Bootstrapper.java
package org.mozilla.javascript.optimizer;
import java.lang.invoke.CallSite;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.Arrays;
import java.util.regex.Pattern;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.DynamicLinker;
import jdk.dynalink.DynamicLinkerFactory;
import jdk.dynalink.Operation;
import jdk.dynalink.StandardNamespace;
import jdk.dynalink.StandardOperation;
import jdk.dynalink.linker.support.CompositeTypeBasedGuardingDynamicLinker;
import jdk.dynalink.support.ChainedCallSite;
import org.mozilla.classfile.ByteCode;
import org.mozilla.classfile.ClassFileWriter;
/**
* The Bootstrapper contains the method that is called by invokedynamic instructions in the bytecode
* to map a call site to a method. The "bootstrap" method here is called the first time the runtime
* encounters a particular "invokedynamic" call site, and it is responsible for setting up method
* handles that may be used to invoke code. To learn more about this entire sequence, read up on the
* "jdk.dynalink" package.
*
* <p>We will never go down this entire code path on Android because we do not support bytecode
* generation there.
*/
@SuppressWarnings("AndroidJdkLibsChecker")
public class Bootstrapper {
private static final Pattern SEPARATOR = Pattern.compile(":");
/**
* This is the method handle that's wired in to the bytecode for every dynamic call site in the
* bytecode.
*/
public static final ClassFileWriter.MHandle BOOTSTRAP_HANDLE =
new ClassFileWriter.MHandle(
ByteCode.MH_INVOKESTATIC,
"org.mozilla.javascript.optimizer.Bootstrapper",
"bootstrap",
"(Ljava/lang/invoke/MethodHandles$Lookup;"
+ "Ljava/lang/String;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;");
private static final DynamicLinker linker;
static {
// Set up the linkers that will map each call site to a method handle.
DynamicLinkerFactory factory = new DynamicLinkerFactory();
// Set up a linker that will delegate to other linkers based on the class
// of the first argument to each dynamic invocation. (That's why the method
// signatures in "Signatures" sometimes have different orders than their
// counterparts in "ScriptRuntime".)
// The linker caches the results so that it can efficiently only delegate to
// compatible linkers. It will still go in order, so we put the linkers
// likely to have the biggest impact on performance at the top of the list.
CompositeTypeBasedGuardingDynamicLinker typeLinker =
new CompositeTypeBasedGuardingDynamicLinker(
Arrays.asList(
new ConstAwareLinker(),
new BooleanLinker(),
new IntegerLinker(),
new DoubleLinker(),
new StringLinker(),
new ConsStringLinker(),
new NativeArrayLinker(),
new BaseFunctionLinker()));
// Add the default linker, which can link anything no matter what.
factory.setPrioritizedLinkers(typeLinker, new DefaultLinker());
linker = factory.createLinker();
}
/**
* This is the method called by every call site in the bytecode to map it to a method handle.
*/
@SuppressWarnings("unused")
public static CallSite bootstrap(MethodHandles.Lookup lookup, String name, MethodType mType)
throws NoSuchMethodException {
Operation op = parseOperation(name);
// ChainedCallSite lets a call site have a few options for complex situations.
// It caches up to eight invocations, so that we can quickly select the best
// implementation in situations where the same call site is invoked in different
// contexts.
return linker.link(new ChainedCallSite(new CallSiteDescriptor(lookup, op, mType)));
}
/**
* Operation names in the bytecode are names like "PROP:GET:[NAME]" and "NAME:BIND:[NAME]". (See
* the "Signatures" interface for a description of these.) This method translates them the first
* time a call site is seen to an object that can be easily consumed by the various types of
* linkers.
*/
private static Operation parseOperation(String name) throws NoSuchMethodException {
String[] tokens = SEPARATOR.split(name, -1);
String namespaceName = getNameSegment(tokens, name, 0);
String opName = getNameSegment(tokens, name, 1);
if ("PROP".equals(namespaceName)) {
switch (opName) {
case "GET":
// Get an object property with a constant name
return StandardOperation.GET
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "GETNOWARN":
// Same with no warning of strict mode
return RhinoOperation.GETNOWARN
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "GETSUPER":
// Get an object property from super with a constant name
return RhinoOperation.GETSUPER
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "GETWITHTHIS":
// Same but also return "this" so that it is found by "lastStoredScriptable"
return RhinoOperation.GETWITHTHIS
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "GETWITHTHISOPTIONAL":
// Similar to the above, but won't complain if prop is not found
return RhinoOperation.GETWITHTHISOPTIONAL
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "GETELEMENT":
// Get the value of an element from a property that is on the stack,\
// as if using "[]" notation. Could be a String, number, or Symbol
return RhinoOperation.GETELEMENT.withNamespace(StandardNamespace.PROPERTY);
case "GETELEMENTSUPER":
// Get the value of an element from a property that is on the stack,\
// as if using "[]" notation. Could be a String, number, or Symbol
return RhinoOperation.GETELEMENTSUPER.withNamespace(StandardNamespace.PROPERTY);
case "GETINDEX":
// Same but the value is definitely a numeric index
return RhinoOperation.GETINDEX.withNamespace(StandardNamespace.PROPERTY);
case "SET":
// Set an object property with a constant name
return StandardOperation.SET
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "SETSUPER":
// Set an object property in super with a constant name
return RhinoOperation.SETSUPER
.withNamespace(StandardNamespace.PROPERTY)
.named(getNameSegment(tokens, name, 2));
case "SETELEMENT":
// Set an object property as if by "[]", with a property on the stack
return RhinoOperation.SETELEMENT.withNamespace(StandardNamespace.PROPERTY);
case "SETELEMENTSUPER":
// Set an object property in super as if by "[]", with a property on the stack
return RhinoOperation.SETELEMENTSUPER.withNamespace(StandardNamespace.PROPERTY);
case "SETINDEX":
// Same but the property name is definitely a number
return RhinoOperation.SETINDEX.withNamespace(StandardNamespace.PROPERTY);
}
} else if ("NAME".equals(namespaceName)) {
switch (opName) {
case "BIND":
// Bind a new variable to the context with a constant name
return RhinoOperation.BIND
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "GET":
// Get a variable from the context with a constant name
return StandardOperation.GET
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "GETWITHTHIS":
// Same but also return "this" so that it is found by "lastStoredScriptable"
return RhinoOperation.GETWITHTHIS
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "GETWITHTHISOPTIONAL":
// Similar to the above, but won't complain if prop is not found
return RhinoOperation.GETWITHTHISOPTIONAL
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "SET":
// Set an object in the context with a constant name
return StandardOperation.SET
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "SETSTRICT":
// Same but implement strict mode checks
return RhinoOperation.SETSTRICT
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
case "SETCONST":
// Same but try to set a constant
return RhinoOperation.SETCONST
.withNamespace(RhinoNamespace.NAME)
.named(getNameSegment(tokens, name, 2));
}
} else if ("MATH".equals(namespaceName)) {
switch (opName) {
case "ADD":
return RhinoOperation.ADD.withNamespace(RhinoNamespace.MATH);
case "TOBOOLEAN":
return RhinoOperation.TOBOOLEAN.withNamespace(RhinoNamespace.MATH);
case "TOINT32":
return RhinoOperation.TOINT32.withNamespace(RhinoNamespace.MATH);
case "TOUINT32":
return RhinoOperation.TOUINT32.withNamespace(RhinoNamespace.MATH);
case "EQ":
return RhinoOperation.EQ.withNamespace(RhinoNamespace.MATH);
case "SHALLOWEQ":
return RhinoOperation.SHALLOWEQ.withNamespace(RhinoNamespace.MATH);
case "TONUMBER":
return RhinoOperation.TONUMBER.withNamespace(RhinoNamespace.MATH);
case "TONUMERIC":
return RhinoOperation.TONUMERIC.withNamespace(RhinoNamespace.MATH);
case "COMPAREGT":
return RhinoOperation.COMPARE_GT.withNamespace(RhinoNamespace.MATH);
case "COMPARELT":
return RhinoOperation.COMPARE_LT.withNamespace(RhinoNamespace.MATH);
case "COMPAREGE":
return RhinoOperation.COMPARE_GE.withNamespace(RhinoNamespace.MATH);
case "COMPARELE":
return RhinoOperation.COMPARE_LE.withNamespace(RhinoNamespace.MATH);
}
}
// Fall through to no match. This will only happen if the name in the bytecode
// does not match the pattern that this method understands, which means that
// there is a mismatch between the bytecode and the runtime.
throw new NoSuchMethodException(name);
}
// Given a list of name segments and a position, return the interned name at the
// specified position. This allows us, to pull a name like "foo" from an operation
// named, for example, "NAME:GET:foo".
private static String getNameSegment(String[] segments, String name, int pos) {
if (pos >= segments.length) {
return "";
}
// The "slot maps" in ScriptableObject-based classes can shortcut when property names
// are "==", so interning strings improves performance in a measurable way, because
// the property names that we pull from the INDY operation descriptors are essentially
// constants.
return segments[pos].intern();
}
}