[patch] Add counter inits to zero_iter_bb in expand_omp_for_init_counts

[Tom de Vries]

Hi,

this patch adds initialization in zero_iter_bb of counters introduced in 
expand_omp_for_init_counts.

This removes the need to set TREE_NO_WARNING on those counters.

Build on x86_64 and reg-tested with gomp.exp and target-libgomp c.exp.

OK for trunk, if bootstrap and reg-test on x86_64 succeeds?

Thanks,
- Tom
Add counter inits to zero_iter_bb in expand_omp_for_init_counts

2015-10-01  Tom de Vries  <t...@codesourcery.com>

	* omp-low.c (expand_omp_for_init_counts): Add inits for counters in
	zero_iter_bb.
	(expand_omp_for_generic): Remove TREE_NO_WARNING setttings on counters.

	* gcc.dg/gomp/collapse-2.c: New test.
---
 gcc/omp-low.c                          | 26 +++++++++++++++++++-------
 gcc/testsuite/gcc.dg/gomp/collapse-2.c | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/gomp/collapse-2.c

diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 8bcad08..8181757 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -5732,6 +5732,7 @@ expand_omp_for_init_counts (struct omp_for_data *fd, gimple_stmt_iterator *gsi,
       return;
     }
 
+  bool created_zero_iter_bb = false;
   for (i = 0; i < fd->collapse; i++)
     {
       tree itype = TREE_TYPE (fd->loops[i].v);
@@ -5774,6 +5775,7 @@ expand_omp_for_init_counts (struct omp_for_data *fd, gimple_stmt_iterator *gsi,
 	      gsi_insert_before (gsi, assign_stmt, GSI_SAME_STMT);
 	      set_immediate_dominator (CDI_DOMINATORS, zero_iter_bb,
 				       entry_bb);
+	      created_zero_iter_bb = true;
 	    }
 	  ne = make_edge (entry_bb, zero_iter_bb, EDGE_FALSE_VALUE);
 	  ne->probability = REG_BR_PROB_BASE / 2000 - 1;
@@ -5826,6 +5828,23 @@ expand_omp_for_init_counts (struct omp_for_data *fd, gimple_stmt_iterator *gsi,
 	  expand_omp_build_assign (gsi, fd->loop.n2, t);
 	}
     }
+
+  if (created_zero_iter_bb)
+    {
+      gimple_stmt_iterator gsi = gsi_after_labels (zero_iter_bb);
+      /* Atm counts[0] doesn't seem to be used beyond create_zero_iter_bb,
+	 but for robustness-sake we include that one as well.  */
+      for (i = 0; i < fd->collapse; i++)
+	{
+	  tree var = counts[i];
+	  if (!SSA_VAR_P (var))
+	    continue;
+
+	  tree zero = build_zero_cst (type);
+	  gassign *assign_stmt = gimple_build_assign (var, zero);
+	  gsi_insert_before (&gsi, assign_stmt, GSI_SAME_STMT);
+	}
+    }
 }
 
 
@@ -6116,7 +6135,6 @@ expand_omp_for_generic (struct omp_region *region,
   bool broken_loop = region->cont == NULL;
   edge e, ne;
   tree *counts = NULL;
-  int i;
 
   gcc_assert (!broken_loop || !in_combined_parallel);
   gcc_assert (fd->iter_type == long_integer_type_node
@@ -6185,12 +6203,6 @@ expand_omp_for_generic (struct omp_region *region,
 
       if (zero_iter_bb)
 	{
-	  /* Some counts[i] vars might be uninitialized if
-	     some loop has zero iterations.  But the body shouldn't
-	     be executed in that case, so just avoid uninit warnings.  */
-	  for (i = first_zero_iter; i < fd->collapse; i++)
-	    if (SSA_VAR_P (counts[i]))
-	      TREE_NO_WARNING (counts[i]) = 1;
 	  gsi_prev (&gsi);
 	  e = split_block (entry_bb, gsi_stmt (gsi));
 	  entry_bb = e->dest;
diff --git a/gcc/testsuite/gcc.dg/gomp/collapse-2.c b/gcc/testsuite/gcc.dg/gomp/collapse-2.c
new file mode 100644
index 0000000..5319f89
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/gomp/collapse-2.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fopenmp -fdump-tree-ssa" } */
+
+#define N 100
+
+int a[N][N];
+
+void
+foo (int m, int n)
+{
+  int i, j;
+#pragma omp parallel
+#pragma omp for collapse(2) schedule (runtime)
+  for (i = 0; i < m; i++)
+    for (j = 0; j < n; j++)
+      a[i][j] = 1;
+}
+
+/* { dg-final { scan-tree-dump-not "(?n)PHI.*count.*\\(D\\)" "ssa" } } */
-- 
1.9.1