Implement loop variable assignment analysis.

src/compiler/ast-loop-assignment-analyzer.cc

+// Copyright 2014 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/ast-loop-assignment-analyzer.h"
+#include "src/parser.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+typedef class AstLoopAssignmentAnalyzer ALAA;  // for code shortitude.
+
+ALAA::AstLoopAssignmentAnalyzer(Zone* zone, CompilationInfo* info)
+    : info_(info), loop_stack_(zone) {
+  InitializeAstVisitor(zone);
+}
+
+
+LoopAssignmentAnalysis* ALAA::Analyze() {
+  LoopAssignmentAnalysis* a = new (zone()) LoopAssignmentAnalysis(zone());
+  result_ = a;
+  VisitStatements(info()->function()->body());
+  result_ = NULL;
+  return a;
+}
+
+
+void ALAA::Enter(IterationStatement* loop) {
+  int num_variables = 1 + info()->scope()->num_parameters() +
+                      info()->scope()->num_stack_slots();
+  BitVector* bits = new (zone()) BitVector(num_variables, zone());
+  loop_stack_.push_back(bits);
+}
+
+
+void ALAA::Exit(IterationStatement* loop) {
+  DCHECK(loop_stack_.size() > 0);
+  BitVector* bits = loop_stack_.back();
+  loop_stack_.pop_back();
+  if (!loop_stack_.empty()) {
+    loop_stack_.back()->Union(*bits);
+  }
+  result_->list_.push_back(
+      std::pair<IterationStatement*, BitVector*>(loop, bits));
+}
+
+
+// ---------------------------------------------------------------------------
+// -- Leaf nodes -------------------------------------------------------------
+// ---------------------------------------------------------------------------
+
+void ALAA::VisitVariableDeclaration(VariableDeclaration* leaf) {}
+void ALAA::VisitFunctionDeclaration(FunctionDeclaration* leaf) {}
+void ALAA::VisitModuleDeclaration(ModuleDeclaration* leaf) {}
+void ALAA::VisitImportDeclaration(ImportDeclaration* leaf) {}
+void ALAA::VisitExportDeclaration(ExportDeclaration* leaf) {}
+void ALAA::VisitModuleVariable(ModuleVariable* leaf) {}
+void ALAA::VisitModulePath(ModulePath* leaf) {}
+void ALAA::VisitModuleUrl(ModuleUrl* leaf) {}
+void ALAA::VisitEmptyStatement(EmptyStatement* leaf) {}
+void ALAA::VisitContinueStatement(ContinueStatement* leaf) {}
+void ALAA::VisitBreakStatement(BreakStatement* leaf) {}
+void ALAA::VisitDebuggerStatement(DebuggerStatement* leaf) {}
+void ALAA::VisitFunctionLiteral(FunctionLiteral* leaf) {}
+void ALAA::VisitNativeFunctionLiteral(NativeFunctionLiteral* leaf) {}
+void ALAA::VisitVariableProxy(VariableProxy* leaf) {}
+void ALAA::VisitLiteral(Literal* leaf) {}
+void ALAA::VisitRegExpLiteral(RegExpLiteral* leaf) {}
+void ALAA::VisitThisFunction(ThisFunction* leaf) {}
+void ALAA::VisitSuperReference(SuperReference* leaf) {}
+
+
+// ---------------------------------------------------------------------------
+// -- Pass-through nodes------------------------------------------------------
+// ---------------------------------------------------------------------------
+void ALAA::VisitModuleLiteral(ModuleLiteral* e) { Visit(e->body()); }
+
+
+void ALAA::VisitBlock(Block* stmt) { VisitStatements(stmt->statements()); }
+
+
+void ALAA::VisitExpressionStatement(ExpressionStatement* stmt) {
+  Visit(stmt->expression());
+}
+
+
+void ALAA::VisitIfStatement(IfStatement* stmt) {
+  Visit(stmt->condition());
+  Visit(stmt->then_statement());
+  Visit(stmt->else_statement());
+}
+
+
+void ALAA::VisitReturnStatement(ReturnStatement* stmt) {
+  Visit(stmt->expression());
+}
+
+
+void ALAA::VisitWithStatement(WithStatement* stmt) {
+  Visit(stmt->expression());
+  Visit(stmt->statement());
+}
+
+
+void ALAA::VisitSwitchStatement(SwitchStatement* stmt) {
+  Visit(stmt->tag());
+  ZoneList<CaseClause*>* clauses = stmt->cases();
+  for (int i = 0; i < clauses->length(); i++) {
+    Visit(clauses->at(i));
+  }
+}
+
+
+void ALAA::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
+  Visit(stmt->try_block());
+  Visit(stmt->finally_block());
+}
+
+
+void ALAA::VisitClassLiteral(ClassLiteral* e) {
+  VisitIfNotNull(e->extends());
+  VisitIfNotNull(e->constructor());
+  ZoneList<ObjectLiteralProperty*>* properties = e->properties();
+  for (int i = 0; i < properties->length(); i++) {
+    Visit(properties->at(i)->value());
+  }
+}
+
+
+void ALAA::VisitConditional(Conditional* e) {
+  Visit(e->condition());
+  Visit(e->then_expression());
+  Visit(e->else_expression());
+}
+
+
+void ALAA::VisitObjectLiteral(ObjectLiteral* e) {
+  ZoneList<ObjectLiteralProperty*>* properties = e->properties();
+  for (int i = 0; i < properties->length(); i++) {
+    Visit(properties->at(i)->value());
+  }
+}
+
+
+void ALAA::VisitArrayLiteral(ArrayLiteral* e) { VisitExpressions(e->values()); }
+
+
+void ALAA::VisitYield(Yield* stmt) {
+  Visit(stmt->generator_object());
+  Visit(stmt->expression());
+}
+
+
+void ALAA::VisitThrow(Throw* stmt) { Visit(stmt->exception()); }
+
+
+void ALAA::VisitProperty(Property* e) {
+  Visit(e->obj());
+  Visit(e->key());
+}
+
+
+void ALAA::VisitCall(Call* e) {
+  Visit(e->expression());
+  VisitExpressions(e->arguments());
+}
+
+
+void ALAA::VisitCallNew(CallNew* e) {
+  Visit(e->expression());
+  VisitExpressions(e->arguments());
+}
+
+
+void ALAA::VisitCallRuntime(CallRuntime* e) {
+  VisitExpressions(e->arguments());
+}
+
+
+void ALAA::VisitUnaryOperation(UnaryOperation* e) { Visit(e->expression()); }
+
+
+void ALAA::VisitBinaryOperation(BinaryOperation* e) {
+  Visit(e->left());
+  Visit(e->right());
+}
+
+
+void ALAA::VisitCompareOperation(CompareOperation* e) {
+  Visit(e->left());
+  Visit(e->right());
+}
+
+
+void ALAA::VisitCaseClause(CaseClause* cc) {
+  if (!cc->is_default()) Visit(cc->label());
+  VisitStatements(cc->statements());
+}
+
+
+// ---------------------------------------------------------------------------
+// -- Interesting nodes-------------------------------------------------------
+// ---------------------------------------------------------------------------
+void ALAA::VisitModuleStatement(ModuleStatement* stmt) {
+  Visit(stmt->body());
+  // TODO(turbofan): can a module appear in a loop?
+  AnalyzeAssignment(stmt->proxy()->var());
+}
+
+
+void ALAA::VisitTryCatchStatement(TryCatchStatement* stmt) {
+  Visit(stmt->try_block());
+  Visit(stmt->catch_block());
+  // TODO(turbofan): are catch variables well-scoped?
+  AnalyzeAssignment(stmt->variable());
+}
+
+
+void ALAA::VisitDoWhileStatement(DoWhileStatement* loop) {
+  Enter(loop);
+  Visit(loop->body());
+  Visit(loop->cond());
+  Exit(loop);
+}
+
+
+void ALAA::VisitWhileStatement(WhileStatement* loop) {
+  Enter(loop);
+  Visit(loop->cond());
+  Visit(loop->body());
+  Exit(loop);
+}
+
+
+void ALAA::VisitForStatement(ForStatement* loop) {
+  VisitIfNotNull(loop->init());
+  Enter(loop);
+  VisitIfNotNull(loop->cond());
+  Visit(loop->body());
+  VisitIfNotNull(loop->next());
+  Exit(loop);
+}
+
+
+void ALAA::VisitForInStatement(ForInStatement* loop) {
+  Enter(loop);
+  Visit(loop->each());
+  Visit(loop->subject());
+  Visit(loop->body());
+  Exit(loop);
+}
+
+
+void ALAA::VisitForOfStatement(ForOfStatement* loop) {
+  Enter(loop);
+  Visit(loop->each());
+  Visit(loop->subject());
+  Visit(loop->body());
+  Exit(loop);
+}
+
+
+void ALAA::VisitAssignment(Assignment* stmt) {
+  Expression* l = stmt->target();
+  Visit(l);
+  Visit(stmt->value());
+  if (l->IsVariableProxy()) AnalyzeAssignment(l->AsVariableProxy()->var());
+}
+
+
+void ALAA::VisitCountOperation(CountOperation* e) {
+  Expression* l = e->expression();
+  Visit(l);
+  if (l->IsVariableProxy()) AnalyzeAssignment(l->AsVariableProxy()->var());
+}
+
+
+void ALAA::AnalyzeAssignment(Variable* var) {
+  if (!loop_stack_.empty() && var->IsStackAllocated()) {
+    loop_stack_.back()->Add(GetVariableIndex(info()->scope(), var));
+  }
+}
+
+
+int ALAA::GetVariableIndex(Scope* scope, Variable* var) {
+  CHECK(var->IsStackAllocated());
+  if (var->is_this()) return 0;
+  if (var->IsParameter()) return 1 + var->index();
+  return 1 + scope->num_parameters() + var->index();
+}
+
+
+int LoopAssignmentAnalysis::GetAssignmentCountForTesting(Scope* scope,
+                                                         Variable* var) {
+  int count = 0;
+  int var_index = AstLoopAssignmentAnalyzer::GetVariableIndex(scope, var);
+  for (size_t i = 0; i < list_.size(); i++) {
+    if (list_[i].second->Contains(var_index)) count++;
+  }
+  return count;
+}
+}
+}
+}  // namespace v8::internal::compiler