Re: [PATCH][auto-inc-dec.c] Account for cost of move operation in FORM_PRE_ADD and FORM_POST_ADD cases

[Kyrill Tkachov <kyrylo.tkachov@arm.com>]

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On 26/10/15 11:28, Bernd Schmidt wrote:
> On 10/26/2015 12:12 PM, Bernd Schmidt wrote:
>>
>> But isn't that balanced by the fact that it doesn't seem to take into
>> account the gain of removing the inc_insn either? So I think this can't
>> be right.
>
> Argh, misread the code. The patch is OK with the change I suggested.
>

Thanks!
Here's what I committed with r229344.

Kyrill

2015-10-26  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * auto-inc-dec.c (insert_move_insn_before): Delete.
     (attempt_change): Remember to cost the simple move in the
     FORM_PRE_ADD and FORM_POST_ADD cases.

>
> Bernd
>


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commit cc7c4748eac1f9d59ceb5393132c098aba99765d
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Fri Oct 16 13:46:51 2015 +0100

    [auto-inc-dec.c] Account for cost of move operation in FORM_PRE_ADD and FORM_POST_ADD cases

diff --git a/gcc/auto-inc-dec.c b/gcc/auto-inc-dec.c
index e003b13..9f7c8e0 100644
--- a/gcc/auto-inc-dec.c
+++ b/gcc/auto-inc-dec.c
@@ -439,24 +439,6 @@ move_dead_notes (rtx_insn *to_insn, rtx_insn *from_insn, rtx pattern)
     }
 }
 
-
-/* Create a mov insn DEST_REG <- SRC_REG and insert it before
-   NEXT_INSN.  */
-
-static rtx_insn *
-insert_move_insn_before (rtx_insn *next_insn, rtx dest_reg, rtx src_reg)
-{
-  rtx_insn *insns;
-
-  start_sequence ();
-  emit_move_insn (dest_reg, src_reg);
-  insns = get_insns ();
-  end_sequence ();
-  emit_insn_before (insns, next_insn);
-  return insns;
-}
-
-
 /* Change mem_insn.mem_loc so that uses NEW_ADDR which has an
    increment of INC_REG.  To have reached this point, the change is a
    legitimate one from a dataflow point of view.  The only questions
@@ -490,8 +472,21 @@ attempt_change (rtx new_addr, rtx inc_reg)
 
   old_cost = (set_src_cost (mem, mode, speed)
 	      + set_rtx_cost (PATTERN (inc_insn.insn), speed));
+
   new_cost = set_src_cost (mem_tmp, mode, speed);
 
+  /* In the FORM_PRE_ADD and FORM_POST_ADD cases we emit an extra move
+     whose cost we should account for.  */
+  if (inc_insn.form == FORM_PRE_ADD
+      || inc_insn.form == FORM_POST_ADD)
+    {
+      start_sequence ();
+      emit_move_insn (inc_insn.reg_res, inc_insn.reg0);
+      mov_insn = get_insns ();
+      end_sequence ();
+      new_cost += seq_cost (mov_insn, speed);
+    }
+
   /* The first item of business is to see if this is profitable.  */
   if (old_cost < new_cost)
     {
@@ -522,8 +517,8 @@ attempt_change (rtx new_addr, rtx inc_reg)
       /* Replace the addition with a move.  Do it at the location of
 	 the addition since the operand of the addition may change
 	 before the memory reference.  */
-      mov_insn = insert_move_insn_before (inc_insn.insn,
-					  inc_insn.reg_res, inc_insn.reg0);
+      gcc_assert (mov_insn);
+      emit_insn_before (mov_insn, inc_insn.insn);
       move_dead_notes (mov_insn, inc_insn.insn, inc_insn.reg0);
 
       regno = REGNO (inc_insn.reg_res);
@@ -548,8 +543,8 @@ attempt_change (rtx new_addr, rtx inc_reg)
       break;
 
     case FORM_POST_ADD:
-      mov_insn = insert_move_insn_before (mem_insn.insn,
-					  inc_insn.reg_res, inc_insn.reg0);
+      gcc_assert (mov_insn);
+      emit_insn_before (mov_insn, mem_insn.insn);
       move_dead_notes (mov_insn, inc_insn.insn, inc_insn.reg0);
 
       /* Do not move anything to the mov insn because the instruction