine_mode new_mode;
int cost;
/* Try a wider mode if truncating the store mode to ACCESS_SIZE
bytes requires a real instruction. */
@ -1431,67 +1433,57 @@ find_shift_sequence (rtx read_reg,
target = expand_binop (new_mode, lshr_optab, new_reg,
GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
if (target == new_reg)
shift_seq = get_insns ();
end_sequence ();
if (target != new_reg || shift_seq == NULL)
continue;
cost = 0;
for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
if (INSN_P (insn))
cost += insn_rtx_cost (PATTERN (insn));
/* The computation up to here is essentially independent
of the arguments and could be precomputed. It may
not be worth doing so. We could precompute if
worthwhile or at least cache the results. The result
technically depends on SHIFT, ACCESS_SIZE, and
GET_MODE_CLASS (READ_MODE). But in practice the
answer will depend only on ACCESS_SIZE. */
if (cost > COSTS_N_INSNS (1))
continue;
/* We found an acceptable shift. Generate a move to
take the value from the store and put it into the
shift pseudo, then shift it, then generate another
move to put in into the target of the read. */
start_sequence ();
emit_move_insn (new_reg, gen_lowpart (new_mode, store_info->rhs));
emit_insn (shift_seq);
convert_move (read_reg, new_reg, 1);
if (dump_file)
{
rtx shift_seq = get_insns ();
end_sequence ();
/* If cost is too great, set target to NULL and
let the iteration happen. */
if (shift_seq != NULL)
{
int cost = 0;
rtx insn;
for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
if (INSN_P (insn))
cost += insn_rtx_cost (PATTERN (insn));
/* The computation up to here is essentially independent
of the arguments and could be precomputed. It may
not be worth doing so. We could precompute if
worthwhile or at least cache the results. The result
technically depends on SHIFT, ACCESS_SIZE, and
GET_MODE_CLASS (READ_MODE). But in practice the
answer will depend only on ACCESS_SIZE. */
if (cost <= COSTS_N_INSNS (1))
{
/* We found an acceptable shift. Generate a move to
take the value from the store and put it into the
shift pseudo, then shift it, then generate another
move to put in into the target of the read. */
start_sequence ();
emit_move_insn (new_reg, gen_lowpart (new_mode, store_info->rhs));
emit_insn (shift_seq);
convert_move (read_reg, new_reg, 1);
if (dump_file)
{
fprintf (dump_file, " -- adding extract insn r%d:%s = r%d:%s\n",
REGNO (new_reg), GET_MODE_NAME (new_mode),
REGNO (store_info->rhs), GET_MODE_NAME (store_mode));
fprintf (dump_file, " -- adding extract insn r%d:%s = r%d:%s\n",
REGNO (new_reg), GET_MODE_NAME (new_mode),
REGNO (store_info->rhs), GET_MODE_NAME (store_mode));
fprintf (dump_file, " -- with shift of r%d by %d\n",
REGNO(new_reg), shift);
fprintf (dump_file, " -- and second extract insn r%d:%s = r%d:%s\n",
REGNO (read_reg), GET_MODE_NAME (read_mode),
REGNO (new_reg), GET_MODE_NAME (new_mode));
}
/* Get the three insn sequence and return it. */
shift_seq = get_insns ();
end_sequence ();
return shift_seq;
}
}
fprintf (dump_file, " -- with shift of r%d by %d\n",
REGNO(new_reg), shift);
fprintf (dump_file, " -- and second extract insn r%d:%s = r%d:%s\n",
REGNO (read_reg), GET_MODE_NAME (read_mode),
REGNO (new_reg), GET_MODE_NAME (new_mode));
}
else
/* End the sequence. */
end_sequence ();
/* Get the three insn sequence and return it. */
chosen_seq = get_insns ();
end_sequence ();
break;
}
return NULL;
return chosen_seq;
}