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Delay swapping data refs in prune_runtime_alias_test_list

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prune_runtime_alias_test_list swapped dr_as between two dr_with_seg_len
pairs before finally deciding whether to merge them.  Bailing out later
would therefore leave the pairs in an incorrect state.

IMO a better fix would be to split this out into a subroutine that
produces a temporary dr_with_seg_len on success, rather than changing
an existing one in-place.  It would then be easy to merge both the dr_as
and dr_bs if we wanted to, rather than requiring one of them to be equal.
But here I tried to do something that could be backported if necessary.

2019-11-16  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-data-ref.c (prune_runtime_alias_test_list): Delay
	swapping the dr_as based on init values until we've decided
	whether to merge them.

From-SVN: r278349
This commit is contained in:
Richard Sandiford 2019-11-16 11:35:56 +00:00 • committed by Richard Sandiford
parent 1fb2b0f69e
commit 97602450b0
2 changed files with 21 additions and 9 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2019-11-16 Richard Sandiford <richard.sandiford@arm.com>
* tree-data-ref.c (prune_runtime_alias_test_list): Delay
swapping the dr_as based on init values until we've decided
whether to merge them.
2019-11-16 Richard Sandiford <richard.sandiford@arm.com>
* tree-data-ref.c (prune_runtime_alias_test_list): Sort the

24
gcc/tree-data-ref.c
View file

@ -1555,13 +1555,6 @@ prune_runtime_alias_test_list (vec<dr_with_seg_len_pair_t> *alias_pairs,
if (!ordered_p (init_a1, init_a2))
continue;
/* Make sure dr_a1 starts left of dr_a2. */
if (maybe_gt (init_a1, init_a2))
{
std::swap (*dr_a1, *dr_a2);
std::swap (init_a1, init_a2);
}
/* Work out what the segment length would be if we did combine
DR_A1 and DR_A2:
@ -1578,7 +1571,10 @@ prune_runtime_alias_test_list (vec<dr_with_seg_len_pair_t> *alias_pairs,
The lengths both have sizetype, so the sign is taken from
the step instead. */
if (!operand_equal_p (dr_a1->seg_len, dr_a2->seg_len, 0))
poly_uint64 new_seg_len = 0;
bool new_seg_len_p = !operand_equal_p (dr_a1->seg_len,
dr_a2->seg_len, 0);
if (new_seg_len_p)
{
poly_uint64 seg_len_a1, seg_len_a2;
if (!poly_int_tree_p (dr_a1->seg_len, &seg_len_a1)
@ -1596,14 +1592,24 @@ prune_runtime_alias_test_list (vec<dr_with_seg_len_pair_t> *alias_pairs,
int sign_a = tree_int_cst_sgn (indicator_a);
int sign_b = tree_int_cst_sgn (indicator_b);
poly_uint64 new_seg_len;
if (sign_a <= 0 && sign_b <= 0)
new_seg_len = lower_bound (seg_len_a1, seg_len_a2);
else if (sign_a >= 0 && sign_b >= 0)
new_seg_len = upper_bound (seg_len_a1, seg_len_a2);
else
continue;
}
/* At this point we're committed to merging the refs. */
/* Make sure dr_a1 starts left of dr_a2. */
if (maybe_gt (init_a1, init_a2))
{
std::swap (*dr_a1, *dr_a2);
std::swap (init_a1, init_a2);
}
if (new_seg_len_p)
{
dr_a1->seg_len = build_int_cst (TREE_TYPE (dr_a1->seg_len),
new_seg_len);
dr_a1->align = MIN (dr_a1->align, known_alignment (new_seg_len));