Allow earlyclobbers in ira_get_dup_out_num

ira_get_dup_out_num punted on operands that are matched to
earlyclobber outputs:

	    /* It is better ignore an alternative with early clobber.  */
	    else if (*str == '&')
	      goto fail;

But I'm not sure why this is the right thing to do.  At this stage
we've established that *all* alternatives of interest require the
input to match the output, so

(a) the earlyclobber can only affect other operands and
(b) not tying the registers is bound to introduce a move

The code was part of the initial commit and so isn't obviously
related to a specific testcase.  Also, I can imagine LRA makes
a much better job of this situation than reload did.  (Certainly
SVE uses matched earlyclobbers extensively and I haven't seen any
problems.)

In case this turns out to regress something important: the main
case that matters for SVE is the one in which all alternatives
are earlyclobber.

2019-07-01  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* ira.c (ira_get_dup_out_num): Don't punt for earlyclobbers.
	Use recog_data to test for an output operand.

From-SVN: r272850

gcc/ChangeLog

 2019-07-01  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* ira.c (ira_get_dup_out_num): Don't punt for earlyclobbers.
+	Use recog_data to test for an output operand.
+
+2019-07-01  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* ira.c (ira_setup_alts): If any valid alternatives have zero cost,
 	exclude any others that are disparaged or that are bound to need
 	a reload or spill.

gcc/ira.c

@@ -1999,26 +1999,8 @@ ira_get_dup_out_num (int op_num, alternative_mask alts)
 	}
       if (original == -1)
 	goto fail;
-      dup = -1;
-      for (ignore_p = false, str = recog_data.constraints[original - '0'];
-	   *str != 0;
-	   str++)
-	if (ignore_p)
-	  {
-	    if (*str == ',')
-	      ignore_p = false;
-	  }
-	else if (*str == '#')
-	  ignore_p = true;
-	else if (! ignore_p)
-	  {
-	    if (*str == '=')
-	      dup = original - '0';
-	    /* It is better ignore an alternative with early clobber.  */
-	    else if (*str == '&')
-	      goto fail;
-	  }
-      if (dup >= 0)
+      dup = original - '0';
+      if (recog_data.operand_type[dup] == OP_OUT)
 	return dup;
     fail:
       if (use_commut_op_p)