Collect type information based on stack allocated values for OSR.

src/typing.cc

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 #include "typing.h"
 
+#include "frames.h"
+#include "frames-inl.h"
 #include "parser.h"  // for CompileTimeValue; TODO(rossberg): should move
 #include "scopes.h"
 
 namespace v8 {
 namespace internal {
 
 
 AstTyper::AstTyper(CompilationInfo* info)
     : info_(info),
       oracle_(
           Handle<Code>(info->closure()->shared()->code()),
           Handle<Context>(info->closure()->context()->native_context()),
           info->isolate(),
           info->zone()),
-      store_(info->zone()) {
+      store_(info->zone()),
+      parameter_types_(NULL),
+      stack_local_types_(NULL) {
   InitializeAstVisitor(info->isolate());
+  if (info_->is_osr()) ObserveTypesOnStack();

[rossberg, 2013/12/16 09:57:26]

This should go into the Run method. It is not constructing the visitor, it is
part of collecting the type information.

More importantly, as discussed offline, I think the approach in this CL is not
right for two reasons:

(1) It is not sound. It assumes that the stack types can never change.

(2) It duplicates the store typing.

These two problems are related. To fix them, instead of having separate lists,
you should refine the existing store with the type information from the stack
values -- at the point where the code would continue after OSR (i.e., before
loop bodies with the respective OSR AST id?). The refinement should be
expressible by an Alt effect, I think.

 }
 
 
 #define RECURSE(call)                         \
   do {                                        \
     ASSERT(!visitor->HasStackOverflow());     \
     call;                                     \
     if (visitor->HasStackOverflow()) return;  \
   } while (false)
 
 void AstTyper::Run(CompilationInfo* info) {
   AstTyper* visitor = new(info->zone()) AstTyper(info);
   Scope* scope = info->scope();
 
   // Handle implicit declaration of the function name in named function
   // expressions before other declarations.
   if (scope->is_function_scope() && scope->function() != NULL) {
     RECURSE(visitor->VisitVariableDeclaration(scope->function()));
   }
   RECURSE(visitor->VisitDeclarations(scope->declarations()));
   RECURSE(visitor->VisitStatements(info->function()->body()));
 }
 
 #undef RECURSE
 
+
+Handle<Type> AstTyper::ObserveType(Object* value) {
+  if (value->IsUndefined() || value->IsTheHole()) {

[rossberg, 2013/12/16 09:57:26]

Why is the type None for undefined?

+    return Handle<Type>(Type::None(), isolate());
+  } else {
+    return Handle<Type>(Type::OfCurrently(Handle<Object>(value, isolate())),
+                        isolate());
+  }
+}
+
+
+void AstTyper::ObserveTypesOnStack() {
+  DisallowHeapAllocation no_gc;
+  JavaScriptFrameIterator it(isolate());
+  JavaScriptFrame* frame = it.frame();
+  Scope* scope = info_->scope();
+
+  // Assert that the frame on the stack belongs to the function we want to OSR.
+  ASSERT_EQ(*info_->closure(), frame->function());
+
+  int params = scope->num_parameters();
+  int locals = scope->num_stack_slots();
+
+  parameter_types_ = new(zone()) ZoneList<Handle<Type> >(params + 1, zone());
+  stack_local_types_ = new(zone()) ZoneList<Handle<Type> >(locals, zone());
+
+  // The receiver ('this') is a parameter with index -1.  We store it as
+  // element 0 and shift other params up by 1.
+  parameter_types_->Add(ObserveType(frame->receiver()), zone());
+  for (int i = 0; i < params; i++) {
+    parameter_types_->Add(ObserveType(frame->GetParameter(i)), zone());
+  }
+
+  // This includes the function var, if it is stored as a stack local.
+  for (int i = 0; i < locals; i++) {
+    stack_local_types_->Add(ObserveType(frame->GetExpression(i)), zone());
+  }
+}
+
+
+Handle<Type> AstTyper::GetObservedType(Variable* var) {
+  ASSERT(info_->is_osr());
+  ZoneList<Handle<Type> >* list;
+  int index = var->index();
+
+  if (var->IsParameter()) {
+    index += 1;
+    list = parameter_types_;
+  } else {
+    ASSERT(var->IsStackLocal());
+    list = stack_local_types_;
+  }
+
+  // We could also observe the type of context allocated values.  We would go
+  // up the function's scope chain until we find the variable's scope, go up
+  // the context chain at the same time, and load the value from the context
+  // slot stored as variable index.  But this seems not to be worth the effort.
+
+  Handle<Type> result = list->at(index);
+#ifdef OBJECT_PRINT
+  if (FLAG_trace_osr && FLAG_print_scopes) {
+    PrintF("  observed %s : ", var->IsParameter() ? "param" : "local");
+    var->name()->Print();
+    PrintF(" -> ");
+    result->TypePrint();
+  }
+#endif
+  return result;
+}
+
+
 #define RECURSE(call)                \
   do {                               \
     ASSERT(!HasStackOverflow());     \
     call;                            \
     if (HasStackOverflow()) return;  \
   } while (false)
 
 
 void AstTyper::VisitStatements(ZoneList<Statement*>* stmts) {
   for (int i = 0; i < stmts->length(); ++i) {
@@ skipping 251 matching lines @@
   NarrowType(expr, Bounds::Either(
       expr->then_expression()->bounds(),
       expr->else_expression()->bounds(), isolate_));
 }
 
 
 void AstTyper::VisitVariableProxy(VariableProxy* expr) {
   Variable* var = expr->var();
   if (var->IsStackAllocated()) {
     NarrowType(expr, store_.LookupBounds(variable_index(var)));
+    if (info_->is_osr()) NarrowLowerType(expr, GetObservedType(var));
   }
 }
 
 
 void AstTyper::VisitLiteral(Literal* expr) {
   Type* type = Type::Constant(expr->value(), isolate_);
   NarrowType(expr, Bounds(type, isolate_));
 }
 
 
@@ skipping 380 matching lines @@
 void AstTyper::VisitModuleUrl(ModuleUrl* module) {
 }
 
 
 void AstTyper::VisitModuleStatement(ModuleStatement* stmt) {
   RECURSE(Visit(stmt->body()));
 }
 
 
 } }  // namespace v8::internal