From: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Mon, 17 Jul 2000 08:55:51 +0000 (+0000)
Subject:         * h8300.c (two_insn_adds_subs_operand): Improve code for detecting
X-Git-Tag: upstream/4.9.2~100300
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3c4d0c203a202b6aeda955a5f8441eea8314eaac;p=platform%2Fupstream%2Flinaro-gcc.git

    * h8300.c (two_insn_adds_subs_operand): Improve code for detecting
        profitable adds/subs sequences.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@35081 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0d81edd..1e3ac96 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -29,6 +29,9 @@ Mon Jul 17 02:37:06 2000  Marc Espie <espie@openbsd.org>
 
 2000-07-17  Kazu Hirata  <kazu@hxi.com>
 
+	* h8300.c (two_insn_adds_subs_operand): Improve code for detecting
+	profitable adds/subs sequences.
+
 	* fold-const.c: Fix comment typos.
 
 2000-07-16  Laurynas Biveinis  <lauras@softhome.net>
diff --git a/gcc/config/h8300/h8300.c b/gcc/config/h8300/h8300.c
index 4eb304e..ba46d04 100644
--- a/gcc/config/h8300/h8300.c
+++ b/gcc/config/h8300/h8300.c
@@ -626,25 +626,46 @@ call_insn_operand (op, mode)
   return 0;
 }
 
+/* Return 1 if a addition/subtraction of a constant integer can be
+   transformed into two consecutive adds/subs that are faster than the
+   straightforward way.  Otherwise, return 0. */
+
 int
 two_insn_adds_subs_operand (op, mode)
      rtx op;
-     enum machine_mode mode ATTRIBUTE_UNUSED;
+     enum machine_mode mode;
 {
   if (GET_CODE (op) == CONST_INT)
     {
       HOST_WIDE_INT value = INTVAL (op);
 
+      /* Force VALUE to be positive so that we do not have to consider
+         the negative case.  */
+      if (value < 0)
+	value = -value;
       if (TARGET_H8300H || TARGET_H8300S)
 	{
-	  if (value >= -8 && value < -4 && value != -7)
-	    return 1;
-	  if (value > 4 && value <= 8 && value != 7)
-	    return 1;
+	  /* A constant addition/subtraction takes 2 states in QImode,
+	     4 states in HImode, and 6 states in SImode.  Thus, the
+	     only case we can win is when SImode is used, in which
+	     case, two adds/subs is used, taking 4 states.  */
+	  if (mode == SImode
+	      && (value == 2 + 1
+		  || value == 4 + 1
+		  || value == 4 + 2
+		  || value == 4 + 4))
+	      return 1;
 	}
       else
 	{
-	  if (value == -4 || value == -3 || value == 3 || value == 4)
+	  /* A constant addition/subtraction takes 2 states in
+	     QImode. It takes 6 states in HImode, requiring the
+	     constant to be loaded to a register first, and a lot more
+	     in SImode.  Thus the only case we can win is when either
+	     HImode or SImode is used.  */
+	  if (mode != QImode
+	      && (value == 2 + 1
+		  || value == 2 + 2))
 	    return 1;
 	}
     }