poly_int: process_alt_operands

This patch makes process_alt_operands check that the mode sizes
are ordered, so that match_reload can validly treat them as subregs
of one another.

2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* lra-constraints.c (process_alt_operands): Reject matched
	operands whose sizes aren't ordered.
	(match_reload): Refer to this check here.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r256158

gcc/ChangeLog

@@ -2,6 +2,14 @@
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
 
+	* lra-constraints.c (process_alt_operands): Reject matched
+	operands whose sizes aren't ordered.
+	(match_reload): Refer to this check here.
+
+2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
 	* builtins.c (expand_ifn_atomic_compare_exchange_into_call): Assert
 	that the mode size is in the set {1, 2, 4, 8, 16}.
 

gcc/lra-constraints.c

@@ -933,6 +933,8 @@ match_reload (signed char out, signed char *ins, signed char *outs,
   push_to_sequence (*before);
   if (inmode != outmode)
     {
+      /* process_alt_operands has already checked that the mode sizes
+	 are ordered.  */
       if (partial_subreg_p (outmode, inmode))
 	{
 	  reg = new_in_reg
@@ -2112,6 +2114,13 @@ process_alt_operands (int only_alternative)
 		    len = 0;
 		    lra_assert (nop > m);
 
+		    /* Reject matches if we don't know which operand is
+		       bigger.  This situation would arguably be a bug in
+		       an .md pattern, but could also occur in a user asm.  */
+		    if (!ordered_p (GET_MODE_SIZE (biggest_mode[m]),
+				    GET_MODE_SIZE (biggest_mode[nop])))
+		      break;
+
 		    this_alternative_matches = m;
 		    m_hregno = get_hard_regno (*curr_id->operand_loc[m], false);
 		    /* We are supposed to match a previous operand.