jump.c (duplicate_loop_exit_test): Better test for jumps entering the loop; create loop pre_header.

	* jump.c (duplicate_loop_exit_test): Better test for jumps
	entering the loop; create loop pre_header.

From-SVN: r44512

1 files changed, 12 insertions, 3 deletions

diff --git a/gcc/jump.c b/gcc/jump.c
index ddef4a1..dd099f2 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -305,6 +305,7 @@ duplicate_loop_exit_test (loop_start)
   rtx lastexit;
   int max_reg = max_reg_num ();
   rtx *reg_map = 0;
+  rtx loop_pre_header_label;
 
   /* Scan the exit code.  We do not perform this optimization if any insn:
 
@@ -405,6 +406,7 @@ duplicate_loop_exit_test (loop_start)
 	    reg_map[REGNO (reg)] = gen_reg_rtx (GET_MODE (reg));
 	  }
       }
+  loop_pre_header_label = gen_label_rtx ();
 
   /* Now copy each insn.  */
   for (insn = exitcode; insn != lastexit; insn = NEXT_INSN (insn))
@@ -475,9 +477,14 @@ duplicate_loop_exit_test (loop_start)
 		  /* The jump_insn after loop_start should be followed
 		     by barrier and loopback label.  */
 		  if (prev_nonnote_insn (label)
-		      && (PREV_INSN (prev_nonnote_insn (label))
-			  == NEXT_INSN (loop_start)))
-		    predict_insn_def (copy, PRED_LOOP_HEADER, TAKEN);
+		      && (prev_nonnote_insn (prev_nonnote_insn (label))
+			  == next_nonnote_insn (loop_start)))
+		    {
+		      predict_insn_def (copy, PRED_LOOP_HEADER, TAKEN);
+		      /* To keep pre-header, we need to redirect all loop
+		         entrances before the LOOP_BEG note.  */
+		      redirect_jump (copy, loop_pre_header_label, 0);
+		    }
 		  else
 		    predict_insn_def (copy, PRED_LOOP_HEADER, NOT_TAKEN);
 		}
@@ -512,6 +519,8 @@ duplicate_loop_exit_test (loop_start)
       emit_barrier_before (loop_start);
     }
 
+  emit_label_before (loop_pre_header_label, loop_start);
+
   /* Now scan from the first insn we copied to the last insn we copied
      (copy) for new pseudo registers.  Do this after the code to jump to
      the end label since that might create a new pseudo too.  */