Re: [PATCH] Handle empty infinite loops in OpenACC for PR84955

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

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On 04/12/2018 08:58 PM, Jakub Jelinek wrote:
> On Thu, Apr 12, 2018 at 11:39:43AM -0700, Cesar Philippidis wrote:
>> Strange. I didn't observe any regressions when I tested it. But, then
>> again, I was testing against revision
>>
>> r259092 | jason | 2018-04-04 09:42:55 -0700 (Wed, 04 Apr 2018) | 4 lines
>>
>> which is over a week old. I'll revert that patch for now, and revisit
>> this issue in stage1.
> 
> You should have kept the omp-expand.c chunk, that is correct and shouldn't
> cause issues.

Committed as attached (with correct changelog entry, the previously 
committed patch had an incorrect one).

I've filed the lto ICE (described as "the second problem" in this 
thread) as PR85422 - "[openacc] ICE at cfgloop.c:468: segfault in 
flow_loops_find".

[ When changing dg-do compile to link in the test-cases in this patch, 
we run into PR85422, which shows that in the reverted patch the 
problematic fix was actually not exercised by the test-cases. ]

Thanks,
- Tom

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[openacc] Fix ICE when compiling tile loop containing infinite loop

2018-04-16  Cesar Philippidis  <cesar@codesourcery.com>
	    Tom de Vries  <tom@codesourcery.com>

	PR middle-end/84955
	* omp-expand.c (expand_oacc_for): Add dummy false branch for
	tiled basic blocks without omp continue statements.

	* testsuite/libgomp.oacc-c-c++-common/pr84955.c: New test.
	* testsuite/libgomp.oacc-fortran/pr84955.f90: New test.

---
 gcc/omp-expand.c                                      |  8 ++++++++
 libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955.c | 15 +++++++++++++++
 libgomp/testsuite/libgomp.oacc-fortran/pr84955.f90    | 13 +++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/gcc/omp-expand.c b/gcc/omp-expand.c
index bb20490..c7d30ea 100644
--- a/gcc/omp-expand.c
+++ b/gcc/omp-expand.c
@@ -5439,6 +5439,14 @@ expand_oacc_for (struct omp_region *region, struct omp_for_data *fd)
 
 	  split->flags ^= EDGE_FALLTHRU | EDGE_TRUE_VALUE;
 
+	  /* Add a dummy exit for the tiled block when cont_bb is missing.  */
+	  if (cont_bb == NULL)
+	    {
+	      edge e = make_edge (body_bb, exit_bb, EDGE_FALSE_VALUE);
+	      e->probability = profile_probability::even ();
+	      split->probability = profile_probability::even ();
+	    }
+
 	  /* Initialize the user's loop vars.  */
 	  gsi = gsi_start_bb (elem_body_bb);
 	  expand_oacc_collapse_vars (fd, true, &gsi, counts, e_offset);
diff --git a/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955.c b/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955.c
new file mode 100644
index 0000000..e528faa
--- /dev/null
+++ b/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955.c
@@ -0,0 +1,15 @@
+/* { dg-do compile }  */
+
+int
+main (void)
+{
+  int i, j;
+
+#pragma acc parallel loop tile(2,3)
+  for (i = 1; i < 10; i++)
+    for (j = 1; j < 10; j++)
+      for (;;)
+	;
+
+  return i + j;
+}
diff --git a/libgomp/testsuite/libgomp.oacc-fortran/pr84955.f90 b/libgomp/testsuite/libgomp.oacc-fortran/pr84955.f90
new file mode 100644
index 0000000..dc85865
--- /dev/null
+++ b/libgomp/testsuite/libgomp.oacc-fortran/pr84955.f90
@@ -0,0 +1,13 @@
+! { dg-do compile }
+
+subroutine s
+   integer :: i, j
+   !$acc parallel loop tile(2,3)
+   do i = 1, 10
+      do j = 1, 10
+         do
+         end do
+      end do
+   end do
+  !$acc end parallel loop
+end subroutine s