* loop.c (check_dbra_loop): Try swapping the comparison operands

	of the loop condition to identify a suitable induction variable.
	* unroll.c (loop_iterations): Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@73391 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 14 insertions, 1 deletions

diff --git a/gcc/unroll.c b/gcc/unroll.c
index 38659d461cb..cc415a795b6 100644
--- a/gcc/unroll.c
+++ b/gcc/unroll.c
@@ -3421,7 +3421,20 @@ loop_iterations (struct loop *loop)
 		 "Loop iterations: Iteration var not an integer.\n");
       return 0;
     }
-  else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT)
+
+  /* Try swapping the comparison to identify a suitable iv.  */
+  if (REG_IV_TYPE (ivs, REGNO (iteration_var)) != BASIC_INDUCT
+      && REG_IV_TYPE (ivs, REGNO (iteration_var)) != GENERAL_INDUCT
+      && GET_CODE (comparison_value) == REG
+      && REGNO (comparison_value) < ivs->n_regs)
+    {
+      rtx temp = comparison_value;
+      comparison_code = swap_condition (comparison_code);
+      comparison_value = iteration_var;
+      iteration_var = temp;
+    }
+
+  if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT)
     {
       if (REGNO (iteration_var) >= ivs->n_regs)
 	abort ();