[backport from gcc-4.8/trunk r186361 <mikpe@it.uu.se>]

From: Andreas Schwab <schwab at linux-m68k dot org>
Subject: m68k: add bswapsi2 expander
Date: Thu, 12 Apr 2012 00:03:05 +0200
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

The default expansion of bswapsi2 (and bswapdi2) is pretty suboptimal.
Tested on m68k-linux.

Andreas.

gcc/

2012-04-11  Andreas Schwab  <schwab@linux-m68k.org>

	* config/m68k/m68k.md (rotrhi3+1): Name it rotrhi_lowpart.
	(bswapsi2): New expander.

--- gcc-4.7.0/gcc/config/m68k/m68k.md.~1~	2011-11-27 00:59:56.000000000 +0100
+++ gcc-4.7.0/gcc/config/m68k/m68k.md	2012-06-09 21:17:22.000000000 +0200
@@ -5475,7 +5475,7 @@ (define_insn "rotrhi3"
   "!TARGET_COLDFIRE"
   "ror%.w %2,%0")
 
-(define_insn ""
+(define_insn "rotrhi_lowpart"
   [(set (strict_low_part (match_operand:HI 0 "register_operand" "+d"))
 	(rotatert:HI (match_dup 0)
 		     (match_operand:HI 1 "general_operand" "dI")))]
@@ -5495,6 +5495,19 @@ (define_insn ""
 		     (match_operand:QI 1 "general_operand" "dI")))]
   "!TARGET_COLDFIRE"
   "ror%.b %1,%0")
+
+(define_expand "bswapsi2"
+  [(set (match_operand:SI 0 "register_operand")
+	(bswap:SI (match_operand:SI 1 "register_operand")))]
+  "!TARGET_COLDFIRE"
+{
+  rtx x = operands[0];
+  emit_move_insn (x, operands[1]);
+  emit_insn (gen_rotrhi_lowpart (gen_lowpart (HImode, x), GEN_INT (8)));
+  emit_insn (gen_rotlsi3 (x, x, GEN_INT (16)));
+  emit_insn (gen_rotrhi_lowpart (gen_lowpart (HImode, x), GEN_INT (8)));
+  DONE;
+})
 
 
 ;; Bit set/clear in memory byte.