From ec64ffc8501c20efdebefb494f3c90ab44199b60 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Wed, 14 Mar 2018 08:07:45 +0000
Subject: [PATCH] re PR tree-optimization/84830 (ICE in compute_antic, at
 tree-ssa-pre.c:2388)

2018-03-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/84830
	* tree-ssa-pre.c (compute_antic_aux): Intersect the new ANTIC_IN
	with the old one to avoid oscillations.

	* gcc.dg/torture/pr84830.c: New testcase.

From-SVN: r258514
---
 gcc/ChangeLog                          |  6 ++++
 gcc/testsuite/ChangeLog                |  5 +++
 gcc/testsuite/gcc.dg/torture/pr84830.c | 46 ++++++++++++++++++++++++++
 gcc/tree-ssa-pre.c                     | 29 ++++++++++++++++
 4 files changed, 86 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr84830.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5eaafcfb9bb..550e2b6b3e0 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-03-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/84830
+	* tree-ssa-pre.c (compute_antic_aux): Intersect the new ANTIC_IN
+	with the old one to avoid oscillations.
+
 2018-03-13  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR target/83712
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a4bf53c8bc4..0175d4342c0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/84830
+	* gcc.dg/torture/pr84830.c: New testcase.
+
 2018-03-14  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/84596
diff --git a/gcc/testsuite/gcc.dg/torture/pr84830.c b/gcc/testsuite/gcc.dg/torture/pr84830.c
new file mode 100644
index 00000000000..d076170d258
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr84830.c
@@ -0,0 +1,46 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fno-tree-ch -fno-tree-vrp" } */
+
+int x0;
+
+void
+br (int yp, int oo)
+{
+  int *qi = &yp;
+
+  if (oo == 0)
+    {
+g8:
+      if (x0 != 0)
+	x0 = yp;
+      else if (oo != 0)
+	x0 = yp;
+
+      if (x0 == 0)
+	{
+	  *qi = 0;
+	  x0 = *qi;
+	}
+
+      if (x0 != 0)
+	{
+	  ++oo;
+	  goto g8;
+	}
+
+      if (yp == oo)
+	yp += !!oo;
+    }
+  else
+    {
+      x0 = 1;
+      while (x0 < 2)
+	{
+	  qi = &oo;
+	  ++oo;
+	  x0 = 1;
+	}
+    }
+
+  goto g8;
+}
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index f165a1eb975..c3d2bbac957 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -2154,6 +2154,35 @@ compute_antic_aux (basic_block block, bool block_has_abnormal_pred_edge)
   /* clean (ANTIC_IN (block)) is defered to after the iteration converged
      because it can cause non-convergence, see for example PR81181.  */
 
+  /* Intersect ANTIC_IN with the old ANTIC_IN.  This is required until
+     we properly represent the maximum expression set, thus not prune
+     values without expressions during the iteration.  */
+  if (was_visited
+      && bitmap_and_into (&ANTIC_IN (block)->values, &old->values))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "warning: intersecting with old ANTIC_IN "
+		 "shrinks the set\n");
+      /* Prune expressions not in the value set.  */
+      bitmap_iterator bi;
+      unsigned int i;
+      unsigned int to_clear = -1U;
+      FOR_EACH_EXPR_ID_IN_SET (ANTIC_IN (block), i, bi)
+	{
+	  if (to_clear != -1U)
+	    {
+	      bitmap_clear_bit (&ANTIC_IN (block)->expressions, to_clear);
+	      to_clear = -1U;
+	    }
+	  pre_expr expr = expression_for_id (i);
+	  unsigned int value_id = get_expr_value_id (expr);
+	  if (!bitmap_bit_p (&ANTIC_IN (block)->values, value_id))
+	    to_clear = i;
+	}
+      if (to_clear != -1U)
+	bitmap_clear_bit (&ANTIC_IN (block)->expressions, to_clear);
+    }
+
   if (!bitmap_set_equal (old, ANTIC_IN (block)))
     {
       changed = true;