Remove per-isolate compile-time constants cache.

runtime/vm/parser.h

Index: runtime/vm/parser.h
diff --git a/runtime/vm/parser.h b/runtime/vm/parser.h
index 7798edb2cbcbe2c094d71e7298a7f91368affe17..e29f86e05a78aa50a544f8c1e51c22ab419558a6 100644
--- a/runtime/vm/parser.h
+++ b/runtime/vm/parser.h
@@ -44,81 +44,10 @@ class RecursionChecker;
 // background compilation, we are not able to evaluate the constants
 // so this cache is necessary to support background compilation.
 //
-// There are two places a constant can be cached, depending on whether
-// the script is in the vm heap (snapshot) or not.
-//
-// When a script is in the vm heap, we are not able to cache the
-// constants on the script itself (it is read-only) so we cache them
-// in a per-isolate shared map in the object store.  In this case the
-// map key is a pair (array) with 2 elements:
-//
-// - key[0] contains the canonicalized url of the script.
-// - key[1] contains the token position of the constant in the script.
-//
-// The VMConstantsMap type is used to implement this per-isolate map.
-//
-// When a script is not in the vm heap, we cache the constants with
-// the script itself.  This is helpful during isolate reloading, as it
-// allows us to reference the compile time constants associated with a
-// particular version of a script.  In this case the map key is simply
-// the TokenPosition where the constant is defined.
-//
-// The ConstantsMap type is used to implement this per-script map.
-
-// The key for the per-isolate compile time constants map.  By using a
-// ValueObject we are able to look up a constant without allocating a
-// key pair (array).
-// The per-script compile-time constants map.
-struct UrlAndPosKey : ValueObject {
-  UrlAndPosKey(const String& url, TokenPosition pos)
-      : script_url(url), token_pos(pos) { }
-  const String& script_url;
-  TokenPosition token_pos;
-};
-
-// The per-isolate compile-time constants map.
-class VMConstMapKeyEqualsTraits {
- public:
-  static const char* Name() { return "VMConstMapKeyEqualsTraits"; }
-  static bool ReportStats() { return false; }
-
-  static bool IsMatch(const Object& a, const Object& b) {
-    const Array& key1 = Array::Cast(a);
-    const Array& key2 = Array::Cast(b);
-    // Compare raw strings of script url symbol and raw smi of token positon.
-    return (key1.At(0) == key2.At(0)) && (key1.At(1) == key2.At(1));
-  }
-  static bool IsMatch(const UrlAndPosKey& key1, const Object& b) {
-    const Array& key2 = Array::Cast(b);
-    // Compare raw strings of script url symbol and token positon.
-    return (key1.script_url.raw() == key2.At(0))
-        && (key1.token_pos.value() == Smi::Value(Smi::RawCast(key2.At(1))));
-  }
-  static uword Hash(const Object& obj) {
-    const Array& key = Array::Cast(obj);
-    intptr_t url_hash = String::HashRawSymbol(String::RawCast(key.At(0)));
-    intptr_t pos = Smi::Value(Smi::RawCast(key.At(1)));
-    return HashValue(url_hash, pos);
-  }
-  static uword Hash(const UrlAndPosKey& key) {
-    return HashValue(String::HashRawSymbol(key.script_url.raw()),
-                     key.token_pos.value());
-  }
-  // Used by CacheConstantValue if a new constant is added to the map.
-  static RawObject* NewKey(const UrlAndPosKey& key) {
-    const Array& key_obj = Array::Handle(Array::New(2));
-    key_obj.SetAt(0, key.script_url);
-    key_obj.SetAt(1, Smi::Handle(Smi::New(key.token_pos.value())));
-    return key_obj.raw();;
-  }
-
- private:
-  static uword HashValue(intptr_t url_hash, intptr_t pos) {
-    return url_hash * pos % (Smi::kMaxValue - 13);
-  }
-};
-typedef UnorderedHashMap<VMConstMapKeyEqualsTraits> VMConstantsMap;
-
+// We cache the constants with the script itself. This is helpful during isolate
+// reloading, as it allows us to reference the compile time constants associated
+// with a particular version of a script. The map key is simply the
+// TokenPosition where the constant is defined.
 class ConstMapKeyEqualsTraits {
  public:
   static const char* Name() { return "ConstMapKeyEqualsTraits"; }