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 package org.jruby.ir.operands;
 
 
 import java.util.List;

Operands extending this type can make a reasonable assumption of immutability. In Ruby, almost nothing is truly immutable (set_instance_var) but for the sake of our compiler we can assume the basic behavior will continue to work unchanged (the value of an instance of fixnum 3 will remain 3). Knowing that we have a literal which will not change can be used for optimizations like constant propagation. ENEBO: This cachedObject thing obviously cannot be used from multiple threads without some safety being added. This probably also is not the fastest code, but it is very simple. It would be really nice to make this side-effect free as well, but this is difficult without adding a level of indirection or pre-caching each value we encounter during construction.
public abstract class ImmutableLiteral extends Operand {
    private Object cachedObject = null;
    @Override
    public boolean hasKnownValue() {
        return true;
    }
    @Override
    public boolean canCopyPropagate() {
        return true;
    }
    
    @Override
    public void addUsedVariables(List<Variablel) {
        /* Do nothing */
    }
    @Override
    public Operand cloneForInlining(InlinerInfo ii) {
        return this;
    }
    
    
Implementing class is responsible for constructing the cached value.
    public abstract Object createCacheObject(ThreadContext context);
    

    
Returns the cached object. If not then it asks class to create an object to cache.
    public Object cachedObject(ThreadContext context) {
        if (!isCached())  = createCacheObject(context);
        
        return ;
    }
 
    
Has this object already been cached?
    public boolean isCached() {
        return  != null;
    }

    
retrieve the live value represented by this immutable literal. An interesting property of knowing something cannot change at compile time is that all information neccesary to construct it is also known at compile time. We don't pre-create these since we don't want to assume the cost of constructing literals which may never be used.
    @Override
    public Object retrieve(ThreadContext contextIRubyObject selfDynamicScope currDynScopeObject[] temp) {
        return cachedObject(context);
    }    
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