The code mistakenly thinks any cond_jump has two successors.  This is
not true if both destinations are the same, as can happen with weird
patterns as in the PR.

Bootstrapped and tested on powerpc64-linux; also tested the simplified
test in the PR on an x86_64-linux cross.

Sorry for the breakage.  Is this okay for trunk?


Segher


2015-11-09  Segher Boessenkool  <seg...@kernel.crashing.org>

        * gcc/bb-reorder.c (reorder_basic_blocks_simple): Treat a conditional
        branch with only one successor just like unconditional branches.

---
 gcc/bb-reorder.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gcc/bb-reorder.c b/gcc/bb-reorder.c
index 5f1c2cc..950b1a1 100644
--- a/gcc/bb-reorder.c
+++ b/gcc/bb-reorder.c
@@ -2304,7 +2304,9 @@ reorder_basic_blocks_simple (void)
       if (JUMP_P (end) && extract_asm_operands (end))
        continue;
 
-      if (any_condjump_p (end))
+      if (single_succ_p (bb))
+       edges[n++] = EDGE_SUCC (bb, 0);
+      else if (any_condjump_p (end))
        {
          edge e0 = EDGE_SUCC (bb, 0);
          edge e1 = EDGE_SUCC (bb, 1);
@@ -2315,8 +2317,6 @@ reorder_basic_blocks_simple (void)
          edges[n++] = e0;
          edges[n++] = e1;
        }
-      else if (single_succ_p (bb))
-       edges[n++] = EDGE_SUCC (bb, 0);
     }
 
   /* Sort the edges, the most desirable first.  When optimizing for size
-- 
1.9.3

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