[turbofan] Add and use bytecode loop assigment analysis

src/compiler/bytecode-graph-builder.cc

Index: src/compiler/bytecode-graph-builder.cc
diff --git a/src/compiler/bytecode-graph-builder.cc b/src/compiler/bytecode-graph-builder.cc
index 12a5d29d21770df1c39b691df66c3654c3f27946..d522419c2155103281491453dad8fd769ef7ccde 100644
--- a/src/compiler/bytecode-graph-builder.cc
+++ b/src/compiler/bytecode-graph-builder.cc
@@ -68,17 +68,16 @@ class BytecodeGraphBuilder::Environment : public ZoneObject {
   Node* Context() const { return context_; }
   void SetContext(Node* new_context) { context_ = new_context; }
 
-  Environment* CopyForConditional();
-  Environment* CopyForLoop();
-  Environment* CopyForOsrEntry();
+  Environment* Copy();
   void Merge(Environment* other);
-  void PrepareForOsrEntry();
 
-  void PrepareForLoopExit(Node* loop);
+  void PrepareForOsrEntry();
+  void PrepareForLoop(const BytecodeLoopAssignments& assignments);
+  void PrepareForLoopExit(Node* loop,
+                          const BytecodeLoopAssignments& assignments);
 
  private:
   explicit Environment(const Environment* copy);
-  void PrepareForLoop();
 
   bool StateValuesRequireUpdate(Node** state_values, Node** values, int count);
   void UpdateStateValues(Node** state_values, Node** values, int count);
@@ -250,20 +249,7 @@ void BytecodeGraphBuilder::Environment::RecordAfterState(
   }
 }
 
-
-BytecodeGraphBuilder::Environment*
-BytecodeGraphBuilder::Environment::CopyForLoop() {
-  PrepareForLoop();
-  return new (zone()) Environment(this);
-}
-
-BytecodeGraphBuilder::Environment*
-BytecodeGraphBuilder::Environment::CopyForOsrEntry() {
-  return new (zone()) Environment(this);
-}
-
-BytecodeGraphBuilder::Environment*
-BytecodeGraphBuilder::Environment::CopyForConditional() {
+BytecodeGraphBuilder::Environment* BytecodeGraphBuilder::Environment::Copy() {
   return new (zone()) Environment(this);
 }
 
@@ -290,8 +276,8 @@ void BytecodeGraphBuilder::Environment::Merge(
   }
 }
 
-
-void BytecodeGraphBuilder::Environment::PrepareForLoop() {
+void BytecodeGraphBuilder::Environment::PrepareForLoop(
+    const BytecodeLoopAssignments& assignments) {
   // Create a control node for the loop header.
   Node* control = builder()->NewLoop();
 
@@ -299,11 +285,23 @@ void BytecodeGraphBuilder::Environment::PrepareForLoop() {
   Node* effect = builder()->NewEffectPhi(1, GetEffectDependency(), control);
   UpdateEffectDependency(effect);
 
-  // Assume everything in the loop is updated.
+  // Create Phis for any values that may be updated by the end of the loop.
   context_ = builder()->NewPhi(1, context_, control);
-  int size = static_cast<int>(values()->size());
-  for (int i = 0; i < size; i++) {
-    values()->at(i) = builder()->NewPhi(1, values()->at(i), control);
+  for (int i = 0; i < parameter_count(); i++) {
+    if (assignments.ContainsParameter(i)) {
+      values_[i] = builder()->NewPhi(1, values_[i], control);
+    }
+  }
+  for (int i = 0; i < register_count(); i++) {
+    if (assignments.ContainsLocal(i)) {
+      int index = register_base() + i;
+      values_[index] = builder()->NewPhi(1, values_[index], control);
+    }
+  }
+
+  if (assignments.ContainsAccumulator()) {
+    values_[accumulator_base()] =
+        builder()->NewPhi(1, values_[accumulator_base()], control);
   }
 
   // Connect to the loop end.
@@ -368,7 +366,8 @@ bool BytecodeGraphBuilder::Environment::StateValuesRequireUpdate(
   return false;
 }
 
-void BytecodeGraphBuilder::Environment::PrepareForLoopExit(Node* loop) {
+void BytecodeGraphBuilder::Environment::PrepareForLoopExit(
+    Node* loop, const BytecodeLoopAssignments& assignments) {
   DCHECK_EQ(loop->opcode(), IrOpcode::kLoop);
 
   Node* control = GetControlDependency();
@@ -382,15 +381,30 @@ void BytecodeGraphBuilder::Environment::PrepareForLoopExit(Node* loop) {
                                          GetEffectDependency(), loop_exit);
   UpdateEffectDependency(effect_rename);
 
-  // TODO(jarin) We should also rename context here. However, uncoditional
+  // TODO(jarin) We should also rename context here. However, unconditional
   // renaming confuses global object and native context specialization.
   // We should only rename if the context is assigned in the loop.
 
-  // Rename the environmnent values.
-  for (size_t i = 0; i < values_.size(); i++) {
-    Node* rename =
-        graph()->NewNode(common()->LoopExitValue(), values_[i], loop_exit);
-    values_[i] = rename;
+  // Rename the environment values if they were assigned in the loop.
+  for (int i = 0; i < parameter_count(); i++) {
+    if (assignments.ContainsParameter(i)) {
+      Node* rename =
+          graph()->NewNode(common()->LoopExitValue(), values_[i], loop_exit);
+      values_[i] = rename;
+    }
+  }
+  for (int i = 0; i < register_count(); i++) {
+    if (assignments.ContainsLocal(i)) {
+      Node* rename = graph()->NewNode(common()->LoopExitValue(),
+                                      values_[register_base() + i], loop_exit);
+      values_[register_base() + i] = rename;
+    }
+  }
+
+  if (assignments.ContainsAccumulator()) {
+    Node* rename = graph()->NewNode(common()->LoopExitValue(),
+                                    values_[accumulator_base()], loop_exit);
+    values_[accumulator_base()] = rename;
   }
 }
 
@@ -605,7 +619,7 @@ void BytecodeGraphBuilder::PrepareFrameState(Node* node,
 void BytecodeGraphBuilder::VisitBytecodes(bool stack_check) {
   BytecodeAnalysis bytecode_analysis(bytecode_array(), local_zone(),
                                      FLAG_analyze_environment_liveness);
-  bytecode_analysis.Analyze();
+  bytecode_analysis.Analyze(osr_ast_id_);
   set_bytecode_analysis(&bytecode_analysis);
 
   interpreter::BytecodeArrayIterator iterator(bytecode_array());
@@ -628,7 +642,6 @@ void BytecodeGraphBuilder::VisitBytecodes(bool stack_check) {
     SwitchToMergeEnvironment(current_offset);
     if (environment() != nullptr) {
       BuildLoopHeaderEnvironment(current_offset);
-      BuildOSRLoopEntryPoint(current_offset);
 
       // Skip the first stack check if stack_check is false
       if (!stack_check &&
@@ -855,7 +868,7 @@ BytecodeGraphBuilder::Environment* BytecodeGraphBuilder::CheckContextExtensions(
                 extension_slot, jsgraph()->TheHoleConstant());
 
     NewBranch(check_no_extension);
-    Environment* true_environment = environment()->CopyForConditional();
+    Environment* true_environment = environment()->Copy();
 
     {
       NewIfFalse();
@@ -1901,9 +1914,17 @@ void BytecodeGraphBuilder::SwitchToMergeEnvironment(int current_offset) {
 
 void BytecodeGraphBuilder::BuildLoopHeaderEnvironment(int current_offset) {
   if (bytecode_analysis()->IsLoopHeader(current_offset)) {
-    // Add loop header and store a copy so we can connect merged back
-    // edge inputs to the loop header.
-    merge_environments_[current_offset] = environment()->CopyForLoop();
+    const LoopInfo& loop_info =
+        bytecode_analysis()->GetLoopInfoFor(current_offset);
+
+    // Add loop header.
+    environment()->PrepareForLoop(loop_info.assignments());
+
+    BuildOSRLoopEntryPoint(current_offset);
+
+    // Store a copy of the environment so we can connect merged back edge inputs
+    // to the loop header.
+    merge_environments_[current_offset] = environment()->Copy();
   }
 }
 
@@ -1929,13 +1950,14 @@ void BytecodeGraphBuilder::MergeControlToLeaveFunction(Node* exit) {
 }
 
 void BytecodeGraphBuilder::BuildOSRLoopEntryPoint(int current_offset) {
+  DCHECK(bytecode_analysis()->IsLoopHeader(current_offset));
+
   if (!osr_ast_id_.IsNone() && osr_loop_offset_ == current_offset) {
     // For OSR add a special {OsrLoopEntry} node into the current loop header.
     // It will be turned into a usable entry by the OSR deconstruction.
-    Environment* loop_env = merge_environments_[current_offset];
-    Environment* osr_env = loop_env->CopyForOsrEntry();
+    Environment* osr_env = environment()->Copy();
     osr_env->PrepareForOsrEntry();
-    loop_env->Merge(osr_env);
+    environment()->Merge(osr_env);
   }
 }
 
@@ -1966,8 +1988,10 @@ void BytecodeGraphBuilder::BuildLoopExitsUntilLoop(int loop_offset) {
   int current_loop = bytecode_analysis()->GetLoopOffsetFor(origin_offset);
   while (loop_offset < current_loop) {
     Node* loop_node = merge_environments_[current_loop]->GetControlDependency();
-    environment()->PrepareForLoopExit(loop_node);
-    current_loop = bytecode_analysis()->GetParentLoopFor(current_loop);
+    const LoopInfo& loop_info =
+        bytecode_analysis()->GetLoopInfoFor(current_loop);
+    environment()->PrepareForLoopExit(loop_node, loop_info.assignments());
+    current_loop = loop_info.parent_offset();
   }
 }
 
@@ -1981,7 +2005,7 @@ void BytecodeGraphBuilder::BuildJump() {
 
 void BytecodeGraphBuilder::BuildJumpIf(Node* condition) {
   NewBranch(condition);
-  Environment* if_false_environment = environment()->CopyForConditional();
+  Environment* if_false_environment = environment()->Copy();
   NewIfTrue();
   MergeIntoSuccessorEnvironment(bytecode_iterator().GetJumpTargetOffset());
   set_environment(if_false_environment);
@@ -1990,7 +2014,7 @@ void BytecodeGraphBuilder::BuildJumpIf(Node* condition) {
 
 void BytecodeGraphBuilder::BuildJumpIfNot(Node* condition) {
   NewBranch(condition);
-  Environment* if_true_environment = environment()->CopyForConditional();
+  Environment* if_true_environment = environment()->Copy();
   NewIfFalse();
   MergeIntoSuccessorEnvironment(bytecode_iterator().GetJumpTargetOffset());
   set_environment(if_true_environment);
@@ -2128,7 +2152,7 @@ Node* BytecodeGraphBuilder::MakeNode(const Operator* op, int value_input_count,
       int handler_offset = exception_handlers_.top().handler_offset_;
       int context_index = exception_handlers_.top().context_register_;
       interpreter::Register context_register(context_index);
-      Environment* success_env = environment()->CopyForConditional();
+      Environment* success_env = environment()->Copy();
       const Operator* op = common()->IfException();
       Node* effect = environment()->GetEffectDependency();
       Node* on_exception = graph()->NewNode(op, effect, result);