<a...@codesourcery.com> writes:
> Given a pattern with a number of operands:
>
> (match_operand 0 "" "=&v")
> (match_operand 1 "" " v0")
> (match_operand 2 "" " v0")
> (match_operand 3 "" " v0")
>
> GCC will currently increment "reject" once, for operand 0, and then decrement
> it once for each of the other operands, ending with reject == -2 and an
> assertion failure. If there's a conflict then it might try to decrement
> reject
> yet again.
>
> Incidentally, what these patterns are trying to achieve is an allocation in
> which operand 0 may match one of the other operands, but may not partially
> overlap any of them. Ideally there'd be a better way to do this.
>
> In any case, it will affect any pattern in which multiple operands may (or
> must) match an early-clobber operand.
>
> The patch only allows a reject-- when one has not already occurred, for that
> operand.
>
> 2018-09-05 Andrew Stubbs <a...@codesourcery.com>
>
> gcc/
> * lra-constraints.c (process_alt_operands): Check
> matching_early_clobber before decrementing reject, and set
> matching_early_clobber after.
> * lra-int.h (struct lra_operand_data): Add matching_early_clobber.
> * lra.c (setup_operand_alternative): Initialize matching_early_clobber.
> ---
> gcc/lra-constraints.c | 22 ++++++++++++++--------
> gcc/lra-int.h | 3 +++
> gcc/lra.c | 1 +
> 3 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
> index 8be4d46..55163f1 100644
> --- a/gcc/lra-constraints.c
> +++ b/gcc/lra-constraints.c
> @@ -2202,7 +2202,13 @@ process_alt_operands (int only_alternative)
> " %d Matching earlyclobber alt:"
> " reject--\n",
> nop);
> - reject--;
> + if (!curr_static_id->operand[m]
> + .matching_early_clobber)
> + {
> + reject--;
> + curr_static_id->operand[m]
> + .matching_early_clobber = 1;
> + }
> }
> /* Otherwise we prefer no matching
> alternatives because it gives more freedom
> @@ -2948,15 +2954,11 @@ process_alt_operands (int only_alternative)
> curr_alt_dont_inherit_ops[curr_alt_dont_inherit_ops_num++]
> = last_conflict_j;
> losers++;
> - /* Early clobber was already reflected in REJECT. */
> - lra_assert (reject > 0);
> if (lra_dump_file != NULL)
> fprintf
> (lra_dump_file,
> " %d Conflict early clobber reload: reject--\n",
> i);
> - reject--;
> - overall += LRA_LOSER_COST_FACTOR - 1;
> }
> else
> {
> @@ -2980,17 +2982,21 @@ process_alt_operands (int only_alternative)
> }
> curr_alt_win[i] = curr_alt_match_win[i] = false;
> losers++;
> - /* Early clobber was already reflected in REJECT. */
> - lra_assert (reject > 0);
> if (lra_dump_file != NULL)
> fprintf
> (lra_dump_file,
> " %d Matched conflict early clobber reloads: "
> "reject--\n",
> i);
> + }
> + /* Early clobber was already reflected in REJECT. */
> + if (!curr_static_id->operand[i].matching_early_clobber)
> + {
> + lra_assert (reject > 0);
> reject--;
> - overall += LRA_LOSER_COST_FACTOR - 1;
> + curr_static_id->operand[i].matching_early_clobber = 1;
> }
> + overall += LRA_LOSER_COST_FACTOR - 1;
> }
> if (lra_dump_file != NULL)
> fprintf (lra_dump_file, "
> alt=%d,overall=%d,losers=%d,rld_nregs=%d\n",
The idea looks good to me FWIW, but you can't use curr_static_id for
the state, since that's a static description of the .md pattern rather
than data about this particular instance.
Thanks,
Richard
