[turbofan] Merge group spill ranges.

src/compiler/greedy-allocator.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/greedy-allocator.h"
 #include "src/compiler/register-allocator.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ skipping 461 matching lines @@
     TryAllocateCandidate(candidate);
   }
 
   for (size_t i = 0; i < allocations_.size(); ++i) {
     if (!allocations_[i]->empty()) {
       data()->MarkAllocated(mode(), static_cast<int>(i));
     }
   }
   allocations_.clear();
 
+  TryReuseSpillRangesForGroups();
+
   TRACE("End allocating function %s with the Greedy Allocator\n",
         data()->debug_name());
 }
 
 
+void GreedyAllocator::TryReuseSpillRangesForGroups() {
+  for (TopLevelLiveRange* top : data()->live_ranges()) {
+    if (!CanProcessRange(top) || !top->is_phi() || top->group() == nullptr) {
+      continue;
+    }
+
+    SpillRange* spill_range = nullptr;
+    for (LiveRange* member : top->group()->ranges()) {
+      if (!member->TopLevel()->HasSpillRange()) continue;
+      SpillRange* member_range = member->TopLevel()->GetSpillRange();
+      if (spill_range == nullptr) {
+        spill_range = member_range;
+      } else {
+        // This may not always succeed, because we group non-conflicting ranges
+        // that may have been splintered, and the splinters may cause conflicts
+        // in the spill ranges.
+        // TODO(mtrofin): should the splinters own their own spill ranges?
+        spill_range->TryMerge(member_range);
+      }
+    }
+  }
+}
+
+
 float GreedyAllocator::GetMaximumConflictingWeight(
     unsigned reg_id, const LiveRange* range, float competing_weight) const {
   float ret = LiveRange::kInvalidWeight;
 
   auto conflicts = current_allocations(reg_id)->GetConflicts(range);
   for (LiveRange* conflict = conflicts.Current(); conflict != nullptr;
        conflict = conflicts.GetNext()) {
     DCHECK_NE(conflict->weight(), LiveRange::kInvalidWeight);
     if (competing_weight <= conflict->weight()) return LiveRange::kMaxWeight;
     ret = Max(ret, conflict->weight());
@@ skipping 167 matching lines @@
     scheduler().Schedule(range);
     return;
   }
   SpillRangeAsLastResort(range);
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8