[PATCH, PR68460] Always call free_stmt_vec_info_vec in gather_scalar_reductions

[Tom de Vries <Tom_deVries at mentor dot com>]

[ was: Re: [PATCH] Fix parloops gimple_uid usage ]

On 09/10/15 23:09, Tom de Vries wrote:
> @@ -2392,6 +2397,9 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
>     loop_vec_info simple_inner_loop_info = NULL;
>     bool allow_double_reduc = true;
>
> +  if (!stmt_vec_info_vec.exists ())
> +    init_stmt_vec_info_vec ();
> +
>     simple_loop_info = vect_analyze_loop_form (loop);
>     if (simple_loop_info == NULL)
>       return;
> @@ -2453,9 +2461,16 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
>     destroy_loop_vec_info (simple_loop_info, true);
>     destroy_loop_vec_info (simple_inner_loop_info, true);
>
> +  /* Release the claim on gimple_uid.  */
> +  free_stmt_vec_info_vec ();
> +

With the src/libgomp/testsuite/libgomp.c/pr46886.c testcase, compiled in 
addition with -ftree-vectorize, I ran into an ICE:
...
src/libgomp/testsuite/libgomp.c/pr46886.c:8:5: internal compiler error: 
in init_stmt_vec_info_vec, at tree-vect-stmts.c:8250
 int foo (void)
     ^~~

0x1196082 init_stmt_vec_info_vec()
	src/gcc/tree-vect-stmts.c:8250
0x11c3ed4 vectorize_loops()
	src/gcc/tree-vectorizer.c:510
0x10a7ea5 execute
	src/gcc/tree-ssa-loop.c:276
...

The ICE is caused by the fact that init_stmt_vec_info_vec is called at 
the start of vectorize_loops, while stmt_vec_info_vec is not empty. I 
traced this back to gather_scalar_reduction, where we call 
init_stmt_vec_info_vec, but we skip free_stmt_vec_info_vec if we take 
the early-out for simple_loop_info == NULL.

This patch fixes the ICE by making sure we always call 
free_stmt_vec_info_vec in gather_scalar_reduction.

Passes cc1/f951 rebuild and autopar testing.

OK for stage3 trunk if bootstrap and regtest succeeds?

Thanks,
- Tom

Always call free_stmt_vec_info_vec in gather_scalar_reductions

2015-11-20  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/68460
	* tree-parloops.c (gather_scalar_reductions): Also call
	free_stmt_vec_info_vec if simple_loop_info == NULL.

	* gcc.dg/autopar/pr68460.c: New test.

---
 gcc/testsuite/gcc.dg/autopar/pr68460.c | 35 ++++++++++++++++++++++++++++++++++
 gcc/tree-parloops.c                    |  6 +++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/autopar/pr68460.c b/gcc/testsuite/gcc.dg/autopar/pr68460.c
new file mode 100644
index 0000000..0c00065
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/autopar/pr68460.c
@@ -0,0 +1,35 @@
+/* { dg-do "compile" } */
+/* { dg-options "-O -ftree-parallelize-loops=2 -ftree-vectorize -fno-tree-ch -fno-tree-dominator-opts" } */
+
+void abort (void);
+
+int d[1024], e[1024];
+
+int
+foo (void)
+{
+  int s = 0;
+  int i;
+
+  for (i = 0; i < 1024; i++)
+    s += d[i] - e[i];
+
+  return s;
+}
+
+int
+main ()
+{
+  int i;
+
+  for (i = 0; i < 1024; i++)
+    {
+      d[i] = i * 2;
+      e[i] = i;
+    }
+
+  if (foo () != 1023 * 1024 / 2)
+    abort ();
+
+  return 0;
+}
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c
index 8d7912d..85cc78d 100644
--- a/gcc/tree-parloops.c
+++ b/gcc/tree-parloops.c
@@ -2433,7 +2433,7 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
 
   simple_loop_info = vect_analyze_loop_form (loop);
   if (simple_loop_info == NULL)
-    return;
+    goto gather_done;
 
   for (gsi = gsi_start_phis (loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
     {
@@ -2492,9 +2492,13 @@ gather_scalar_reductions (loop_p loop, reduction_info_table_type *reduction_list
   destroy_loop_vec_info (simple_loop_info, true);
   destroy_loop_vec_info (simple_inner_loop_info, true);
 
+ gather_done:
   /* Release the claim on gimple_uid.  */
   free_stmt_vec_info_vec ();
 
+  if (reduction_list->elements () == 0)
+    return;
+
   /* As gimple_uid is used by the vectorizer in between vect_analyze_loop_form
      and free_stmt_vec_info_vec, we can set gimple_uid of reduc_phi stmts only
      now.  */