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re PR tree-optimization/87665 (gcc HEAD (svn: 265340) breaks elements on resize)

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2018-10-24  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87665
	* tree-vect-data-refs.c (vect_preserves_scalar_order_p): Adjust
	to reflect reality.

	* gcc.dg/torture/pr87665.c: New testcase.

From-SVN: r265452
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Richard Biener 2018-10-24 06:52:45 +00:00 • committed by Richard Biener
parent 4b763deedb
commit bf32992748
4 changed files with 57 additions and 9 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2018-10-24 Richard Biener <rguenther@suse.de>
PR tree-optimization/87665
* tree-vect-data-refs.c (vect_preserves_scalar_order_p): Adjust
to reflect reality.
2018-10-12 Jeff Law <law@redhat.com>
* config/h8300/h8300.c (h8300_expand_prologue): Fix stm generation

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-10-24 Richard Biener <rguenther@suse.de>
PR tree-optimization/87665
* gcc.dg/torture/pr87665.c: New testcase.
2018-10-23 Jakub Jelinek <jakub@redhat.com>
* g++.dg/cpp2a/lambda-this3.C: Limit dg-bogus directives to c++17_down

27
gcc/testsuite/gcc.dg/torture/pr87665.c Normal file
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@ -0,0 +1,27 @@
/* { dg-do run } */
struct X { long x; long y; };
struct X a[1024], b[1024];
void foo ()
{
for (int i = 0; i < 1024; ++i)
{
long tem = a[i].x;
a[i].x = 0;
b[i].x = tem;
b[i].y = a[i].y;
}
}
int main()
{
for (int i = 0; i < 1024; ++i)
a[i].x = i;
foo ();
for (int i = 0; i < 1024; ++i)
if (b[i].x != i)
__builtin_abort();
return 0;
}

28
gcc/tree-vect-data-refs.c
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@ -210,16 +210,26 @@ vect_preserves_scalar_order_p (dr_vec_info *dr_info_a, dr_vec_info *dr_info_b)
return true;
/* STMT_A and STMT_B belong to overlapping groups. All loads in a
group are emitted at the position of the first scalar load and all
group are emitted at the position of the last scalar load and all
stores in a group are emitted at the position of the last scalar store.
Thus writes will happen no earlier than their current position
(but could happen later) while reads will happen no later than their
current position (but could happen earlier). Reordering is therefore
only possible if the first access is a write. */
stmtinfo_a = vect_orig_stmt (stmtinfo_a);
stmtinfo_b = vect_orig_stmt (stmtinfo_b);
stmt_vec_info earlier_stmt_info = get_earlier_stmt (stmtinfo_a, stmtinfo_b);
return !DR_IS_WRITE (STMT_VINFO_DATA_REF (earlier_stmt_info));
Compute that position and check whether the resulting order matches
the current one. */
stmt_vec_info last_a = DR_GROUP_FIRST_ELEMENT (stmtinfo_a);
if (last_a)
for (stmt_vec_info s = DR_GROUP_NEXT_ELEMENT (last_a); s;
s = DR_GROUP_NEXT_ELEMENT (s))
last_a = get_later_stmt (last_a, s);
else
last_a = stmtinfo_a;
stmt_vec_info last_b = DR_GROUP_FIRST_ELEMENT (stmtinfo_b);
if (last_b)
for (stmt_vec_info s = DR_GROUP_NEXT_ELEMENT (last_b); s;
s = DR_GROUP_NEXT_ELEMENT (s))
last_b = get_later_stmt (last_b, s);
else
last_b = stmtinfo_b;
return ((get_later_stmt (last_a, last_b) == last_a)
== (get_later_stmt (stmtinfo_a, stmtinfo_b) == stmtinfo_a));
}
/* A subroutine of vect_analyze_data_ref_dependence. Handle