From patchwork Tue Jul 19 21:41:59 2011
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Subject: RFA: patch to fix broken FRV target
From: Vladimir Makarov <vmakarov@redhat.com>
X-Patchwork-Id: 105546
Message-Id: <4E25FA27.1030200@redhat.com>
To: gcc-patches@gcc.gnu.org
Cc: nickc@redhat.com
Date: Tue, 19 Jul 2011 17:41:59 -0400

Currently, FRV port is broken.  It crashes on assertion in IRA because
the right pressure register classes can not be found.

I started work on this and found that register move cost for moving
between GPR_REGS (or QUAD_REGS) is too costly (40) although FRV
machine dependent code reports it cheap explicitly.

The cost is changed to the big value by the following code in 
reginfo.c::init_move_cost

           cost = last_move_cost[i][j];

           for (p2 = &reg_class_subclasses[j][0];
            *p2 != LIM_REG_CLASSES; p2++)
         if (*p2 != i && contains_reg_of_mode[*p2][m])
           cost = MAX (cost, move_cost[m][i][*p2]);

           for (p1 = &reg_class_subclasses[i][0];
            *p1 != LIM_REG_CLASSES; p1++)
         if (*p1 != j && contains_reg_of_mode[*p1][m])
           cost = MAX (cost, move_cost[m][*p1][j]);

when i==GPR_REGS and *p2 == GR8_REGS for example.  That happens
because moves from/to GR8_REGS, GR9_REGS, and other classes which are
subsets of GPR_REGS are treated too costly in frv_register_move_cost.

I could modify a code in init_move_cost ignoring costly subclasses when 
moves inside the superclass i s less costly than memory.  But I think it 
is wrong thing to do because it affects other targets in unknown now way 
and because I think we still need the right costs for GR8_REGS, ...

So I think the following patch is the right way to fix frv target.

Nick, is the patch ok for you?


2011-07-19  Vladimir Makarov <vmakarov@redhat.com>

     * config/frv/frv.c (frv_register_move_cost): Define explicitly
     costs for subclasses of GR_REGS.


Index: config/frv/frv.c
===================================================================
--- config/frv/frv.c    (revision 176462)
+++ config/frv/frv.c    (working copy)
@@ -6818,6 +6818,13 @@ frv_register_move_cost (enum machine_mod

      case QUAD_REGS:
      case GPR_REGS:
+    case GR8_REGS:
+    case GR9_REGS:
+    case GR89_REGS:
+    case FDPIC_REGS:
+    case FDPIC_FPTR_REGS:
+    case FDPIC_CALL_REGS:
+
        switch (to)
      {
      default:
@@ -6825,6 +6832,13 @@ frv_register_move_cost (enum machine_mod

      case QUAD_REGS:
      case GPR_REGS:
+    case GR8_REGS:
+    case GR9_REGS:
+    case GR89_REGS:
+    case FDPIC_REGS:
+    case FDPIC_FPTR_REGS:
+    case FDPIC_CALL_REGS:
+
        return LOW_COST;

      case FPR_REGS:
@@ -6844,6 +6858,13 @@ frv_register_move_cost (enum machine_mod

      case QUAD_REGS:
      case GPR_REGS:
+    case GR8_REGS:
+    case GR9_REGS:
+    case GR89_REGS:
+    case FDPIC_REGS:
+    case FDPIC_FPTR_REGS:
+    case FDPIC_CALL_REGS:
+
      case QUAD_ACC_REGS:
      case ACCG_REGS:
        return MEDIUM_COST;
@@ -6862,6 +6883,13 @@ frv_register_move_cost (enum machine_mod

      case QUAD_REGS:
      case GPR_REGS:
+    case GR8_REGS:
+    case GR9_REGS:
+    case GR89_REGS:
+    case FDPIC_REGS:
+    case FDPIC_FPTR_REGS:
+    case FDPIC_CALL_REGS:
+
        return MEDIUM_COST;
      }