tree-cfg.c (assert_unreachable_fallthru_edge_p): New function.

	* tree-cfg.c (assert_unreachable_fallthru_edge_p): New function.
	* tree-cfg.h (assert_unreachable_fallthru_edge_p): New prototype.
	* tree-vrp.c (all_imm_uses_in_stmt_or_feed_cond): New function.
	(remove_range_assertions): If ASSERT_EXPR_VAR has no other immediate
	uses but in the condition and ASSERT_EXPR and the other successor of
	the predecessor bb is __builtin_unreachable (), set_range_info of the
	ASSERT_EXPR_VAR to the range info of the ASSERT_EXPR's lhs.

From-SVN: r204255

1 files changed, 44 insertions, 0 deletions

diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index d705657..d646693 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -381,6 +381,50 @@ computed_goto_p (gimple t)
 	  && TREE_CODE (gimple_goto_dest (t)) != LABEL_DECL);
 }
 
+/* Returns true for edge E where e->src ends with a GIMPLE_COND and
+   the other edge points to a bb with just __builtin_unreachable ().
+   I.e. return true for C->M edge in:
+   <bb C>:
+   ...
+   if (something)
+     goto <bb N>;
+   else
+     goto <bb M>;
+   <bb N>:
+   __builtin_unreachable ();
+   <bb M>:  */
+
+bool
+assert_unreachable_fallthru_edge_p (edge e)
+{
+  basic_block pred_bb = e->src;
+  gimple last = last_stmt (pred_bb);
+  if (last && gimple_code (last) == GIMPLE_COND)
+    {
+      basic_block other_bb = EDGE_SUCC (pred_bb, 0)->dest;
+      if (other_bb == e->dest)
+	other_bb = EDGE_SUCC (pred_bb, 1)->dest;
+      if (EDGE_COUNT (other_bb->succs) == 0)
+	{
+	  gimple_stmt_iterator gsi = gsi_after_labels (other_bb);
+	  gimple stmt;
+
+	  if (gsi_end_p (gsi))
+	    return false;
+	  stmt = gsi_stmt (gsi);
+	  if (is_gimple_debug (stmt))
+	    {
+	      gsi_next_nondebug (&gsi);
+	      if (gsi_end_p (gsi))
+		return false;
+	      stmt = gsi_stmt (gsi);
+	    }
+	  return gimple_call_builtin_p (stmt, BUILT_IN_UNREACHABLE);
+	}
+    }
+  return false;
+}
+
 
 /* Search the CFG for any computed gotos.  If found, factor them to a
    common computed goto site.  Also record the location of that site so