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re PR tree-optimization/79663 (r244815 causes 10% regression for spec1k/172.mgrid on AArch64)

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2017-01-21  Bin Cheng  <bin.cheng@arm.com>

	PR tree-optimization/79663
	* tree-predcom.c (combine_chains): Process refs in reverse order
	only for ZERO length chains, and add explaining comment.

From-SVN: r245689
This commit is contained in:
Bin Cheng 2017-02-23 22:02:01 +00:00 committed by Jeff Law
parent 06b909b07e
commit d822f3d585
2 changed files with 35 additions and 24 deletions
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gcc/ChangeLog
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@ -1,3 +1,9 @@
2017-02-23 Bin Cheng <bin.cheng@arm.com>
PR tree-optimization/79663
* tree-predcom.c (combine_chains): Process refs in reverse order
only for ZERO length chains, and add explaining comment.
2017-02-23 Jeff Law <law@redhat.com>
PR tree-optimization/79578

53
gcc/tree-predcom.c
View File

@ -2283,7 +2283,7 @@ combine_chains (chain_p ch1, chain_p ch2)
enum tree_code op = ERROR_MARK;
bool swap = false;
chain_p new_chain;
unsigned i;
int i, j, num;
gimple *root_stmt;
tree rslt_type = NULL_TREE;
@ -2305,6 +2305,9 @@ combine_chains (chain_p ch1, chain_p ch2)
return NULL;
}
ch1->combined = true;
ch2->combined = true;
if (swap)
std::swap (ch1, ch2);
@ -2317,39 +2320,41 @@ combine_chains (chain_p ch1, chain_p ch2)
new_chain->length = ch1->length;
gimple *insert = NULL;
auto_vec<dref> tmp_refs;
gcc_assert (ch1->refs.length () == ch2->refs.length ());
/* Process in reverse order so dominance point is ready when it comes
to the root ref. */
for (i = ch1->refs.length (); i > 0; i--)
num = ch1->refs.length ();
i = (new_chain->length == 0) ? num - 1 : 0;
j = (new_chain->length == 0) ? -1 : 1;
/* For ZERO length chain, process refs in reverse order so that dominant
position is ready when it comes to the root ref.
For non-ZERO length chain, process refs in order. See PR79663. */
for (; num > 0; num--, i += j)
{
r1 = ch1->refs[i - 1];
r2 = ch2->refs[i - 1];
r1 = ch1->refs[i];
r2 = ch2->refs[i];
nw = XCNEW (struct dref_d);
nw->distance = r1->distance;
nw->stmt = stmt_combining_refs (r1, r2, i == 1 ? insert : NULL);
/* Record dominance point where root combined stmt should be inserted
for chains with 0 length. Though all root refs dominate following
refs, it's possible the combined stmt doesn't. See PR70754. */
if (ch1->length == 0
/* For ZERO length chain, insert combined stmt of root ref at dominant
position. */
nw->stmt = stmt_combining_refs (r1, r2, i == 0 ? insert : NULL);
/* For ZERO length chain, record dominant position where combined stmt
of root ref should be inserted. In this case, though all root refs
dominate following ones, it's possible that combined stmt doesn't.
See PR70754. */
if (new_chain->length == 0
&& (insert == NULL || stmt_dominates_stmt_p (nw->stmt, insert)))
insert = nw->stmt;
tmp_refs.safe_push (nw);
new_chain->refs.safe_push (nw);
}
/* Restore the order for new chain's refs. */
for (i = tmp_refs.length (); i > 0; i--)
new_chain->refs.safe_push (tmp_refs[i - 1]);
ch1->combined = true;
ch2->combined = true;
/* For chains with 0 length, has_max_use_after must be true since root
combined stmt must dominates others. */
if (new_chain->length == 0)
{
/* Restore the order for ZERO length chain's refs. */
num = new_chain->refs.length () >> 1;
for (i = 0, j = new_chain->refs.length () - 1; i < num; i++, j--)
std::swap (new_chain->refs[i], new_chain->refs[j]);
/* For ZERO length chain, has_max_use_after must be true since root
combined stmt must dominates others. */
new_chain->has_max_use_after = true;
return new_chain;
}