From ce4191eed16e15397cc09bba95d8ef603ba05359 Mon Sep 17 00:00:00 2001
From: Roger Sayle <roger@eyesopen.com>
Date: Sun, 9 Nov 2003 14:33:20 +0000
Subject: [PATCH] loop.c (check_dbra_loop): Try swapping the comparison
 operands of the loop condition to identify a...

	* 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.

From-SVN: r73391
---
 gcc/ChangeLog |  6 ++++++
 gcc/loop.c    | 16 ++++++++++++++++
 gcc/unroll.c  | 15 ++++++++++++++-
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a050922f7aa..8603eb5aeb6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2003-11-09  Roger Sayle  <roger@eyesopen.com>
+
+	* 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.
+
 2003-11-09  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* config/sparc/sparc.h (TARGET_CPU_CPP_BUILTINS): Fix sparc vs
diff --git a/gcc/loop.c b/gcc/loop.c
index 667833d64a5..159906d3747 100644
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -8017,6 +8017,22 @@ check_dbra_loop (struct loop *loop, int insn_count)
 	break;
     }
 
+  /* Try swapping the comparison to identify a suitable biv.  */
+  if (!bl)
+    for (bl = ivs->list; bl; bl = bl->next)
+      if (bl->biv_count == 1
+	  && ! bl->biv->maybe_multiple
+	  && bl->biv->dest_reg == XEXP (comparison, 1)
+	  && ! reg_used_between_p (regno_reg_rtx[bl->regno], bl->biv->insn,
+				   first_compare))
+	{
+	  comparison = gen_rtx_fmt_ee (swap_condition (GET_CODE (comparison)),
+				       VOIDmode,
+				       XEXP (comparison, 1),
+				       XEXP (comparison, 0));
+	  break;
+	}
+
   if (! bl)
     return 0;
 
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 ();