re PR tree-optimization/21562 (Quiet bad codegen (unrolling + tail call interaction))

	PR tree-optimization/21562
	* cfgexpand.c (construct_init_block): Deal properly with the case
	of entry edge not pointing to very first basic block.

From-SVN: r100305

1 files changed, 16 insertions, 13 deletions

diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index cd9829e..4e4a8e2 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1157,22 +1157,25 @@ static basic_block
 construct_init_block (void)
 {
   basic_block init_block, first_block;
-  edge e = NULL, e2;
-  edge_iterator ei;
+  edge e = NULL;
+  int flags;
 
-  FOR_EACH_EDGE (e2, ei, ENTRY_BLOCK_PTR->succs)
-    {
-      /* Clear EDGE_EXECUTABLE.  This flag is never used in the backend.
+  /* Multiple entry points not supported yet.  */
+  gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR->succs) == 1);
 
-	 For all other blocks this edge flag is cleared while expanding
-	 a basic block in expand_gimple_basic_block, but there we never
-	 looked at the successors of the entry block.
-	 This caused PR17513.  */
-      e2->flags &= ~EDGE_EXECUTABLE;
+  e = EDGE_SUCC (ENTRY_BLOCK_PTR, 0);
 
-      if (e2->dest == ENTRY_BLOCK_PTR->next_bb)
-	e = e2;
+  /* When entry edge points to first basic block, we don't need jump,
+     otherwise we have to jump into proper target.  */
+  if (e && e->dest != ENTRY_BLOCK_PTR->next_bb)
+    {
+      tree label = tree_block_label (e->dest);
+
+      emit_jump (label_rtx (label));
+      flags = 0;
     }
+  else
+    flags = EDGE_FALLTHRU;
 
   init_block = create_basic_block (NEXT_INSN (get_insns ()),
 				   get_last_insn (),
@@ -1183,7 +1186,7 @@ construct_init_block (void)
     {
       first_block = e->dest;
       redirect_edge_succ (e, init_block);
-      e = make_edge (init_block, first_block, EDGE_FALLTHRU);
+      e = make_edge (init_block, first_block, flags);
     }
   else
     e = make_edge (init_block, EXIT_BLOCK_PTR, EDGE_FALLTHRU);