[turbofan] Splinter when range ends at hot block start

We were sometimes losing a splintering opportunity when a range was
ending at the beginning of a hot (==non-deferred) block, when giving
its value to some fixed range - i.e. a fixed operand of the first instruction
in that hot block.

Renamed 2 APIs to better reflect what their intent is.

Added self-checking when introducing moves connecting ranges, to
ensure we don't spill/fill in hot blocks ranges spilled only in deferred
blocks. Verified locally that these checks would have tripped in a few
cases before this change.

BUG=

Review URL: https://codereview.chromium.org/1564583002

Cr-Commit-Position: refs/heads/master@{#33301}

src/compiler/instruction.h

@@ -64,6 +64,7 @@ class InstructionOperand {
   INSTRUCTION_OPERAND_PREDICATE(Allocated, ALLOCATED)
 #undef INSTRUCTION_OPERAND_PREDICATE
 
+  inline bool IsAnyRegister() const;
   inline bool IsRegister() const;
   inline bool IsDoubleRegister() const;
   inline bool IsStackSlot() const;
@@ -504,17 +505,20 @@ class AllocatedOperand : public LocationOperand {
 #undef INSTRUCTION_OPERAND_CASTS
 
 
-bool InstructionOperand::IsRegister() const {
+bool InstructionOperand::IsAnyRegister() const {
   return (IsAllocated() || IsExplicit()) &&
          LocationOperand::cast(this)->location_kind() ==
-             LocationOperand::REGISTER &&
+             LocationOperand::REGISTER;
+}
+
+
+bool InstructionOperand::IsRegister() const {
+  return IsAnyRegister() &&
          !IsFloatingPoint(LocationOperand::cast(this)->representation());
 }
 
 bool InstructionOperand::IsDoubleRegister() const {
-  return (IsAllocated() || IsExplicit()) &&
-         LocationOperand::cast(this)->location_kind() ==
-             LocationOperand::REGISTER &&
+  return IsAnyRegister() &&
          IsFloatingPoint(LocationOperand::cast(this)->representation());
 }
 

src/compiler/live-range-separator.cc

@@ -69,9 +69,9 @@ void SplinterLiveRange(TopLevelLiveRange *range, RegisterAllocationData *data) {
   while (interval != nullptr) {
     UseInterval *next_interval = interval->next();
     const InstructionBlock *first_block =
-        code->GetInstructionBlock(interval->FirstInstructionIndex());
+        code->GetInstructionBlock(interval->FirstGapIndex());
     const InstructionBlock *last_block =
-        code->GetInstructionBlock(interval->LastInstructionIndex());
+        code->GetInstructionBlock(interval->LastGapIndex());
     int first_block_nr = first_block->rpo_number().ToInt();
     int last_block_nr = last_block->rpo_number().ToInt();
     for (int block_id = first_block_nr; block_id <= last_block_nr; ++block_id) {
@@ -110,7 +110,7 @@ void LiveRangeSeparator::Splinter() {
     if (range == nullptr || range->IsEmpty() || range->IsSplinter()) {
       continue;
     }
-    int first_instr = range->first_interval()->FirstInstructionIndex();
+    int first_instr = range->first_interval()->FirstGapIndex();
     if (!data()->code()->GetInstructionBlock(first_instr)->IsDeferred()) {
       SplinterLiveRange(range, data());
     }

src/compiler/register-allocator.cc

@@ -1426,8 +1426,8 @@ bool RegisterAllocationData::RangesDefinedInDeferredStayInDeferred() {
     }
     for (const UseInterval* i = range->first_interval(); i != nullptr;
          i = i->next()) {
-      int first = i->FirstInstructionIndex();
-      int last = i->LastInstructionIndex();
+      int first = i->FirstGapIndex();
+      int last = i->LastGapIndex();
       for (int instr = first; instr <= last;) {
         const InstructionBlock* block = code()->GetInstructionBlock(instr);
         if (!block->IsDeferred()) return false;
@@ -3383,7 +3383,12 @@ void LiveRangeConnector::ResolveControlFlow(Zone* local_zone) {
         InstructionOperand pred_op = result.pred_cover_->GetAssignedOperand();
         InstructionOperand cur_op = result.cur_cover_->GetAssignedOperand();
         if (pred_op.Equals(cur_op)) continue;
-        ResolveControlFlow(block, cur_op, pred_block, pred_op);
+        int move_loc = ResolveControlFlow(block, cur_op, pred_block, pred_op);
+        USE(move_loc);
+        DCHECK_IMPLIES(
+            result.cur_cover_->TopLevel()->IsSpilledOnlyInDeferredBlocks() &&
+                !(pred_op.IsAnyRegister() && cur_op.IsAnyRegister()),
+            code()->GetInstructionBlock(move_loc)->IsDeferred());
       }
       iterator.Advance();
     }
@@ -3391,7 +3396,7 @@ void LiveRangeConnector::ResolveControlFlow(Zone* local_zone) {
 }
 
 
-void LiveRangeConnector::ResolveControlFlow(const InstructionBlock* block,
+int LiveRangeConnector::ResolveControlFlow(const InstructionBlock* block,
                                            const InstructionOperand& cur_op,
                                            const InstructionBlock* pred,
                                            const InstructionOperand& pred_op) {
@@ -3410,6 +3415,7 @@ void LiveRangeConnector::ResolveControlFlow(const InstructionBlock* block,
     position = Instruction::END;
   }
   data()->AddGapMove(gap_index, position, pred_op, cur_op);
+  return gap_index;
 }
 
 
@@ -3446,6 +3452,13 @@ void LiveRangeConnector::ConnectRanges(Zone* local_zone) {
         }
         gap_pos = delay_insertion ? Instruction::END : Instruction::START;
       }
+      // Fills or spills for spilled in deferred blocks ranges must happen
+      // only in deferred blocks.
+      DCHECK_IMPLIES(
+          connect_spilled &&
+              !(prev_operand.IsAnyRegister() && cur_operand.IsAnyRegister()),
+          code()->GetInstructionBlock(gap_index)->IsDeferred());
+
       ParallelMove* move =
           code()->InstructionAt(gap_index)->GetOrCreateParallelMove(
               gap_pos, code_zone());

src/compiler/register-allocator.h

@@ -196,17 +196,19 @@ class UseInterval final : public ZoneObject {
     return start_ <= point && point < end_;
   }
 
-  int FirstInstructionIndex() const {
+  // Returns the index of the first gap covered by this interval.
+  int FirstGapIndex() const {
     int ret = start_.ToInstructionIndex();
-    if (start_.IsInstructionPosition() && start_.IsEnd()) {
+    if (start_.IsInstructionPosition()) {
       ++ret;
     }
     return ret;
   }
 
-  int LastInstructionIndex() const {
+  // Returns the index of the last gap covered by this interval.
+  int LastGapIndex() const {
     int ret = end_.ToInstructionIndex();
-    if (end_.IsGapPosition() || end_.IsStart()) {
+    if (end_.IsGapPosition() && end_.IsStart()) {
       --ret;
     }
     return ret;
@@ -1150,7 +1152,7 @@ class LiveRangeConnector final : public ZoneObject {
 
   bool CanEagerlyResolveControlFlow(const InstructionBlock* block) const;
 
-  void ResolveControlFlow(const InstructionBlock* block,
+  int ResolveControlFlow(const InstructionBlock* block,
                          const InstructionOperand& cur_op,
                          const InstructionBlock* pred,
                          const InstructionOperand& pred_op);