Re: [PATCH, PR69110] Don't return NULL access_fns in dr_analyze_indices

[Tom de Vries <Tom_deVries@mentor.com>]

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On 12/01/16 14:04, Richard Biener wrote:
> On Tue, 12 Jan 2016, Tom de Vries wrote:
>
>> On 12/01/16 12:22, Richard Biener wrote:
>>> Doesnt' the same issue apply to
>>>
>>>>> unsigned int *p;
>>>>>
>>>>> static void __attribute__((noinline, noclone))
>>>>> foo (void)
>>>>> {
>>>>>    unsigned int z;
>>>>>
>>>>>    for (z = 0; z < N; ++z)
>>>>>      ++(*p);
>>>>> }
>>> thus when we have a MEM_REF[p_1]?  SCEV will not analyze
>>> its evolution to a POLYNOMIAL_CHREC and thus access_fns will
>>> be NULL again.
>>>
>>
>> I didn't manage to trigger this scenario, though I could probably make it
>> happen by modifying ftree-loop-im to work in one case (the load of the value
>> of p) but not the other (the *p load and store).
>>
>>> I think avoiding a NULL access_fns is ok but it should be done
>>> unconditionally, not only for the DECL_P case.
>>
>> Ok, I'll retest and commit this patch.
>
> Please add a comment as well.

Patch updated with comment.

During testing however, I ran into two testsuite regressions:

1.

-PASS: gfortran.dg/graphite/pr39516.f   -O  (test for excess errors)
+FAIL: gfortran.dg/graphite/pr39516.f   -O  (internal compiler error)
+FAIL: gfortran.dg/graphite/pr39516.f   -O  (test for excess errors)

AFAIU, this is a duplicate of PR68976.

Should I wait with committing the patch until PR68976 is fixed?

2.

-XFAIL: gcc.dg/graphite/scop-pr66980.c scan-tree-dump-times graphite 
"number of SCoPs: 1" 1
+XPASS: gcc.dg/graphite/scop-pr66980.c scan-tree-dump-times graphite 
"number of SCoPs: 1" 1

AFAIU, this is not a real regression, but the testcase needs to be 
updated. I'm not sure how. Sebastian, perhaps you have an idea there?

Thanks,
- Tom


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From 24dfdb5a8a536203ad159bcbeaee6931be032f32 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tom@codesourcery.com>
Date: Tue, 12 Jan 2016 01:45:11 +0100
Subject: [PATCH] Don't return NULL access_fns in dr_analyze_indices

2016-01-12  Tom de Vries  <tom@codesourcery.com>

	* tree-data-ref.c (dr_analyze_indices): Don't return NULL access_fns.

	* gcc.dg/autopar/pr69110.c: New test.

	* testsuite/libgomp.c/pr69110.c: New test.
---
 gcc/testsuite/gcc.dg/autopar/pr69110.c | 19 +++++++++++++++++++
 gcc/tree-data-ref.c                    |  4 ++++
 libgomp/testsuite/libgomp.c/pr69110.c  | 26 ++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/autopar/pr69110.c
 create mode 100644 libgomp/testsuite/libgomp.c/pr69110.c

diff --git a/gcc/testsuite/gcc.dg/autopar/pr69110.c b/gcc/testsuite/gcc.dg/autopar/pr69110.c
new file mode 100644
index 0000000..e236015
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/autopar/pr69110.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -ftree-parallelize-loops=2 -fno-tree-loop-im -fdump-tree-parloops-details" } */
+
+#define N 1000
+
+unsigned int i = 0;
+
+void
+foo (void)
+{
+  unsigned int z;
+  for (z = 0; z < N; ++z)
+    ++i;
+}
+
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 0 "parloops" } } */
+/* { dg-final { scan-tree-dump-times "FAILED: data dependencies exist across iterations" 1 "parloops" } } */
+
+
diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index a40f40d..7ff5db7 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -1023,6 +1023,10 @@ dr_analyze_indices (struct data_reference *dr, loop_p nest, loop_p loop)
 		    build_int_cst (reference_alias_ptr_type (ref), 0));
     }
 
+  /* Ensure that DR_NUM_DIMENSIONS (dr) != 0.  */
+  if (access_fns == vNULL)
+    access_fns.safe_push (integer_zero_node);
+
   DR_BASE_OBJECT (dr) = ref;
   DR_ACCESS_FNS (dr) = access_fns;
 }
diff --git a/libgomp/testsuite/libgomp.c/pr69110.c b/libgomp/testsuite/libgomp.c/pr69110.c
new file mode 100644
index 0000000..0d9e5ca
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/pr69110.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+/* { dg-options "-ftree-parallelize-loops=2 -O1 -fno-tree-loop-im" } */
+
+#define N 1000
+
+unsigned int i = 0;
+
+static void __attribute__((noinline, noclone))
+foo (void)
+{
+  unsigned int z;
+  for (z = 0; z < N; ++z)
+    ++i;
+}
+
+extern void abort (void);
+
+int
+main (void)
+{
+  foo ();
+  if (i != N)
+    abort ();
+
+  return 0;
+}
-- 
1.9.1