Trying to use the Bytecodes API to manipulatevalue arrays, it seems that the stack map generated by the CodeBuilder is incorrect. The generated class file is rejected by the verifier, and after disassembling the class file, the verifier seems to be right.

Here’s the code to generate the method:

static void testExecutionStackToValueArray(Class<?> valueClass, Class<?> containerClass) throws Throwable {
       final int ITERATIONS = 100;
       String sig = "()Q" + valueClass.getName() + ";";
       final String signature = sig.replace('.', '/');
       final String arraySignature = "[Q" + valueClass.getName().replace('.', '/') + ";";
       System.out.println(arraySignature);
       MethodHandle fromExecStackToValueArray = MethodHandleBuilder.loadCode(
               LOOKUP,
               "execStackToValueArray",
               MethodType.methodType(boolean.class),
               CODE -> {
                   CODE
                           .invokestatic(System.class, "gc", "()V", false)
                           .new_(containerClass)
                           .dup()
                           .invoke(MacroCodeBuilder.InvocationKind.INVOKESPECIAL, containerClass, "<init>", "()V", false)
                           .astore_1()
                           .ldc(ITERATIONS * 3)
                           .anewarray(valueClass)
                           .astore_2()
                           .iconst_m1()
                           .istore_3()
                           .label("loop")
                           .iload_3()
                           .ldc(ITERATIONS)
                           .ifcmp(TypeTag.I, CondKind.EQ, "end")
                           .iinc(3, 1)
                           .goto_("loop")
                           .label("end")
                           .iconst_1()
                           .return_(TypeTag.Z)
                           .label("failed")
                           .iconst_0()
                           .return_(TypeTag.Z);
               });
       boolean result = (boolean) fromExecStackToValueArray.invokeExact();
       System.out.println(result);
       assertTrue(result, "Invariant");
   }


And here’s the output of javap for the generated class file:


public class execStackToValueArray
 minor version: 0
 major version: 52
 flags: (0x0001) ACC_PUBLIC
 this_class: #24 // execStackToValueArray
 super_class: #2 // java/lang/Object
 interfaces: 0, fields: 0, methods: 1, attributes: 0
Constant pool:
  #1 = Utf8 java/lang/Object
  #2 = Class #1 // java/lang/Object
  #3 = Utf8 java/lang/System
  #4 = Class #3 // java/lang/System
  #5 = Utf8 gc
  #6 = Utf8 ()V
  #7 = NameAndType #5:#6 // gc:()V
  #8 = Methodref #4.#7 // java/lang/System.gc:()V
  #9 = Utf8 runtime/valhalla/valuetypes/ContainerValue1
 #10 = Class #9 // runtime/valhalla/valuetypes/ContainerValue1
 #11 = Utf8 <init>
 #12 = NameAndType #11:#6 // "<init>":()V
 #13 = Methodref #10.#12 // runtime/valhalla/valuetypes/ContainerValue1."<init>":()V
 #14 = Integer 300
 #15 = Utf8 ;Qruntime/valhalla/valuetypes/TestValue1;
 #16 = Class #15 // ";Qruntime/valhalla/valuetypes/TestValue1;"
 #17 = Utf8 [[Qruntime/valhalla/valuetypes/TestValue1;
 #18 = Class #17 // "[[Qruntime/valhalla/valuetypes/TestValue1;"
 #19 = Integer 100
 #20 = Utf8 Code
 #21 = Utf8 StackMapTable
 #22 = Utf8 execStackToValueArray
 #23 = Utf8 ()Z
 #24 = Class #22 // execStackToValueArray
{
 public static boolean execStackToValueArray();
   descriptor: ()Z
   flags: (0x0009) ACC_PUBLIC, ACC_STATIC
   Code:
     stack=2, locals=4, args_size=0
        0: invokestatic #8 // Method java/lang/System.gc:()V
        3: new #10 // class runtime/valhalla/valuetypes/ContainerValue1
        6: dup
        7: invokespecial #13 // Method runtime/valhalla/valuetypes/ContainerValue1."<init>":()V
       10: astore_1
       11: ldc #14 // int 300
       13: anewarray #16 // class ";Qruntime/valhalla/valuetypes/TestValue1;"
       16: astore_2
       17: iconst_m1
       18: istore_3
       19: iload_3
       20: ldc #19 // int 100
       22: if_icmpeq 31
       25: iinc 3, 1
       28: goto 19
       31: iconst_1
       32: ireturn
       33: iconst_0
       34: ireturn
     StackMapTable: number_of_entries = 3
       frame_type = 255 /* full_frame */
         offset_delta = 19
         locals = [ top, class runtime/valhalla/valuetypes/ContainerValue1, class "[[Qruntime/valhalla/valuetypes/TestValue1;", int ]
         stack = []
       frame_type = 11 /* same */
       frame_type = 1 /* same */
}


In the stack map, there’s an entry with a 2 dimensions value array, but the method creates only a single dimension value array.

The verifier detects the mismatch:

java.lang.IllegalStateException: java.lang.VerifyError: Instruction type does not match stack map
Exception Details:
 Location:
   runtime/valhalla/valuetypes/execStackToValueArray.execStackToValueArray()Z @19: iload_3
 Reason:
   Type '[Qruntime/valhalla/valuetypes/TestValue1;' (current frame, locals[2]) is not assignable to '[[Qruntime/valhalla/valuetypes/TestValue1;' (stack map, locals[2])
 Current Frame:
   bci: @19
   flags: { }
   locals: { top, 'runtime/valhalla/valuetypes/ContainerValue1', '[Qruntime/valhalla/valuetypes/TestValue1;', integer }
   stack: { }
 Stackmap Frame:
   bci: @19
   flags: { }
   locals: { top, 'runtime/valhalla/valuetypes/ContainerValue1', '[[Qruntime/valhalla/valuetypes/TestValue1;', integer }
   stack: { }
 Bytecode:
   0000000: b800 08bb 000a 59b7 000d 4c12 0ebd 0010
   0000010: 4d02 3e1d 1213 9f00 0984 0301 a7ff f704
   0000020: ac03 ac
 Stackmap Table:
   full_frame(@19,{Top,Object[#10],Object[#18],Integer},{})
   same_frame(@31)
   same_frame(@33)

at java.base/jdk.experimental.value.MethodHandleBuilder.loadCode(MethodHandleBuilder.java:105)
at java.base/jdk.experimental.value.MethodHandleBuilder.loadCode(MethodHandleBuilder.java:72)
at java.base/jdk.experimental.value.MethodHandleBuilder.loadCode(MethodHandleBuilder.java:67)
at runtime.valhalla.valuetypes.ValueTypesTest.testExecutionStackToValueArray(ValueTypesTest.java:307)
at runtime.valhalla.valuetypes.ValueTypesTest.main(ValueTypesTest.java:84)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.VerifyError: Instruction type does not match stack map