[turbofan] Implement OSR for outer loops.

src/compiler/register-allocator.cc

Index: src/compiler/register-allocator.cc
diff --git a/src/compiler/register-allocator.cc b/src/compiler/register-allocator.cc
index a4f3c6ef0ad5d8372ce99e18058b6f1cf0521710..c28fa497fe46ae45063b4b35313ff1da99a148ed 100644
--- a/src/compiler/register-allocator.cc
+++ b/src/compiler/register-allocator.cc
@@ -1082,7 +1082,7 @@ void RegisterAllocator::MeetRegisterConstraintsForLastInstructionInBlock(
       AllocateFixed(output, -1, false);
       // This value is produced on the stack, we never need to spill it.
       if (output->IsStackSlot()) {
-        DCHECK(output->index() < 0);
+        DCHECK(output->index() < frame_->GetSpillSlotCount());
         range->SetSpillOperand(output);
         range->SetSpillStartIndex(end);
         assigned = true;
@@ -1148,7 +1148,7 @@ void RegisterAllocator::MeetConstraintsBetween(Instruction* first,
 
           // This value is produced on the stack, we never need to spill it.
           if (first_output->IsStackSlot()) {
-            DCHECK(first_output->index() < 0);
+            DCHECK(first_output->index() < frame_->GetSpillSlotCount());
             range->SetSpillOperand(first_output);
             range->SetSpillStartIndex(gap_index - 1);
             assigned = true;