Fixed infinite loop on find_last_node_before_loop

Happened when a loop was predicted not to be taken

1 files changed, 6 insertions, 3 deletions

diff --git a/backend/Duplicateaux.ml b/backend/Duplicateaux.ml
index 4684d870..98a638f3 100644
--- a/backend/Duplicateaux.ml
+++ b/backend/Duplicateaux.ml
@@ -624,6 +624,7 @@ type innerLoop = {
    * branches leading to a goto backedge
    * Such cases usually happen after a tail-duplication *)
   sb_final: P.t option; (* if the innerloop wraps a superblock, this is its final instruction *)
+    (* may be None if we predict that we do not loop *)
 }
 
 let print_pset = LICMaux.pp_pset
@@ -727,9 +728,11 @@ let rec find_last_node_before_loop code node trace is_loop_header =
     get_some @@ PTree.get n is_loop_header && HashedSet.PSet.contains trace n) rtl_succ in 
   match headers with
   | [] -> (
-      match (rtl_successors_pref @@ get_some @@ PTree.get node code) with
+      let next_nodes = List.filter (fun n -> HashedSet.PSet.contains trace n)
+        (rtl_successors_pref @@ get_some @@ PTree.get node code) in
+      match next_nodes with
       | [n] -> find_last_node_before_loop code n trace is_loop_header
-      | _ -> None
+      | _ -> None (* May happen when we predict that a loop is not taken *)
     )
   | [h] -> Some node
   | _ -> failwith "Multiple branches leading to a loop"
@@ -897,7 +900,7 @@ let unroll_inner_loop_body code revmap iloop =
     debug "Too many nodes in the loop body (%d > %d)" (List.length body) limit; debug_flag := false;
     (code, revmap)
   end else if not @@ is_some iloop.sb_final then begin
-    debug "The loop body does not form a superblock"; debug_flag := false;
+    debug "The loop body does not form a superblock OR we have predicted that we do not loop"; debug_flag := false;
     (code, revmap)
   end else
     let (code2, revmap2, dupbody, fwmap) = clone code revmap body in