From: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 1 Aug 2017 13:36:50 +0000 (+0000)
Subject: 2017-08-01  Richard Biener  <rguenther@suse.de>
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4bd03d5ccf6aa0d5778dc2204ef8b671546938a3;p=thirdparty%2Fgcc.git

2017-08-01  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/81181
	* tree-ssa-pre.c (compute_antic_aux): Defer clean() to ...
	(compute_antic): ... end of iteration here.

	* gcc.dg/torture/pr81181.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@250777 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d5fc875705e0..83f9b49ba2c3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2017-08-01  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81181
+	* tree-ssa-pre.c (compute_antic_aux): Defer clean() to ...
+	(compute_antic): ... end of iteration here.
+
 2017-08-01  James Greenhalgh  <james.greenhalgh@arm.com>
 
 	* common.opt (ftree-vectorize): No longer set flag_tree_vectorize.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c25f0210eb46..768321d4215c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-01  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81181
+	* gcc.dg/torture/pr81181.c: New testcase.
+
 2017-08-01  Martin Liska  <mliska@suse.cz>
 
 	PR middle-end/70140
diff --git a/gcc/testsuite/gcc.dg/torture/pr81181.c b/gcc/testsuite/gcc.dg/torture/pr81181.c
new file mode 100644
index 000000000000..e7216d7bf3e0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr81181.c
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+
+unsigned int lh;
+
+void
+ny (int t3, int ys, int rt, int p8)
+{
+  if (lh != 0)
+    {
+      if (0)
+	{
+oo:
+	  do
+	    {
+	      rt = (p8 != 0) ? t3 : 0;
+	      rt = (rt != 0 || lh != (unsigned int)ys);
+	      rt += lh + ys;
+	    }
+	  while (t3 <= 0);
+
+	  lh = ys;
+	  ys = rt;
+	}
+
+      if (lh != 0)
+	p8 = lh;
+    }
+
+  goto oo;
+}
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index eaadaad5db35..afe898bea9db 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -2120,7 +2120,8 @@ static sbitmap has_abnormal_preds;
      ANTIC_OUT[BLOCK] = phi_translate (ANTIC_IN[succ(BLOCK)])
 
    ANTIC_IN[BLOCK] = clean(ANTIC_OUT[BLOCK] U EXP_GEN[BLOCK] - TMP_GEN[BLOCK])
-*/
+
+   Note that clean() is deferred until after the iteration.  */
 
 static bool
 compute_antic_aux (basic_block block, bool block_has_abnormal_pred_edge)
@@ -2220,7 +2221,8 @@ compute_antic_aux (basic_block block, bool block_has_abnormal_pred_edge)
     bitmap_value_insert_into_set (ANTIC_IN (block),
 				  expression_for_id (bii));
 
-  clean (ANTIC_IN (block));
+  /* clean (ANTIC_IN (block)) is defered to after the iteration converged
+     because it can cause non-convergence, see for example PR81181.  */
 
   if (!was_visited || !bitmap_set_equal (old, ANTIC_IN (block)))
     changed = true;
@@ -2456,6 +2458,12 @@ compute_antic (void)
       gcc_checking_assert (num_iterations < 500);
     }
 
+  /* We have to clean after the dataflow problem converged as cleaning
+     can cause non-convergence because it is based on expressions
+     rather than values.  */
+  FOR_EACH_BB_FN (block, cfun)
+    clean (ANTIC_IN (block));
+
   statistics_histogram_event (cfun, "compute_antic iterations",
 			      num_iterations);