diff mbox

[PR69110] Don't return NULL access_fns in dr_analyze_indices

Message ID 5694F5BA.7030207@mentor.com
State New
Headers show

Commit Message

Tom de Vries Jan. 12, 2016, 12:46 p.m. UTC 
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.

Thanks,
- Tom

Comments

Richard Biener Jan. 12, 2016, 1:04 p.m. UTC | #1 
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.

> Thanks,
> - Tom
>
diff mbox

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                    |  3 +++
 libgomp/testsuite/libgomp.c/pr69110.c  | 26 ++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)

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..6503012 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -1023,6 +1023,9 @@  dr_analyze_indices (struct data_reference *dr, loop_p nest, loop_p loop)
 		    build_int_cst (reference_alias_ptr_type (ref), 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;
+}