re PR tree-optimization/71433 (-Warray-bounds false positive with -O2)

2017-01-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71433
	* tree-vrp.c (register_new_assert_for): Merge same asserts
	on all incoming edges.
	(process_assert_insertions_for): Handle insertions at the
	beginning of BBs.

	* gcc.dg/Warray-bounds-20.c: New testcase.

From-SVN: r244520

gcc/ChangeLog

+2017-01-17  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/71433
+	* tree-vrp.c (register_new_assert_for): Merge same asserts
+	on all incoming edges.
+	(process_assert_insertions_for): Handle insertions at the
+	beginning of BBs.
+
 2017-01-17  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* config/i386/cygwin.h (LIBGCJ_SONAME): Remove.

gcc/testsuite/ChangeLog

 2017-01-17  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71433
+	* gcc.dg/Warray-bounds-20.c: New testcase.
+
+2017-01-17  Richard Biener  <rguenther@suse.de>
+
 	PR testsuite/52563
 	PR testsuite/71237
 	PR testsuite/77737

gcc/testsuite/gcc.dg/Warray-bounds-20.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -Warray-bounds" } */
+
+int t[1];
+int fct (int r, long e)
+{
+  int d = 0;
+  if (r == 4)
+    r = 1;
+  if (e < -52)
+    d = r == 0 ? 1 : 2;
+  else
+    {
+      int i, n = 53;
+      if (__builtin_expect (e < 0, 0))
+	n += e;
+      for (i = 1 ; i < n / 64 + 1 ; i++)
+	t[i] = 0; /* { dg-bogus "array bounds" } */
+    }
+  return d;
+}

gcc/tree-vrp.c

@@ -5032,6 +5032,17 @@ register_new_assert_for (tree name, tree expr,
 	      loc->si = si;
 	      return;
 	    }
+	  /* If we have the same assertion on all incoming edges of a BB
+	     instead insert it at the beginning of it.  */
+	  if (e && loc->e
+	      && dest_bb == loc->e->dest
+	      && EDGE_COUNT (dest_bb->preds) == 2)
+	    {
+	      loc->bb = dest_bb;
+	      loc->e = NULL;
+	      loc->si = gsi_none ();
+	      return;
+	    }
 	}
 
       /* Update the last node of the list and move to the next one.  */
@@ -6429,6 +6440,15 @@ process_assert_insertions_for (tree name, assert_locus *loc)
       return true;
     }
 
+  /* If the stmt iterator points at the end then this is an insertion
+     at the beginning of a block.  */
+  if (gsi_end_p (loc->si))
+    {
+      gimple_stmt_iterator si = gsi_after_labels (loc->bb);
+      gsi_insert_before (&si, assert_stmt, GSI_SAME_STMT);
+      return false;
+
+    }
   /* Otherwise, we can insert right after LOC->SI iff the
      statement must not be the last statement in the block.  */
   stmt = gsi_stmt (loc->si);