1 /*
  2  * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  8  * particular file as subject to the "Classpath" exception as provided
  9  * by Oracle in the LICENSE file that accompanied this code.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package jdk.incubator.code.interpreter;
 27 
 28 import java.lang.invoke.*;
 29 import java.lang.reflect.Array;
 30 import java.lang.reflect.InvocationHandler;
 31 import java.lang.reflect.Method;
 32 import java.lang.reflect.Proxy;
 33 import jdk.incubator.code.*;
 34 import jdk.incubator.code.dialect.core.CoreOp;
 35 import jdk.incubator.code.dialect.core.FunctionType;
 36 import jdk.incubator.code.dialect.core.VarType;
 37 import jdk.incubator.code.dialect.java.*;
 38 import jdk.incubator.code.TypeElement;
 39 import jdk.incubator.code.internal.ArithmeticAndConvOpImpls;
 40 
 41 import java.util.*;
 42 import java.util.concurrent.locks.ReentrantLock;
 43 import java.util.stream.Collectors;
 44 import java.util.stream.Stream;
 45 
 46 import static java.util.stream.Collectors.toMap;
 47 
 48 /**
 49  * A code model interpreter that sequentially executes operations contained in an
 50  * {@link Op.Invokable} operation, such as a function operation.
 51  */
 52 public final class Interpreter {
 53     private Interpreter() {
 54     }
 55 
 56     /**
 57      * Invokes an invokable operation by interpreting the code elements within
 58      * the operations body.
 59      * <p>
 60      * The sequence of arguments must consists of objects corresponding, in order,
 61      * to the invokable operation's {@link Op.Invokable#parameters() parameters}.
 62      * If the invokable operation {@link Op.Invokable#capturedValues() captures values}
 63      * then the sequence of arguments must be appended with objects corresponding,
 64      * in order, to the captured values.
 65      *
 66      * @param l the lookup to use for interpreting reflective operations.
 67      * @param op the invokeable operation to interpret.
 68      * @param args the invokeable's arguments appended with captured arguments, if any.
 69      * @return the interpreter result of invokable operation.
 70      * @param <T> the type of Invokable.
 71      * @throws InterpreterException if there is a failure to interpret
 72      */
 73     public static <T extends Op & Op.Invokable>
 74     Object invoke(MethodHandles.Lookup l, T op,
 75                   Object... args) {
 76         // Arguments can contain null values so we cannot use List.of
 77         return invoke(l, op, Arrays.asList(args));
 78     }
 79 
 80     /**
 81      * Invokes an invokable operation by interpreting the code elements within
 82      * the operations body.
 83      * <p>
 84      * The list of arguments must consists of objects corresponding, in order,
 85      * to the invokable operation's {@link Op.Invokable#parameters() parameters}.
 86      * If the invokable operation {@link Op.Invokable#capturedValues() captures values}
 87      * then the list of arguments must be appended with objects corresponding,
 88      * in order, to the captured values.
 89      *
 90      * @param l the lookup to use for interpreting reflective operations.
 91      * @param op the invokeable operation to interpret.
 92      * @param args the invokeable's arguments appended with captured arguments, if any.
 93      * @return the interpreter result of invokable operation.
 94      * @param <T> the type of Invokable.
 95      * @throws InterpreterException if there is a failure to interpret
 96      */
 97     public static <T extends Op & Op.Invokable>
 98     Object invoke(MethodHandles.Lookup l, T op,
 99                   List<Object> args) {
100         List<Block.Parameter> parameters = op.parameters();
101         List<Value> capturedValues = op.capturedValues();
102         if (parameters.size() + capturedValues.size() != args.size()) {
103             throw interpreterException(new IllegalArgumentException(
104                     String.format("Actual #arguments (%d) differs from #parameters (%d) plus #captured arguments (%d)",
105                             args.size(), parameters.size(), capturedValues.size())));
106         }
107         // validate runtime args types
108         List<Value> symbolicValues = Stream.concat(parameters.stream(), capturedValues.stream()).toList();
109         for (int i = 0; i < symbolicValues.size(); i++) {
110             Value sv = symbolicValues.get(i);
111             Object rv = args.get(i);
112             try {
113                 JavaType typeToResolve = switch (sv.type()) {
114                     // @@@ Deconstruct and test what the var holds
115                     case VarType _ -> JavaType.type(CoreOp.Var.class);
116                     // Allow reflection to convert between primitive values
117                     // @@@ Check conversion compatible
118                     case PrimitiveType _ -> JavaType.J_L_OBJECT;
119                     case JavaType jt -> jt;
120                     default -> throw new IllegalStateException("Unexpected type: " + sv.type());
121                 };
122                 Class<?> c = typeToResolve.toNominalDescriptor().resolveConstantDesc(l);
123                 if (rv != null && !c.isInstance(rv)) {
124                     throw interpreterException(new IllegalArgumentException(("Runtime argument at position %d has type %s " +
125                             "but the corresponding symbolic value has type %s").formatted(i, rv.getClass(), sv.type())));
126                 }
127             } catch (ReflectiveOperationException e) {
128                 throw new RuntimeException(e);
129             }
130         }
131         // Map symbolic parameters to runtime arguments
132         Map<Value, Object> valuesAndArguments = new HashMap<>();
133         for (int i = 0; i < parameters.size(); i++) {
134             valuesAndArguments.put(parameters.get(i), args.get(i));
135         }
136         // Map symbolic captured values to the additional runtime arguments
137         for (int i = 0; i < capturedValues.size(); i++) {
138             valuesAndArguments.put(capturedValues.get(i), args.get(parameters.size() + i));
139         }
140 
141         return interpretEntryBlock(l, op.body().entryBlock(), new OpContext(), valuesAndArguments);
142     }
143 
144 
145     /**
146      * Exception thrown by the interpreter when execution fails.
147      */
148     @SuppressWarnings("serial")
149     public static final class InterpreterException extends RuntimeException {
150         private InterpreterException(Throwable cause) {
151             super(cause);
152         }
153     }
154 
155     static InterpreterException interpreterException(Throwable cause) {
156         return new InterpreterException(cause);
157     }
158 
159     record BlockContext(Block b, Map<Value, Object> valuesAndArguments) {
160     }
161 
162     static final class OpContext {
163         final Map<Object, ReentrantLock> locks = new HashMap<>();
164         final Deque<BlockContext> stack = new ArrayDeque<>();
165         final Deque<ExceptionRegionRecord> erStack = new ArrayDeque<>();
166 
167         Object getValue(Value v) {
168             // @@@ Only dominating values are accessible
169             BlockContext bc = findContext(v);
170             if (bc != null) {
171                 return bc.valuesAndArguments.get(v);
172             } else {
173                 throw interpreterException(new IllegalArgumentException("Undefined value: " + v));
174             }
175         }
176 
177         Object setValue(Value v, Object o) {
178             BlockContext bc = findContext(v);
179             if (bc != null) {
180                 throw interpreterException(new IllegalArgumentException("Value already defined: " + v));
181             }
182             stack.peek().valuesAndArguments.put(v, o);
183             return o;
184         }
185 
186         BlockContext findContext(Value v) {
187             Optional<BlockContext> ob = stack.stream().filter(b -> b.valuesAndArguments.containsKey(v)).findFirst();
188             return ob.orElse(null);
189         }
190 
191         boolean contains(Block.Reference s) {
192             Block sb = s.targetBlock();
193             return stack.stream().anyMatch(bc -> bc.b.equals(sb));
194         }
195 
196         void successor(Block.Reference sb) {
197             List<Object> sbValues = sb.arguments().stream().map(this::getValue).toList();
198 
199             Block b = sb.targetBlock();
200             Map<Value, Object> bValues = new HashMap<>();
201             for (int i = 0; i < sbValues.size(); i++) {
202                 bValues.put(b.parameters().get(i), sbValues.get(i));
203             }
204 
205             if (contains(sb)) {
206                 // if block is already dominating pop back up from the back branch to the block
207                 // before the successor block
208                 while (!stack.peek().b.equals(sb.targetBlock())) {
209                     stack.pop();
210                 }
211                 stack.pop();
212             }
213             stack.push(new BlockContext(b, bValues));
214         }
215 
216         void successor(Block b, Map<Value, Object> bValues) {
217             stack.push(new BlockContext(b, bValues));
218         }
219 
220         void popTo(BlockContext bc) {
221             while (!stack.peek().equals(bc)) {
222                 stack.pop();
223             }
224         }
225 
226         void pushExceptionRegion(ExceptionRegionRecord erb) {
227             erStack.push(erb);
228         }
229 
230         void popExceptionRegion(JavaOp.ExceptionRegionExit ere) {
231             ere.catchBlocks().forEach(catchBlock -> {
232                 if (erStack.peek().catchBlock != catchBlock.targetBlock()) {
233                     // @@@ Use internal exception type
234                     throw interpreterException(new IllegalStateException("Mismatched exception regions"));
235                 }
236                 erStack.pop();
237             });
238         }
239 
240         Block exception(MethodHandles.Lookup l, Throwable e) {
241             // Find the first matching exception region
242             // with a catch block whose argument type is assignable-compatible to the throwable
243             ExceptionRegionRecord er;
244             Block cb = null;
245             while ((er = erStack.poll()) != null &&
246                     (cb = er.match(l, e)) == null) {
247             }
248 
249             if (er == null) {
250                 return null;
251             }
252 
253             // Pop the block context to the block defining the start of the exception region
254             popTo(er.mark);
255             while (erStack.size() > er.erStackDepth()) {
256                 erStack.pop();
257             }
258             return cb;
259         }
260     }
261 
262     static final class VarBox
263             implements CoreOp.Var<Object> {
264         Object value;
265 
266         public Object value() {
267             return value;
268         }
269 
270         VarBox(Object value) {
271             this.value = value;
272         }
273 
274         static final Object UINITIALIZED = new Object();
275     }
276 
277     record TupleRecord(List<Object> components) {
278         Object getComponent(int index) {
279             return components.get(index);
280         }
281 
282         TupleRecord with(int index, Object value) {
283             List<Object> copy = new ArrayList<>(components);
284             copy.set(index, value);
285             return new TupleRecord(copy);
286         }
287     }
288 
289     record ExceptionRegionRecord(BlockContext mark, int erStackDepth, Block catchBlock) {
290         Block match(MethodHandles.Lookup l, Throwable e) {
291             List<Block.Parameter> args = catchBlock.parameters();
292             if (args.size() != 1) {
293                 throw interpreterException(new IllegalStateException("Catch block must have one argument"));
294             }
295             TypeElement et = args.get(0).type();
296             if (et instanceof VarType vt) {
297                 et = vt.valueType();
298             }
299             if (resolveToClass(l, et).isInstance(e)) {
300                 return catchBlock;
301             }
302             return null;
303         }
304     }
305 
306     static Object interpretBody(MethodHandles.Lookup l, Body body,
307                                 OpContext oc,
308                                 List<Object> args) {
309         List<Block.Parameter> parameters = body.entryBlock().parameters();
310         if (parameters.size() != args.size()) {
311             throw interpreterException(new IllegalArgumentException(
312                     "Incorrect number of arguments arguments"));
313         }
314 
315         // Map symbolic parameters to runtime arguments
316         Map<Value, Object> arguments = new HashMap<>();
317         for (int i = 0; i < parameters.size(); i++) {
318             arguments.put(parameters.get(i), args.get(i));
319         }
320 
321         return interpretEntryBlock(l, body.entryBlock(), oc, arguments);
322     }
323 
324     static Object interpretEntryBlock(MethodHandles.Lookup l, Block entry,
325                                       OpContext oc,
326                                       Map<Value, Object> valuesAndArguments) {
327         assert entry.isEntryBlock();
328 
329         // If the stack is not empty it means we are interpreting
330         // an entry block with a parent body whose nearest ancestor body
331         // is the current context block's parent body
332         BlockContext yieldContext = oc.stack.peek();
333         assert yieldContext == null ||
334                 yieldContext.b().ancestorBody() == entry.ancestorBody().ancestorBody();
335 
336         // Note that first block cannot have any successors so the queue will have at least one entry
337         oc.stack.push(new BlockContext(entry, valuesAndArguments));
338         while (true) {
339             BlockContext bc = oc.stack.peek();
340 
341             // Execute all but the terminating operation
342             int nops = bc.b.ops().size();
343             try {
344                 for (int i = 0; i < nops - 1; i++) {
345                     Op op = bc.b.ops().get(i);
346                     assert !(op instanceof Op.Terminating) : op;
347 
348                     Object result = interpretOp(l, oc, op);
349                     oc.setValue(op.result(), result);
350                 }
351             } catch (InterpreterException e) {
352                 throw e;
353             } catch (Throwable t) {
354                 processThrowable(oc, l, t);
355                 continue;
356             }
357 
358             // Execute the terminating operation
359             Op to = bc.b.terminatingOp();
360             if (to instanceof CoreOp.ConditionalBranchOp cb) {
361                 boolean p;
362                 Object bop = oc.getValue(cb.predicate());
363                 if (bop instanceof Boolean bp) {
364                     p = bp;
365                 } else if (bop instanceof Integer ip) {
366                     // @@@ This is required when lifting up from bytecode, since boolean values
367                     // are erased to int values, abd the bytecode lifting implementation is not currently
368                     // sophisticated enough to recover the type information
369                     p = ip != 0;
370                 } else {
371                     throw interpreterException(
372                             new UnsupportedOperationException("Unsupported type input to operation: " + cb));
373                 }
374                 Block.Reference sb = p ? cb.trueBranch() : cb.falseBranch();
375                 oc.successor(sb);
376             } else if (to instanceof CoreOp.BranchOp b) {
377                 Block.Reference sb = b.branch();
378 
379                 oc.successor(sb);
380             } else if (to instanceof JavaOp.ThrowOp _throw) {
381                 Throwable t = (Throwable) oc.getValue(_throw.argument());
382                 processThrowable(oc, l, t);
383             } else if (to instanceof CoreOp.ReturnOp ret) {
384                 Value rv = ret.returnValue();
385                 return rv == null ? null : oc.getValue(rv);
386             } else if (to instanceof CoreOp.YieldOp yop) {
387                 if (yieldContext == null) {
388                     throw interpreterException(
389                             new IllegalStateException("Yielding to no parent body"));
390                 }
391                 Value yv = yop.yieldValue();
392                 Object yr = yv == null ? null : oc.getValue(yv);
393                 oc.popTo(yieldContext);
394                 return yr;
395             } else if (to instanceof JavaOp.ExceptionRegionEnter ers) {
396                 int erStackDepth = oc.erStack.size();
397                 ers.catchBlocks().forEach(catchBlock -> {
398                     var er = new ExceptionRegionRecord(oc.stack.peek(), erStackDepth, catchBlock.targetBlock());
399                     oc.pushExceptionRegion(er);
400                 });
401 
402                 oc.successor(ers.start());
403             } else if (to instanceof JavaOp.ExceptionRegionExit ere) {
404                 oc.popExceptionRegion(ere);
405 
406                 oc.successor(ere.end());
407             } else {
408                 throw interpreterException(
409                         new UnsupportedOperationException("Unsupported terminating operation: " + to));
410             }
411         }
412     }
413 
414     static void processThrowable(OpContext oc, MethodHandles.Lookup l, Throwable t) {
415         // Find a matching catch block
416         Block cb = oc.exception(l, t);
417         if (cb == null) {
418             // If there is no matching catch bock then rethrow back to the caller
419             eraseAndThrow(t);
420             throw new InternalError("should not reach here");
421         }
422 
423         // Add a new block context to the catch block with the exception as the argument
424         Map<Value, Object> bValues = new HashMap<>();
425         Block.Parameter eArg = cb.parameters().get(0);
426         if (eArg.type() instanceof VarType) {
427             bValues.put(eArg, new VarBox(t));
428         } else {
429             bValues.put(eArg, t);
430         }
431         oc.successor(cb, bValues);
432     }
433 
434     @SuppressWarnings("unchecked")
435     static <E extends Throwable> void eraseAndThrow(Throwable e) throws E {
436         throw (E) e;
437     }
438 
439     static Object interpretOp(MethodHandles.Lookup l, OpContext oc, Op o) {
440         if (o instanceof CoreOp.ConstantOp co) {
441             if (co.resultType().equals(JavaType.J_L_CLASS)) {
442                 return resolveToClass(l, (JavaType) co.value());
443             } else {
444                 return co.value();
445             }
446         } else if (o instanceof CoreOp.FuncCallOp fco) {
447             String name = fco.funcName();
448 
449             // Find top-level op
450             Op top = fco;
451             while (top.ancestorBody() != null) {
452                 top = top.ancestorOp();
453             }
454 
455             // Ensure top-level op is a module and function name
456             // is in the module's function table
457             if (top instanceof CoreOp.ModuleOp mop) {
458                 CoreOp.FuncOp funcOp = mop.functionTable().get(name);
459                 if (funcOp == null) {
460                     throw interpreterException(
461                             new IllegalStateException
462                                     ("Function " + name + " cannot be resolved: not in module's function table"));
463                 }
464 
465                 List<Object> values = o.operands().stream().map(oc::getValue).toList();
466                 return Interpreter.invoke(l, funcOp, values);
467             } else {
468                 throw interpreterException(
469                         new IllegalStateException(
470                                 "Function " + name + " cannot be resolved: top level op is not a module"));
471             }
472         } else if (o instanceof JavaOp.InvokeOp co) {
473             MethodType target = resolveToMethodType(l, o.opType());
474             MethodHandles.Lookup il = switch (co.invokeKind()) {
475                 case STATIC, INSTANCE -> l;
476                 case SUPER -> l.in(target.parameterType(0));
477             };
478         MethodHandle mh = resolveToMethodHandle(il, co.invokeReference(), co.invokeKind());
479 
480             mh = mh.asType(target).asFixedArity();
481             Object[] values = o.operands().stream().map(oc::getValue).toArray();
482             return invoke(mh, values);
483         } else if (o instanceof JavaOp.NewOp no) {
484             Object[] values = o.operands().stream().map(oc::getValue).toArray();
485         MethodHandle mh = resolveToConstructorHandle(l, no.constructorReference());
486             return invoke(mh, values);
487         } else if (o instanceof CoreOp.QuotedOp qo) {
488             SequencedMap<Value, Object> capturedValues = qo.capturedValues().stream()
489                     .collect(toMap(v -> v, oc::getValue, (v, _) -> v, LinkedHashMap::new));
490             return new Quoted<>(qo.quotedOp(), capturedValues);
491         } else if (o instanceof JavaOp.LambdaOp lo) {
492             SequencedMap<Value, Object> capturedValuesAndArguments = lo.capturedValues().stream()
493                     .collect(toMap(v -> v, oc::getValue, (v, _) -> v, LinkedHashMap::new));
494             Class<?> fi = resolveToClass(l, lo.functionalInterface());
495 
496             Object[] capturedArguments = capturedValuesAndArguments.sequencedValues().toArray(Object[]::new);
497             MethodHandle fProxy = INVOKE_LAMBDA_MH.bindTo(l).bindTo(lo).bindTo(capturedArguments)
498                     .asCollector(Object[].class, lo.parameters().size());
499             Object fiInstance = MethodHandleProxies.asInterfaceInstance(fi, fProxy);
500 
501             // If a reflectable lambda proxy again to add method Quoted quoted()
502             if (lo.isReflectable()) {
503                 return Proxy.newProxyInstance(l.lookupClass().getClassLoader(), new Class<?>[]{fi},
504                         new InvocationHandler() {
505                             private final Quoted<JavaOp.LambdaOp> quoted = new Quoted<>(lo, capturedValuesAndArguments);
506                             @Override
507                             public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
508                                 if (Objects.equals(method.getName(), "quoted") && method.getParameterCount() == 0) {
509                                     return __internal_quoted();
510                                 } else {
511                                     // Delegate to FI instance
512                                     return method.invoke(fiInstance, args);
513                                 }
514                             }
515 
516                             private Quoted<JavaOp.LambdaOp> __internal_quoted() {
517                                 return quoted;
518                             }
519                         });
520             } else {
521                 return fiInstance;
522             }
523         } else if (o instanceof CoreOp.VarOp vo) {
524             Object v = vo.isUninitialized()
525                     ? VarBox.UINITIALIZED
526                     : oc.getValue(o.operands().get(0));
527             return new VarBox(v);
528         } else if (o instanceof CoreOp.VarAccessOp.VarLoadOp vlo) {
529             // Cast to CoreOp.Var, since the instance may have originated as an external instance
530             // via a captured value map
531             CoreOp.Var<?> vb = (CoreOp.Var<?>) oc.getValue(o.operands().get(0));
532             Object value = vb.value();
533             if (value == VarBox.UINITIALIZED) {
534                 throw interpreterException(new IllegalStateException("Loading from uninitialized variable"));
535             }
536             return value;
537         } else if (o instanceof CoreOp.VarAccessOp.VarStoreOp vso) {
538             VarBox vb = (VarBox) oc.getValue(o.operands().get(0));
539             vb.value = oc.getValue(o.operands().get(1));
540             return null;
541         } else if (o instanceof CoreOp.TupleOp to) {
542             List<Object> values = o.operands().stream().map(oc::getValue).toList();
543             return new TupleRecord(values);
544         } else if (o instanceof CoreOp.TupleLoadOp tlo) {
545             TupleRecord tb = (TupleRecord) oc.getValue(o.operands().get(0));
546             return tb.getComponent(tlo.index());
547         } else if (o instanceof CoreOp.TupleWithOp two) {
548             TupleRecord tb = (TupleRecord) oc.getValue(o.operands().get(0));
549             return tb.with(two.index(), oc.getValue(o.operands().get(1)));
550         } else if (o instanceof JavaOp.FieldAccessOp.FieldLoadOp fo) {
551             if (fo.operands().isEmpty()) {
552         VarHandle vh = fieldStaticHandle(l, fo.fieldReference());
553                 return vh.get();
554             } else {
555                 Object v = oc.getValue(o.operands().get(0));
556         VarHandle vh = fieldHandle(l, fo.fieldReference());
557                 return vh.get(v);
558             }
559         } else if (o instanceof JavaOp.FieldAccessOp.FieldStoreOp fo) {
560             if (fo.operands().size() == 1) {
561                 Object v = oc.getValue(o.operands().get(0));
562         VarHandle vh = fieldStaticHandle(l, fo.fieldReference());
563                 vh.set(v);
564             } else {
565                 Object r = oc.getValue(o.operands().get(0));
566                 Object v = oc.getValue(o.operands().get(1));
567         VarHandle vh = fieldHandle(l, fo.fieldReference());
568                 vh.set(r, v);
569             }
570             return null;
571         } else if (o instanceof JavaOp.InstanceOfOp io) {
572             Object v = oc.getValue(o.operands().get(0));
573             return isInstance(l, io.targetType(), v);
574         } else if (o instanceof JavaOp.CastOp co) {
575             Object v = oc.getValue(o.operands().get(0));
576             return cast(l, co.targetType(), v);
577         } else if (o instanceof JavaOp.ArrayLengthOp) {
578             Object a = oc.getValue(o.operands().get(0));
579             return Array.getLength(a);
580         } else if (o instanceof JavaOp.ArrayAccessOp.ArrayLoadOp) {
581             Object a = oc.getValue(o.operands().get(0));
582             Object index = oc.getValue(o.operands().get(1));
583             return Array.get(a, (int) index);
584         } else if (o instanceof JavaOp.ArrayAccessOp.ArrayStoreOp) {
585             Object a = oc.getValue(o.operands().get(0));
586             Object index = oc.getValue(o.operands().get(1));
587             Object v = oc.getValue(o.operands().get(2));
588             Array.set(a, (int) index, v);
589             return null;
590         } else if (o instanceof JavaOp.ArithmeticOperation) {
591             // @@@ avoid use of opName
592             MethodHandle mh = opHandle(l, o.externalizeOpName(), o.opType());
593             Object[] values = o.operands().stream().map(oc::getValue).toArray();
594             return invoke(mh, values);
595         } else if (o instanceof JavaOp.ConvOp) {
596             // @@@ avoid use of opName
597             MethodHandle mh = opHandle(l, o.externalizeOpName() + "_" + o.opType().returnType(), o.opType());
598             Object[] values = o.operands().stream().map(oc::getValue).toArray();
599             return invoke(mh, values);
600         } else if (o instanceof JavaOp.AssertOp _assert) {
601             Body testBody = _assert.bodies().get(0);
602             boolean testResult = (boolean) interpretBody(l, testBody, oc, List.of());
603             if (!testResult) {
604                 if (_assert.bodies().size() > 1) {
605                     Body messageBody = _assert.bodies().get(1);
606                     String message = String.valueOf(interpretBody(l, messageBody, oc, List.of()));
607                     throw new AssertionError(message);
608                 } else {
609                     throw new AssertionError();
610                 }
611             }
612             return null;
613         } else if (o instanceof JavaOp.ConcatOp) {
614             return o.operands().stream()
615                     .map(oc::getValue)
616                     .map(String::valueOf)
617                     .collect(Collectors.joining());
618         } else if (o instanceof JavaOp.MonitorOp.MonitorEnterOp) {
619             Object monitorTarget = oc.getValue(o.operands().get(0));
620             if (monitorTarget == null) {
621                 throw new NullPointerException();
622             }
623             ReentrantLock lock = oc.locks.computeIfAbsent(monitorTarget, _ -> new ReentrantLock());
624             lock.lock();
625             return null;
626         } else if (o instanceof JavaOp.MonitorOp.MonitorExitOp) {
627             Object monitorTarget = oc.getValue(o.operands().get(0));
628             if (monitorTarget == null) {
629                 throw new NullPointerException();
630             }
631             ReentrantLock lock = oc.locks.get(monitorTarget);
632             if (lock == null) {
633                 throw new IllegalMonitorStateException();
634             }
635             lock.unlock();
636             return null;
637         } else {
638             throw interpreterException(
639                     new UnsupportedOperationException("Unsupported operation: " + o));
640         }
641     }
642 
643     static final MethodHandle INVOKE_LAMBDA_MH;
644     static {
645         try {
646             INVOKE_LAMBDA_MH = MethodHandles.lookup().findStatic(Interpreter.class, "invokeLambda",
647                     MethodType.methodType(Object.class, MethodHandles.Lookup.class,
648                             JavaOp.LambdaOp.class, Object[].class, Object[].class));
649         } catch (Throwable t) {
650             throw new InternalError(t);
651         }
652     }
653 
654     static Object invokeLambda(MethodHandles.Lookup l, JavaOp.LambdaOp op, Object[] capturedArgs, Object[] args) {
655         List<Object> arguments = new ArrayList<>(Arrays.asList(args));
656         arguments.addAll(Arrays.asList(capturedArgs));
657         return invoke(l, op, arguments);
658     }
659 
660     static MethodHandle opHandle(MethodHandles.Lookup l, String opName, FunctionType ft) {
661         MethodType mt = resolveToMethodType(l, ft).erase();
662         try {
663             return MethodHandles.lookup().findStatic(ArithmeticAndConvOpImpls.class, opName, mt);
664         } catch (NoSuchMethodException | IllegalAccessException e) {
665             throw interpreterException(e);
666         }
667     }
668 
669     static VarHandle fieldStaticHandle(MethodHandles.Lookup l, FieldRef d) {
670         return resolveToVarHandle(l, d);
671     }
672 
673     static VarHandle fieldHandle(MethodHandles.Lookup l, FieldRef d) {
674         return resolveToVarHandle(l, d);
675     }
676 
677     static Object isInstance(MethodHandles.Lookup l, TypeElement d, Object v) {
678         Class<?> c = resolveToClass(l, d);
679         return c.isInstance(v);
680     }
681 
682     static Object cast(MethodHandles.Lookup l, TypeElement d, Object v) {
683         Class<?> c = resolveToClass(l, d);
684         return c.cast(v);
685     }
686 
687     static MethodHandle resolveToMethodHandle(MethodHandles.Lookup l, MethodRef d, JavaOp.InvokeOp.InvokeKind kind) {
688         try {
689             return d.resolveToHandle(l, kind);
690         } catch (ReflectiveOperationException e) {
691             throw interpreterException(e);
692         }
693     }
694 
695     static MethodHandle resolveToConstructorHandle(MethodHandles.Lookup l, MethodRef d) {
696         try {
697             return d.resolveToHandle(l, JavaOp.InvokeOp.InvokeKind.SUPER);
698         } catch (ReflectiveOperationException e) {
699             throw interpreterException(e);
700         }
701     }
702 
703     static VarHandle resolveToVarHandle(MethodHandles.Lookup l, FieldRef d) {
704         try {
705             return d.resolveToHandle(l);
706         } catch (ReflectiveOperationException e) {
707             throw interpreterException(e);
708         }
709     }
710 
711     static MethodType resolveToMethodType(MethodHandles.Lookup l, FunctionType ft) {
712         try {
713             return MethodRef.toNominalDescriptor(ft).resolveConstantDesc(l);
714         } catch (ReflectiveOperationException e) {
715             throw interpreterException(e);
716         }
717     }
718 
719     static Class<?> resolveToClass(MethodHandles.Lookup l, TypeElement d) {
720         try {
721             if (d instanceof JavaType jt) {
722                 return (Class<?>)jt.erasure().resolve(l);
723             } else {
724                 throw new ReflectiveOperationException();
725             }
726         } catch (ReflectiveOperationException e) {
727             throw interpreterException(e);
728         }
729     }
730 
731     static Object invoke(MethodHandle m, Object... args) {
732         try {
733             return m.invokeWithArguments(args);
734         } catch (RuntimeException | Error e) {
735             throw e;
736         } catch (Throwable e) {
737             eraseAndThrow(e);
738             throw new InternalError("should not reach here");
739         }
740     }
741 }