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Tighten early exit in vect_analyze_data_ref_dependence (PR85586)

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The problem in this PR was that we didn't consider aliases between
writes in the same strided group.  After tightening the early exit
we get the expected abs(step) >= 2 versioning check.

2018-05-02  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/85586
	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Only
	exit early for statements in the same group if the accesses are
	not strided.

gcc/testsuite/
	PR tree-optimization/85586
	* gcc.dg/vect/pr85586.c: New test.

From-SVN: r259822
This commit is contained in:
Richard Sandiford 2018-05-02 07:40:22 +00:00 committed by Richard Sandiford
parent c2e1580cbe
commit 9e4da9b5d5
4 changed files with 59 additions and 2 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2018-05-02 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/85586
* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Only
exit early for statements in the same group if the accesses are
not strided.
2018-05-02 Tom de Vries <tom@codesourcery.com>
PR lto/85451

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-05-02 Richard Sandiford <richard.sandiford@linaro.org>
PR tree-optimization/85586
* gcc.dg/vect/pr85586.c: New test.
2018-05-01 Marc Glisse <marc.glisse@inria.fr>
PR tree-optimization/85143

43
gcc/testsuite/gcc.dg/vect/pr85586.c Normal file
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@ -0,0 +1,43 @@
#define N 100
void __attribute__ ((noipa))
foo (int *out, int *in, int step)
{
for (int i = 0; i < N; ++i)
{
out[0] = in[i];
out[1] = 2;
out += step;
}
}
int in[N];
int out[N * 2];
int
main (void)
{
for (int i = 0; i < N; ++i)
{
in[i] = i * (i + 1);
asm volatile ("" ::: "memory");
}
foo (out, in, 1);
for (int i = 0; i < N; ++i)
if (out[i] != in[i])
__builtin_abort ();
if (out[N] != 2)
__builtin_abort ();
foo (out + N - 1, in, -1);
if (out[0] != in[N - 1])
__builtin_abort ();
for (int i = 1; i <= N; ++i)
if (out[i] != 2)
__builtin_abort ();
return 0;
}
/* { dg-final { scan-tree-dump-times "LOOP VECTORIZED" 1 "vect" { target vect_int } } } */

6
gcc/tree-vect-data-refs.c
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@ -305,9 +305,11 @@ vect_analyze_data_ref_dependence (struct data_dependence_relation *ddr,
return false;
/* We do not have to consider dependences between accesses that belong
to the same group. */
to the same group, unless the stride could be smaller than the
group size. */
if (GROUP_FIRST_ELEMENT (stmtinfo_a)
&& GROUP_FIRST_ELEMENT (stmtinfo_a) == GROUP_FIRST_ELEMENT (stmtinfo_b))
&& GROUP_FIRST_ELEMENT (stmtinfo_a) == GROUP_FIRST_ELEMENT (stmtinfo_b)
&& !STMT_VINFO_STRIDED_P (stmtinfo_a))
return false;
/* Even if we have an anti-dependence then, as the vectorized loop covers at