Collect type information based on stack allocated values for OSR.

src/typing.cc

Index: src/typing.cc
diff --git a/src/typing.cc b/src/typing.cc
index 9458d6dc2fe401142f7b4e3392cea419fe94500c..6c14295911e08d30c8ba6f1b14ec2516e0bf0a4f 100644
--- a/src/typing.cc
+++ b/src/typing.cc
@@ -27,6 +27,8 @@
 
 #include "typing.h"
 
+#include "frames.h"
+#include "frames-inl.h"
 #include "parser.h"  // for CompileTimeValue; TODO(rossberg): should move
 #include "scopes.h"
 
@@ -41,8 +43,11 @@ AstTyper::AstTyper(CompilationInfo* info)
           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.

 }
 
 
@@ -68,6 +73,77 @@ void AstTyper::Run(CompilationInfo* info) {
 
 #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());     \
@@ -339,6 +415,7 @@ 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));
   }
 }