[turbofan] Variable liveness analysis for deopt

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index aa874be5bdff7122b26fb78568d49b8536d6eaf3..da30e14c57b93c9ebd8747317c67eb9e1d094dc0 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -17,6 +17,8 @@ namespace compiler {
 
 class ControlBuilder;
 class Graph;
+class LivenessAnalyzer;
+class LivenessAnalyzerBlock;
 class LoopAssignmentAnalysis;
 class LoopBuilder;
 class Node;
@@ -97,6 +99,9 @@ class AstGraphBuilder : public AstVisitor {
   // Result of loop assignment analysis performed before graph creation.
   LoopAssignmentAnalysis* loop_assignment_analysis_;
 
+  // Analyzer of local variable liveness.
+  LivenessAnalyzer* liveness_analyzer_;
+
   // Growth increment for the temporary buffer used to construct input lists to
   // new nodes.
   static const int kInputBufferSizeIncrement = 64;
@@ -117,6 +122,7 @@ class AstGraphBuilder : public AstVisitor {
   Scope* current_scope() const;
   Node* current_context() const;
   Node* exit_control() const { return exit_control_; }
+  LivenessAnalyzer* liveness_analyzer() { return liveness_analyzer_; }
 
   void set_environment(Environment* env) { environment_ = env; }
   void set_ast_context(AstContext* ctx) { ast_context_ = ctx; }
@@ -262,6 +268,10 @@ class AstGraphBuilder : public AstVisitor {
   // If so, record the stack height into the compilation and return {true}.
   bool CheckOsrEntry(IterationStatement* stmt);
 
+  // Computes local variable liveness and replaces dead variables in
+  // frame states with the undefined values.
+  void RelaxFrameStatesWithLiveness();

[titzer, 2015/02/27 21:09:55]

Can we use another word than "Relax", here and elsewhere? E.g. this method might
be better called "ClearNonLiveFrameStateSlots" or something similar.

+
   // Helper to wrap a Handle<T> into a Unique<T>.
   template <class T>
   Unique<T> MakeUnique(Handle<T> object) {
@@ -347,24 +357,9 @@ class AstGraphBuilder::Environment : public ZoneObject {
 
   // Operations on parameter or local variables. The parameter indices are
   // shifted by 1 (receiver is parameter index -1 but environment index 0).

[Michael Starzinger, 2015/03/02 10:56:34]

nit: I think the second sentence in the comment makes more sense for the
implementation, not the interface. Can we move it to where the magic off-by one
calculation is performed?

[Jarin, 2015/03/16 21:30:12]

Done.

-  void Bind(Variable* variable, Node* node) {
-    DCHECK(variable->IsStackAllocated());
-    if (variable->IsParameter()) {
-      values()->at(variable->index() + 1) = node;
-    } else {
-      DCHECK(variable->IsStackLocal());
-      values()->at(variable->index() + parameters_count_) = node;
-    }
-  }
-  Node* Lookup(Variable* variable) {
-    DCHECK(variable->IsStackAllocated());
-    if (variable->IsParameter()) {
-      return values()->at(variable->index() + 1);
-    } else {
-      DCHECK(variable->IsStackLocal());
-      return values()->at(variable->index() + parameters_count_);
-    }
-  }
+  void Bind(Variable* variable, Node* node);
+  Node* Lookup(Variable* variable);
+  void MakeAllLocalsLive();
 
   Node* Context() const { return contexts_.back(); }
   void PushContext(Node* context) { contexts()->push_back(context); }
@@ -446,7 +441,7 @@ class AstGraphBuilder::Environment : public ZoneObject {
   // Copies this environment at a loop header control-flow point.
   Environment* CopyForLoop(BitVector* assigned, bool is_osr = false) {
     PrepareForLoop(assigned, is_osr);
-    return Copy();
+    return Snapshot();
   }
 
   int ContextStackDepth() { return static_cast<int>(contexts_.size()); }
@@ -455,6 +450,7 @@ class AstGraphBuilder::Environment : public ZoneObject {
   AstGraphBuilder* builder_;
   int parameters_count_;
   int locals_count_;
+  LivenessAnalyzerBlock* liveness_block_;
   NodeVector values_;
   NodeVector contexts_;
   Node* control_dependency_;
@@ -463,8 +459,9 @@ class AstGraphBuilder::Environment : public ZoneObject {
   Node* locals_node_;
   Node* stack_node_;
 
-  explicit Environment(const Environment* copy);
+  explicit Environment(Environment* copy);
   Environment* Copy() { return new (zone()) Environment(this); }
+  Environment* Snapshot();
   void UpdateStateValues(Node** state_values, int offset, int count);
   Zone* zone() const { return builder_->local_zone(); }
   Graph* graph() const { return builder_->graph(); }
@@ -472,6 +469,7 @@ class AstGraphBuilder::Environment : public ZoneObject {
   CommonOperatorBuilder* common() { return builder_->common(); }
   NodeVector* values() { return &values_; }
   NodeVector* contexts() { return &contexts_; }
+  LivenessAnalyzerBlock* liveness_block() { return liveness_block_; }
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);