[PR112918][LRA]: Fixing IRA ICE on m68k

Some GCC tests on m68K port of LRA is failed on `maximum number of
generated reload insns per insn achieved`.  The problem is in that for
subreg reload LRA can not narrow reg class more from ALL_REGS to
GENERAL_REGS and then to data regs or address regs.  The patch permits
narowing reg class from reload insns if this results in succesful
matching of reg operand.

gcc/ChangeLog:

	PR rtl-optimization/112918
	* lra-constraints.cc (SMALL_REGISTER_CLASS_P): Move before in_class_p.
	(in_class_p): Restrict condition for narrowing class in case of
	allow_all_reload_class_changes_p.
	(process_alt_operands): Pass true for
	allow_all_reload_class_changes_p in calls of in_class_p.
	(curr_insn_transform): Ditto for reg operand win.

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index da7e1748d75413e7a04214554eb09084236582bd..05479ab98dd5a803952786564834d767590e33a4 100644 (file)
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -261,6 +261,13 @@ enough_allocatable_hard_regs_p (enum reg_class reg_class,
   return false;
 }
 
+/* True if C is a non-empty register class that has too few registers
+   to be safely used as a reload target class. */
+#define SMALL_REGISTER_CLASS_P(C)              \
+  (ira_class_hard_regs_num [(C)] == 1          \
+   || (ira_class_hard_regs_num [(C)] >= 1      \
+       && targetm.class_likely_spilled_p (C)))
+
 /* Return true if REG satisfies (or will satisfy) reg class constraint
    CL.  Use elimination first if REG is a hard register.  If REG is a
    reload pseudo created by this constraints pass, assume that it will
@@ -318,7 +325,11 @@ in_class_p (rtx reg, enum reg_class cl, enum reg_class *new_class,
       common_class = ira_reg_class_subset[rclass][cl];
       if (new_class != NULL)
        *new_class = common_class;
-      return enough_allocatable_hard_regs_p (common_class, reg_mode);
+      return (enough_allocatable_hard_regs_p (common_class, reg_mode)
+             /* Do not permit reload insn operand matching (new_class == NULL
+                case) if the new class is too small.  */
+             && (new_class != NULL || common_class == rclass
+                 || !SMALL_REGISTER_CLASS_P (common_class)));
     }
 }
 
@@ -923,13 +934,6 @@ operands_match_p (rtx x, rtx y, int y_hard_regno)
    && GET_MODE_SIZE (MODE).is_constant ()      \
    && !targetm.cannot_force_const_mem (MODE, X))
 
-/* True if C is a non-empty register class that has too few registers
-   to be safely used as a reload target class. */
-#define SMALL_REGISTER_CLASS_P(C)              \
-  (ira_class_hard_regs_num [(C)] == 1          \
-   || (ira_class_hard_regs_num [(C)] >= 1      \
-       && targetm.class_likely_spilled_p (C)))
-
 /* If REG is a reload pseudo, try to make its class satisfying CL.  */
 static void
 narrow_reload_pseudo_class (rtx reg, enum reg_class cl)
@@ -2631,7 +2635,7 @@ process_alt_operands (int only_alternative)
                                    hard_regno[nop]))))
                        win = true;
                      else if (hard_regno[nop] < 0
-                              && in_class_p (op, this_alternative, NULL))
+                              && in_class_p (op, this_alternative, NULL, true))
                        win = true;
                    }
                  break;
@@ -2675,7 +2679,7 @@ process_alt_operands (int only_alternative)
                          reject++;
                        }
                      if (in_class_p (operand_reg[nop],
-                                     this_costly_alternative, NULL))
+                                     this_costly_alternative, NULL, true))
                        {
                          if (lra_dump_file != NULL)
                            fprintf
@@ -4388,7 +4392,7 @@ curr_insn_transform (bool check_only_p)
 
        if (REG_P (reg) && (regno = REGNO (reg)) >= FIRST_PSEUDO_REGISTER)
          {
-           bool ok_p = in_class_p (reg, goal_alt[i], &new_class);
+           bool ok_p = in_class_p (reg, goal_alt[i], &new_class, true);
 
            if (new_class != NO_REGS && get_reg_class (regno) != new_class)
              {