Java bytecode iconst_0 iadd sequence

Java bytecode iconst_0 iadd sequence

By : Sameer
Date : October 25 2020, 07:29 PM
it helps some times One thing to keep in mind is that javac (the Java Source code to byte code compiler) is not an optimizing compiler. In fact it is relatively simple in its code generation and only produces the most straight-forward byte-code implementation of any given source code.
That is entirely by design. This way the JVM, which is in charge of all the real optimizations, has the maximum amount of information available on which to base its decisions. In this particular case it might not be obvious how that information can benefit the JIT compiler, but due to the nature of optimizations done by HotSpot for example, every bit of information can help.
code :

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Is it possible to transform LLVM bytecode into Java bytecode?

Is it possible to transform LLVM bytecode into Java bytecode?

By : user2712373
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further It does now appear possible to convert LLVM IR bytecode to Java bytecode, using the LLJVM interpreter.
There is an interesting Disqus comment (21/03/11) from Grzegorz of kraytracing.com which explains, along with code, how he has modified LLJVM's Java class output routine to emit non-monolithic Java classes which agree in number with the input C/C++ modules. He suggests that his technique seems to avoid the excessively long 'compound' Java Constructor method argument signatures usually generated by LLJVM, and he provides links to his modifications and examples.
is fantom generated bytecode as performant as java equivalent bytecode?

is fantom generated bytecode as performant as java equivalent bytecode?

By : user3003889
Date : March 29 2020, 07:55 AM
I hope this helps you . from the many jvm languages appearing nowdays, there's one that seems to be particularly appealing , I did some quicksort performance testing.
code :
Int[100.000] array quicksort
  Java ~ 11ms
  Java using long and ArrayList<Long> ~ 66ms
  Fantom ~ 97 ms

Int[1.000.000] array quicksort
  Java ~ 91ms
  Java using long and ArrayList<long> ~ 815ms
  Fantom ~ 1100ms.
class TestQuickSort

   public static Void swap(Int[] a, Int i, Int j) {  
    temp := a[i];  
    a[i] = a[j];  
    a[j] = temp;  

   public static Void quicksortA(Int[] a, Int L, Int R) {  
    m := a[(L + R) / 2];  
    i := L;  
    j := R;  
    while (i <= j) {  
     while (a[i] < m)  
     while (a[j] > m)  
     if (i <= j) {  
      swap(a, i, j);  
    if (L < j)  
     quicksortA(a, L, j);  
    if (R > i)  
     quicksortA(a, i, R);  

   public static Void quicksort(Int[] a) {  
    quicksortA(a, 0, a.size - 1);  

  static Void main(Str[] args) {  

    // Sample data  
    a := Int[,]

    for(i := 0; i<1000000; i++)
      if(i%3==0) {a[i]=-a[i]}

    t1 := Duration.now 
    t2 := Duration.now 

import java.util.ArrayList;
public class QuicksortJava {  

 public static void swap(ArrayList<Long> a, long i, long j) {  
  long temp = a.get((int)i);  
  a.set((int)i, a.get((int)j));  
  a.set((int)j, temp);  

 public static void quicksort(ArrayList<Long> a, long L, long R) {  
  long m = a.get((int)(L + R) / 2);  
  long i =  L;  
  long j =  R;  
  while (i <= j) {  
   while (a.get((int)i) < m)  
   while (a.get((int)j) > m)  
   if (i <= j) {  
    swap(a, i, j);  
  if (L < j)  
   quicksort(a, L, j);  
  if (R > i)  
   quicksort(a, i, R);  

 public static void quicksort(ArrayList<Long> a) {  
  quicksort(a, 0, a.size() - 1);  

 public static void main(String[] args) {  

  // Sample data  
  long size = 100000;
  ArrayList<Long> a = new ArrayList<Long>((int)size);  
  for (long i = 0; i < size; i++) {  
   a.add(i * 3 / 2 + 1);  
   if (i % 3 == 0)  
    a.set((int)i, -a.get((int)i));  

  long t1 = System.currentTimeMillis();  
  long t2 = System.currentTimeMillis();  
  System.out.println(t2 - t1);  


combine multiple java method bytecode sequence

combine multiple java method bytecode sequence

By : kptan
Date : March 29 2020, 07:55 AM
it fixes the issue Yes, it is possible, with a few minor restrictions. The main restriction is that a single method's bytecode is limited to 65535 bytes, but you're unlikely to run into this restriction in practice. The number of exception handlers, local variable slots, and operand stack size in a single method are also limited, though these are even less likely to be reached.
How to force Delphi to use D8.bat instead of dx.bat to compile Java 1.8 bytecode into DEX bytecode

How to force Delphi to use D8.bat instead of dx.bat to compile Java 1.8 bytecode into DEX bytecode

By : xc0
Date : March 29 2020, 07:55 AM
With these it helps I found a solution modifying the "CodeGear.Common.Targets" file (Delphi's bin folder), creating an alternative command to be used only for dex generation using the d8.bat instead of the dx.bat:
1) Close the IDE
code :
<D8Cmd>PATH $(JDKPath)\bin;$(PATH) %26 "$(JavaD8Path)" --output=</D8Cmd>
  <!-- Generate a "dexed" version of the customized jar files if they doesn´t exists -->
  <Target Name="BuildPredexedJar" DependsOnTargets="GetProjectJars">
    <Exec Condition="( '@(_JarsLocations)'!='' And !Exists('%(_JarsLocations.PredexedJar)') )"
        Command='$(D8Cmd)"%(_JarsLocations.PredexedJar)" %22%(_JarsLocations.FullPath)%22'/>
How to add an extra instruction to method in ByteCode using ClassVisitor / Java Bytecode (ASM)

How to add an extra instruction to method in ByteCode using ClassVisitor / Java Bytecode (ASM)

By : Anthony Reed
Date : March 29 2020, 07:55 AM
I hope this helps . There is example code to insert your line at the beggining of the function
code :
public class YourClassVisitor extends ClassVisitor {
    public YourClassVisitor(ClassVisitor cv) {
        super(Opcodes.ASM5, cv);

    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        if (name.equals("targetName")) {
            return new YourMethodVisitor(super.visitMethod(access, name, desc, signature, exceptions));
        return super.visitMethod(access, name, desc, signature, exceptions);

    private static class YourMethodVisitor extends MethodVisitor {
        public YourMethodVisitor(MethodVisitor mv) {
            super(Opcodes.ASM5, mv);

        // This method will be called before almost all instructions
        public void visitCode() {
            // Default implementation is empty. So we haven't to call super method

            // Puts 'this' on top of the stack. If your method is static just delete it
            visitVarInsn(Opcodes.ALOAD, 0);
            // Takes instance of class "the/full/name/of/your/Class" from top of the stack and put value of field interceptors
            // "Ljava/util/List;" is just internal name of java.util.List
            // If your field is static just replace GETFIELD with GETSTATIC
            visitFieldInsn(Opcodes.GETFIELD, "the/full/name/of/your/Class", "interceptors", "Ljava/util/List;");
            // Before we call add method of list we have to put target value on top of the stack
            // New object creation starts with creating not initialized instance of it
            visitTypeInsn(Opcodes.NEW, "com/shehabic/sherlock/interceptors");
            // Than we just copy it
            visitTypeInsn(Opcodes.NEW, "example/path/to/class/SherlockOkHttpInterceptor");
            // We have to call classes constructor
            // Internal name of constructor - <init>
            // ()V - signature of method. () - method doesn't have parameters. V - method returns void
            visitMethodInsn(Opcodes.INVOKESPECIAL, "example/path/to/class/SherlockOkHttpInterceptor", "<init>", "()V", false);
            // So on top of the stack we have initialized instance of example/path/to/class/SherlockOkHttpInterceptor
            // Now we can call constructor of com/shehabic/sherlock/interceptors
            visitMethodInsn(Opcodes.INVOKESPECIAL, "com/shehabic/sherlock/interceptors", "<init>", "(Lexample/path/to/class/SherlockOkHttpInterceptor;)V", false);
            // So on top of the stack we have initialized instance of com/shehabic/sherlock/interceptors
            // Now we can put it into list
            visitMethodInsn(Opcodes.INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true);


        byte[] cache = null;
        try (FileInputStream in = new FileInputStream("C:\\Users\\JustAGod\\Projects\\gloomymods\\BuildTools\\BytecodeTools\\out\\production\\classes\\gloomyfolken\\Kek.class")) {
            ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
            ClassReader reader = new ClassReader(in);
            reader.accept(new YourClassVisitor(writer), ClassReader.EXPAND_FRAMES);
            cache = writer.toByteArray();
        } catch (IOException e) {
        try(FileOutputStream out = new FileOutputStream("C:\\Users\\JustAGod\\Projects\\gloomymods\\BuildTools\\BytecodeTools\\out\\production\\classes\\gloomyfolken\\Kek.class")) {
        } catch (IOException e) {
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