m68k.c (output_btst): Use `movew to ccr' when useful.

2007-04-18  Philippe De Muyter  <phdm@macqel.be>

	* config/m68k/m68k.c (output_btst): Use `movew to ccr' when useful.

From-SVN: r123959

gcc/ChangeLog

+2007-04-18  Philippe De Muyter  <phdm@macqel.be>
+
+	* config/m68k/m68k.c (output_btst): Use `movew to ccr' when useful.
+
 2007-04-18  Dirk Mueller  <dmueller@suse.de>
 
 	PR diagnostic/31227

gcc/config/m68k/m68k.c

@@ -1550,6 +1550,27 @@ output_btst (rtx *operands, rtx countop, rtx dataop, rtx insn, int signpos)
       if (count == 7
 	  && next_insn_tests_no_inequality (insn))
 	return "tst%.b %1";
+      /* Try to use `movew to ccr' followed by the appropriate branch insn.
+         On some m68k variants unfortunately that's slower than btst.
+         On 68000 and higher, that should also work for all HImode operands. */
+      if (TUNE_CPU32 || TARGET_COLDFIRE || optimize_size)
+	{
+	  if (count == 3 && DATA_REG_P (operands[1])
+	      && next_insn_tests_no_inequality (insn))
+	    {
+	    cc_status.flags = CC_NOT_NEGATIVE | CC_Z_IN_NOT_N | CC_NO_OVERFLOW;
+	    return "move%.w %1,%%ccr";
+	    }
+	  if (count == 2 && DATA_REG_P (operands[1])
+	      && next_insn_tests_no_inequality (insn))
+	    {
+	    cc_status.flags = CC_NOT_NEGATIVE | CC_INVERTED | CC_NO_OVERFLOW;
+	    return "move%.w %1,%%ccr";
+	    }
+	  /* count == 1 followed by bvc/bvs and
+	     count == 0 followed by bcc/bcs are also possible, but need
+	     m68k-specific CC_Z_IN_NOT_V and CC_Z_IN_NOT_C flags. */
+	}
 
       cc_status.flags = CC_NOT_NEGATIVE;
     }