re PR middle-end/54838 (ICE: in merge_latch_edges, at cfgloop.c:678 with -ftracer)

PR54838

From-SVN: r194060

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6ba71f10a137cdfe226934be040f16a5419a27dc..18c930cc4c4485ef8e902ca5e8d82422adf7687f 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2012-12-02  Marek Polacek  <polacek@redhat.com>
+
+       PR middle-end/54838
+       * cprop.c (bypass_block): Determine number of latches.  Return
+       when there is more than one latch edge.
+
 2012-12-02  Teresa Johnson  <tejohnson@google.com>
 
        PR gcov-profile/55551

diff --git a/gcc/cprop.c b/gcc/cprop.c
index 3fb266a2592680831b5685cbc800fa6c26833b31..ec896a46062dd706a8e5fb013602d80f4fe4ec41 100644 (file)
--- a/gcc/cprop.c
+++ b/gcc/cprop.c
@@ -1510,13 +1510,28 @@ bypass_block (basic_block bb, rtx setcc, rtx jump)
   if (note)
     find_used_regs (&XEXP (note, 0), NULL);
 
-  may_be_loop_header = false;
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    if (e->flags & EDGE_DFS_BACK)
-      {
-       may_be_loop_header = true;
-       break;
-      }
+  /* Determine whether there are more latch edges.  Threading through
+     a loop header with more than one latch is delicate, see e.g.
+     tree-ssa-threadupdate.c:thread_through_loop_header.  */
+  if (current_loops)
+    {
+      may_be_loop_header = bb == bb->loop_father->header;
+      if (may_be_loop_header
+         && bb->loop_father->latch == NULL)
+       return 0;
+    }
+  else
+    {
+      unsigned n_back_edges = 0;
+      FOR_EACH_EDGE (e, ei, bb->preds)
+       if (e->flags & EDGE_DFS_BACK)
+         n_back_edges++;
+
+      may_be_loop_header = n_back_edges > 0;
+
+      if (n_back_edges > 1)
+        return 0;
+    }
 
   change = 0;
   for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3103cf131f930c8572d5e2c694c2d7d75eb1af81..981d0d1c8e8d54f6a759046ad9392d9708fdd0ed 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2012-12-02  Marek Polacek  <polacek@redhat.com>
+
+       PR middle-end/54838
+       * gcc.dg/pr54838.c: New test.
+
 2012-12-01  Xinliang David Li  <davidxl@google.com>
 
        * gcc.target/i386/ifcvt-onecmpl-abs-1.c: Check for

diff --git a/gcc/testsuite/gcc.dg/pr54838.c b/gcc/testsuite/gcc.dg/pr54838.c
new file mode 100644 (file)
index 0000000..9ed92f9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr54838.c
@@ -0,0 +1,24 @@
+/* PR middle-end/54838 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-forward-propagate -ftracer" } */
+
+void bar (void);
+
+void
+foo (void *b, int *c)
+{
+again:
+  switch (*c)
+    {
+    case 1:
+      if (!b)
+       {
+         bar ();
+         return;
+       }
+      goto again;
+    case 3:
+      if (!b)
+       goto again;
+    }
+}