[turbofan] optimize spills in defered blocks

Up to now, for ranges spilled in deferred blocks, we would spill every
time a range would switch from using a register to spill slots. That can
be redundant, leading to avoidable code size  cost.

This change addresses this issue, by performing the spills as early as
possible.

BUG=

Review URL: https://codereview.chromium.org/1551013002

Cr-Commit-Position: refs/heads/master@{#33413}

src/compiler/live-range-separator.cc

@@ -119,6 +119,7 @@ void LiveRangeSeparator::Splinter() {
 
 
 void LiveRangeMerger::MarkRangesSpilledInDeferredBlocks() {
+  const InstructionSequence *code = data()->code();
   for (TopLevelLiveRange *top : data()->live_ranges()) {
     if (top == nullptr || top->IsEmpty() || top->splinter() == nullptr ||
         top->HasSpillOperand() || !top->splinter()->HasSpillRange()) {
@@ -132,7 +133,10 @@ void LiveRangeMerger::MarkRangesSpilledInDeferredBlocks() {
         break;
       }
     }
-    if (child == nullptr) top->MarkSpilledInDeferredBlock();
+    if (child == nullptr) {
+      top->TreatAsSpilledInDeferredBlock(data()->allocation_zone(),
+                                         code->InstructionBlockCount());
+    }
   }
 }
 

src/compiler/register-allocator.h

@@ -579,14 +579,17 @@ class TopLevelLiveRange final : public LiveRange {
   // and instead let the LiveRangeConnector perform the spills within the
   // deferred blocks. If so, we insert here spills for non-spilled ranges
   // with slot use positions.
-  void MarkSpilledInDeferredBlock() {
+  void TreatAsSpilledInDeferredBlock(Zone* zone, int total_block_count) {
     spill_start_index_ = -1;
     spilled_in_deferred_blocks_ = true;
     spill_move_insertion_locations_ = nullptr;
+    list_of_blocks_requiring_spill_operands_ =
+        new (zone) BitVector(total_block_count, zone);
   }
 
-  bool TryCommitSpillInDeferredBlock(InstructionSequence* code,
-                                     const InstructionOperand& spill_operand);
+  void CommitSpillInDeferredBlocks(RegisterAllocationData* data,
+                                   const InstructionOperand& spill_operand,
+                                   BitVector* necessary_spill_points);
 
   TopLevelLiveRange* splintered_from() const { return splintered_from_; }
   bool IsSplinter() const { return splintered_from_ != nullptr; }
@@ -617,7 +620,8 @@ class TopLevelLiveRange final : public LiveRange {
 
   struct SpillMoveInsertionList;
 
-  SpillMoveInsertionList* spill_move_insertion_locations() const {
+  SpillMoveInsertionList* GetSpillMoveInsertionLocations() const {
+    DCHECK(!IsSpilledOnlyInDeferredBlocks());
     return spill_move_insertion_locations_;
   }
   TopLevelLiveRange* splinter() const { return splinter_; }
@@ -634,6 +638,16 @@ class TopLevelLiveRange final : public LiveRange {
   void MarkHasPreassignedSlot() { has_preassigned_slot_ = true; }
   bool has_preassigned_slot() const { return has_preassigned_slot_; }
 
+  void AddBlockRequiringSpillOperand(RpoNumber block_id) {
+    DCHECK(IsSpilledOnlyInDeferredBlocks());
+    GetListOfBlocksRequiringSpillOperands()->Add(block_id.ToInt());
+  }
+
+  BitVector* GetListOfBlocksRequiringSpillOperands() const {
+    DCHECK(IsSpilledOnlyInDeferredBlocks());
+    return list_of_blocks_requiring_spill_operands_;
+  }
+
  private:
   void SetSplinteredFrom(TopLevelLiveRange* splinter_parent);
 
@@ -650,7 +664,12 @@ class TopLevelLiveRange final : public LiveRange {
     InstructionOperand* spill_operand_;
     SpillRange* spill_range_;
   };
-  SpillMoveInsertionList* spill_move_insertion_locations_;
+
+  union {
+    SpillMoveInsertionList* spill_move_insertion_locations_;
+    BitVector* list_of_blocks_requiring_spill_operands_;
+  };
+
   // TODO(mtrofin): generalize spilling after definition, currently specialized
   // just for spill in a single deferred block.
   bool spilled_in_deferred_blocks_;
@@ -1125,6 +1144,7 @@ class ReferenceMapPopulator final : public ZoneObject {
 };
 
 
+class LiveRangeBoundArray;
 // Insert moves of the form
 //
 //          Operand(child_(k+1)) = Operand(child_k)
@@ -1157,6 +1177,10 @@ class LiveRangeConnector final : public ZoneObject {
                          const InstructionBlock* pred,
                          const InstructionOperand& pred_op);
 
+  void CommitSpillsInDeferredBlocks(TopLevelLiveRange* range,
+                                    LiveRangeBoundArray* array,
+                                    Zone* temp_zone);
+
   RegisterAllocationData* const data_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRangeConnector);