From 44fef04ab18f57111e7d9f7dcd88d76a3c7bfc09 Mon Sep 17 00:00:00 2001
From: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date: Mon, 3 Aug 2015 08:14:42 +0000
Subject: [RTL-ifcvt] Improve conditional select ops on immediates

	* ifcvt.c (noce_try_store_flag_constants): Make logic of the case
	when diff == STORE_FLAG_VALUE or diff == -STORE_FLAG_VALUE more
	explicit.  Prefer to add the flag whenever possible.
	(noce_process_if_block): Try noce_try_store_flag_constants before
	noce_try_cmove.

	* gcc.target/aarch64/csel_bfx_1.c: New test.
	* gcc.target/aarch64/csel_imms_inc_1.c: Likewise.

From-SVN: r226491
---
 gcc/ifcvt.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 52 insertions(+), 11 deletions(-)

(limited to 'gcc/ifcvt.c')

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 2d97cc5..1f29646 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -1159,9 +1159,10 @@ noce_try_store_flag_constants (struct noce_if_info *if_info)
 {
   rtx target;
   rtx_insn *seq;
-  int reversep;
+  bool reversep;
   HOST_WIDE_INT itrue, ifalse, diff, tmp;
-  int normalize, can_reverse;
+  int normalize;
+  bool can_reverse;
   machine_mode mode;
 
   if (CONST_INT_P (if_info->a)
@@ -1170,6 +1171,7 @@ noce_try_store_flag_constants (struct noce_if_info *if_info)
       mode = GET_MODE (if_info->x);
       ifalse = INTVAL (if_info->a);
       itrue = INTVAL (if_info->b);
+      bool subtract_flag_p = false;
 
       diff = (unsigned HOST_WIDE_INT) itrue - ifalse;
       /* Make sure we can represent the difference between the two values.  */
@@ -1182,23 +1184,61 @@ noce_try_store_flag_constants (struct noce_if_info *if_info)
       can_reverse = (reversed_comparison_code (if_info->cond, if_info->jump)
 		     != UNKNOWN);
 
-      reversep = 0;
+      reversep = false;
       if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
-	normalize = 0;
+	{
+	  normalize = 0;
+	  /* We could collapse these cases but it is easier to follow the
+	     diff/STORE_FLAG_VALUE combinations when they are listed
+	     explicitly.  */
+
+	  /* test ? 3 : 4
+	     => 4 + (test != 0).  */
+	  if (diff < 0 && STORE_FLAG_VALUE < 0)
+	      reversep = false;
+	  /* test ? 4 : 3
+	     => can_reverse  | 4 + (test == 0)
+		!can_reverse | 3 - (test != 0).  */
+	  else if (diff > 0 && STORE_FLAG_VALUE < 0)
+	    {
+	      reversep = can_reverse;
+	      subtract_flag_p = !can_reverse;
+	    }
+	  /* test ? 3 : 4
+	     => can_reverse  | 3 + (test == 0)
+		!can_reverse | 4 - (test != 0).  */
+	  else if (diff < 0 && STORE_FLAG_VALUE > 0)
+	    {
+	      reversep = can_reverse;
+	      subtract_flag_p = !can_reverse;
+	    }
+	  /* test ? 4 : 3
+	     => 4 + (test != 0).  */
+	  else if (diff > 0 && STORE_FLAG_VALUE > 0)
+	    reversep = false;
+	  else
+	    gcc_unreachable ();
+	}
       else if (ifalse == 0 && exact_log2 (itrue) >= 0
 	       && (STORE_FLAG_VALUE == 1
 		   || if_info->branch_cost >= 2))
 	normalize = 1;
       else if (itrue == 0 && exact_log2 (ifalse) >= 0 && can_reverse
 	       && (STORE_FLAG_VALUE == 1 || if_info->branch_cost >= 2))
-	normalize = 1, reversep = 1;
+	{
+	  normalize = 1;
+	  reversep = true;
+	}
       else if (itrue == -1
 	       && (STORE_FLAG_VALUE == -1
 		   || if_info->branch_cost >= 2))
 	normalize = -1;
       else if (ifalse == -1 && can_reverse
 	       && (STORE_FLAG_VALUE == -1 || if_info->branch_cost >= 2))
-	normalize = -1, reversep = 1;
+	{
+	  normalize = -1;
+	  reversep = true;
+	}
       else if ((if_info->branch_cost >= 2 && STORE_FLAG_VALUE == -1)
 	       || if_info->branch_cost >= 3)
 	normalize = -1;
@@ -1223,9 +1263,9 @@ noce_try_store_flag_constants (struct noce_if_info *if_info)
 	 =>   x = 3 + (test == 0);  */
       if (diff == STORE_FLAG_VALUE || diff == -STORE_FLAG_VALUE)
 	{
-	  target = expand_simple_binop (mode,
-					(diff == STORE_FLAG_VALUE
-					 ? PLUS : MINUS),
+	  /* Always use ifalse here.  It should have been swapped with itrue
+	     when appropriate when reversep is true.  */
+	  target = expand_simple_binop (mode, subtract_flag_p ? MINUS : PLUS,
 					gen_int_mode (ifalse, mode), target,
 					if_info->x, 0, OPTAB_WIDEN);
 	}
@@ -2731,13 +2771,14 @@ noce_process_if_block (struct noce_if_info *if_info)
     goto success;
   if (noce_try_abs (if_info))
     goto success;
+  if (!targetm.have_conditional_execution ()
+      && noce_try_store_flag_constants (if_info))
+    goto success;
   if (HAVE_conditional_move
       && noce_try_cmove (if_info))
     goto success;
   if (! targetm.have_conditional_execution ())
     {
-      if (noce_try_store_flag_constants (if_info))
-	goto success;
       if (noce_try_addcc (if_info))
 	goto success;
       if (noce_try_store_flag_mask (if_info))
-- 
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