Basic interface inference for modules.

src/interface.cc

Index: src/interface.cc
diff --git a/src/interface.cc b/src/interface.cc
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+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "interface.h"
+
+namespace v8 {
+namespace internal {
+
+static bool Match(void* key1, void* key2) {
+  String* name1 = *static_cast<String**>(key1);
+  String* name2 = *static_cast<String**>(key2);
+  ASSERT(name1->IsSymbol());
+  ASSERT(name2->IsSymbol());
+  return name1 == name2;
+}
+
+
+Interface* Interface::Lookup(Handle<String> name) {
+  ASSERT(IsModule());
+  ZoneHashMap* map = Chase()->exports_;
+  if (map == NULL) return NULL;
+  ZoneHashMap::Entry* p = map->Lookup(name.location(), name->Hash(), false);

[Sven Panne, 2012/03/08 08:55:00]

Hash relies on the actual String contents, while Match relies on pointer
identity. Therefore Hash is a bit of overkill, you could hash the pointer value.
But I am not sure how performance-critical this is, so I leave this up to you.

[rossberg, 2012/03/08 10:47:06]

I pretty much copied this bit from the code in scopes.cc. Also, we might
eventually need to make interfaces persistent across compiles, so view it as a
partial preparation for that. :)

+  if (p == NULL) return NULL;
+  ASSERT(*static_cast<String**>(p->key) == *name);
+  ASSERT(p->value != NULL);
+  return static_cast<Interface*>(p->value);
+}
+
+
+#ifdef DEBUG
+// Current nesting depth for debug output.
+class Nesting {
+ public:
+  Nesting()  { current_ += 2; }
+  ~Nesting() { current_ -= 2; }
+  static int current() { return current_; }
+ private:
+  static int current_;
+};
+
+int Nesting::current_ = 0;
+#endif
+
+
+void Interface::DoAdd(
+    void* name, uint32_t hash, Interface* interface, bool* ok) {
+  MakeModule(ok);
+  if (!*ok) return;
+
+#ifdef DEBUG
+  if (FLAG_print_interface_details) {
+    PrintF("%*s# Adding...\n", Nesting::current(), "");
+    PrintF("%*sthis = ", Nesting::current(), "");
+    this->Print(Nesting::current());
+    PrintF("%*s%s : ", Nesting::current(), "",
+           (*reinterpret_cast<String**>(name))->ToAsciiArray());
+    interface->Print(Nesting::current());
+  }
+#endif
+
+  ZoneHashMap** map = &Chase()->exports_;
+  if (*map == NULL) *map = new ZoneHashMap(Match, 8);
+
+  ZoneHashMap::Entry* p = (*map)->Lookup(name, hash, !IsFrozen());
+  if (p == NULL) {
+    // This didn't have name but was frozen already, that's an error.
+    *ok = false;
+  } else if (p->value == NULL) {
+    p->value = interface;
+  } else {
+#ifdef DEBUG
+    Nesting nested;
+#endif
+    reinterpret_cast<Interface*>(p->value)->Unify(interface, ok);
+  }
+
+#ifdef DEBUG
+  if (FLAG_print_interface_details) {
+    PrintF("%*sthis' = ", Nesting::current(), "");
+    this->Print(Nesting::current());
+    PrintF("%*s# Added.\n", Nesting::current(), "");
+  }
+#endif
+}
+
+
+void Interface::Unify(Interface* that, bool* ok) {
+  if (this->forward_) return this->Chase()->Unify(that, ok);
+  if (that->forward_) return this->Unify(that->Chase(), ok);
+  ASSERT(this->forward_ == NULL);
+  ASSERT(that->forward_ == NULL);
+
+  *ok = true;
+  if (this == that) return;
+  if (this->IsValue()) return that->MakeValue(ok);
+  if (that->IsValue()) return this->MakeValue(ok);
+
+#ifdef DEBUG
+  if (FLAG_print_interface_details) {
+    PrintF("%*s# Unifying...\n", Nesting::current(), "");
+    PrintF("%*sthis = ", Nesting::current(), "");
+    this->Print(Nesting::current());
+    PrintF("%*sthat = ", Nesting::current(), "");
+    that->Print(Nesting::current());
+  }
+#endif
+
+  // Merge the smaller interface into the larger, for performance.
+  if (this->exports_ != NULL && (that->exports_ == NULL ||
+      this->exports_->occupancy() >= that->exports_->occupancy())) {
+    this->DoUnify(that, ok);
+  } else {
+    that->DoUnify(this, ok);
+  }
+
+#ifdef DEBUG
+  if (FLAG_print_interface_details) {
+    PrintF("%*sthis' = ", Nesting::current(), "");
+    this->Print(Nesting::current());
+    PrintF("%*sthat' = ", Nesting::current(), "");
+    that->Print(Nesting::current());
+    PrintF("%*s# Unified.\n", Nesting::current(), "");
+  }
+#endif
+}
+
+
+void Interface::DoUnify(Interface* that, bool* ok) {
+  ASSERT(this->forward_ == NULL);
+  ASSERT(that->forward_ == NULL);
+  ASSERT(!this->IsValue());
+  ASSERT(!that->IsValue());
+  ASSERT(*ok);
+
+#ifdef DEBUG
+    Nesting nested;
+#endif
+
+  // Try to merge all members from that into this.
+  ZoneHashMap* map = that->exports_;
+  if (map != NULL) {
+    for (ZoneHashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
+      this->DoAdd(p->key, p->hash, static_cast<Interface*>(p->value), ok);

[Sven Panne, 2012/03/08 08:55:00]

If I see this correctly, this recursion is potentially bounded only by the
structure of the input. Although this won't be a problem in practice, I think we
will have to add a guard against pathological cases (or attacks).

[rossberg, 2012/03/08 10:47:06]

The depth of module types is linearly bounded by the size of the program.
Realistically, it is more likely that the stack is first blown by the parser,
which does not protect against that event either AFAICS. So I don't think it's
currently worth doing here.

+      if (!*ok) return;
+    }
+  }
+
+  // If the new interface is larger than that's, then there were members in
+  // 'this' which 'that' didn't have. If 'that' was frozen that is an error.
+  int this_size = this->exports_ == NULL ? 0 : this->exports_->occupancy();
+  int that_size = map == NULL ? 0 : map->occupancy();
+  if (that->IsFrozen() && this_size > that_size) {
+    *ok = false;
+    return;
+  }
+
+  // Merge interfaces.
+  this->flags_ |= that->flags_;
+  that->forward_ = this;
+}
+
+
+#ifdef DEBUG
+void Interface::Print(int n) {
+  int n0 = n > 0 ? n : 0;
+
+  if (FLAG_print_interface_details) {
+    PrintF("%p", static_cast<void*>(this));
+    for (Interface* link = this->forward_; link != NULL; link = link->forward_)
+      PrintF("->%p", static_cast<void*>(link));
+    PrintF(" ");
+  }
+
+  if (IsUndetermined()) {
+    PrintF("undetermined\n");
+  } else if (IsValue()) {
+    PrintF("value\n");
+  } else if (IsModule()) {
+    PrintF("module %s{", IsFrozen() ? "" : "(unresolved) ");
+    ZoneHashMap* map = Chase()->exports_;
+    if (map == NULL || map->occupancy() == 0) {
+      PrintF("}\n");
+    } else if (n < 0 || n0 >= 2 * FLAG_print_interface_depth) {
+      // Avoid infinite recursion on cyclic types.
+      PrintF("...}\n");
+    } else {
+      PrintF("\n");
+      for (ZoneHashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
+        String* name = *static_cast<String**>(p->key);
+        Interface* interface = static_cast<Interface*>(p->value);
+        PrintF("%*s%s : ", n0 + 2, "", name->ToAsciiArray());
+        interface->Print(n0 + 2);
+      }
+      PrintF("%*s}\n", n0, "");
+    }
+  }
+}
+#endif
+
+} }  // namespace v8::internal