Fixed two register allocator bugs (off-by-one error/failure propagation).

src/lithium-allocator.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 821 matching lines @@
         LUnallocated* input_copy = cur_input->CopyUnconstrained(zone());
         bool is_tagged = HasTaggedValue(cur_input->virtual_register());
         AllocateFixed(cur_input, gap_index + 1, is_tagged);
         AddConstraintsGapMove(gap_index, input_copy, cur_input);
       } else if (cur_input->policy() == LUnallocated::WRITABLE_REGISTER) {
         // The live range of writable input registers always goes until the end
         // of the instruction.
         ASSERT(!cur_input->IsUsedAtStart());
 
         LUnallocated* input_copy = cur_input->CopyUnconstrained(zone());
-        cur_input->set_virtual_register(GetVirtualRegister());
+        int vreg = GetVirtualRegister();
         if (!AllocationOk()) return;
+        cur_input->set_virtual_register(vreg);
 
         if (RequiredRegisterKind(input_copy->virtual_register()) ==
             DOUBLE_REGISTERS) {
           double_artificial_registers_.Add(
               cur_input->virtual_register() - first_artificial_register_,
               zone_);
         }
 
         AddConstraintsGapMove(gap_index, input_copy, cur_input);
       }
@@ skipping 1063 matching lines @@
     SpillBetween(current, current->Start(), register_use->pos());
     return;
   }
 
   if (block_pos[reg].Value() < current->End().Value()) {
     // Register becomes blocked before the current range end. Split before that
     // position.
     LiveRange* tail = SplitBetween(current,
                                    current->Start(),
                                    block_pos[reg].InstructionStart());
+    if (!AllocationOk()) return;
     AddToUnhandledSorted(tail);
   }
 
   // Register reg is not blocked for the whole range.
   ASSERT(block_pos[reg].Value() >= current->End().Value());
   TraceAlloc("Assigning blocked reg %s to live range %d\n",
              RegisterName(reg),
              current->id());
   SetLiveRangeAssignedRegister(current, reg, mode_, zone_);
 
@@ skipping 10 matching lines @@
   LifetimePosition split_pos = current->Start();
   for (int i = 0; i < active_live_ranges_.length(); ++i) {
     LiveRange* range = active_live_ranges_[i];
     if (range->assigned_register() == reg) {
       UsePosition* next_pos = range->NextRegisterPosition(current->Start());
       if (next_pos == NULL) {
         SpillAfter(range, split_pos);
       } else {
         SpillBetween(range, split_pos, next_pos->pos());
       }
+      if (!AllocationOk()) return;
       ActiveToHandled(range);
       --i;
     }
   }
 
   for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
     LiveRange* range = inactive_live_ranges_[i];
     ASSERT(range->End().Value() > current->Start().Value());
     if (range->assigned_register() == reg && !range->IsFixed()) {
       LifetimePosition next_intersection = range->FirstIntersection(current);
       if (next_intersection.IsValid()) {
         UsePosition* next_pos = range->NextRegisterPosition(current->Start());
         if (next_pos == NULL) {
           SpillAfter(range, split_pos);
         } else {
           next_intersection = Min(next_intersection, next_pos->pos());
           SpillBetween(range, split_pos, next_intersection);
         }
+        if (!AllocationOk()) return;
         InactiveToHandled(range);
         --i;
       }
     }
   }
 }
 
 
 bool LAllocator::IsBlockBoundary(LifetimePosition pos) {
   return pos.IsInstructionStart() &&
       InstructionAt(pos.InstructionIndex())->IsLabel();
 }
 
 
 LiveRange* LAllocator::SplitRangeAt(LiveRange* range, LifetimePosition pos) {
   ASSERT(!range->IsFixed());
   TraceAlloc("Splitting live range %d at %d\n", range->id(), pos.Value());
 
   if (pos.Value() <= range->Start().Value()) return range;
 
   // We can't properly connect liveranges if split occured at the end
   // of control instruction.
   ASSERT(pos.IsInstructionStart() ||
          !chunk_->instructions()->at(pos.InstructionIndex())->IsControl());
 
-  LiveRange* result = LiveRangeFor(GetVirtualRegister());
+  int vreg = GetVirtualRegister();
   if (!AllocationOk()) return NULL;
+  LiveRange* result = LiveRangeFor(vreg);
   range->SplitAt(pos, result, zone_);
   return result;
 }
 
 
 LiveRange* LAllocator::SplitBetween(LiveRange* range,
                                     LifetimePosition start,
                                     LifetimePosition end) {
   ASSERT(!range->IsFixed());
   TraceAlloc("Splitting live range %d in position between [%d, %d]\n",
@@ skipping 56 matching lines @@
   if (!AllocationOk()) return;
 
   if (second_part->Start().Value() < end.Value()) {
     // The split result intersects with [start, end[.
     // Split it at position between ]start+1, end[, spill the middle part
     // and put the rest to unhandled.
     LiveRange* third_part = SplitBetween(
         second_part,
         second_part->Start().InstructionEnd(),
         end.PrevInstruction().InstructionEnd());
+    if (!AllocationOk()) return;
 
     ASSERT(third_part != second_part);
 
     Spill(second_part);
     AddToUnhandledSorted(third_part);
   } else {
     // The split result does not intersect with [start, end[.
     // Nothing to spill. Just put it to unhandled as whole.
     AddToUnhandledSorted(second_part);
   }
@@ skipping 27 matching lines @@
     LiveRange* current = live_ranges()->at(i);
     if (current != NULL) current->Verify();
   }
 }
 
 
 #endif
 
 
 } }  // namespace v8::internal