org.jruby.ir.instructions.BreakInstr Maven / Gradle / Ivy

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package org.jruby.ir.instructions;

import org.jruby.ir.IRVisitor;
import org.jruby.ir.IRScope;
import org.jruby.ir.Operation;
import org.jruby.ir.interpreter.IRBreakJump;
import org.jruby.ir.operands.Operand;
import org.jruby.ir.operands.Variable;
import org.jruby.ir.transformations.inlining.InlinerInfo;
import org.jruby.runtime.Block;
import org.jruby.runtime.DynamicScope;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;

import java.util.Map;

// NOTE: breaks that jump out of while/until loops would have
// been transformed by the IR building into an ordinary jump.
//
// A break instruction is not just any old instruction.
// Like a return instruction, it exits a scope and returns a value
//
// Ex: (1..5).collect { |n| break if n > 3; n } returns nil
//
// All break instructions like returns have an associated return value
// In the absence of an explicit value to return, nil is returned
//
// Ex: (1..5).collect { |n| break "Hurrah" if n > 3; n } returns "Hurrah"
//
// But, whereas a return exits the innermost method it is in,
// a break only exits out of the innermost non-method scope it is in.
// So, an exposed/naked break inside a method throws an exception!
//
// def foo(n); break if n > 5; end; foo(100) will throw an exception
//
public class BreakInstr extends Instr {
    private final IRScope scopeToReturnTo;
    protected Operand returnValue;

    public BreakInstr(Operand rv, IRScope s) {
        super(Operation.BREAK);
        this.scopeToReturnTo = s;
        this.returnValue = rv;
    }
    
    public Operand[] getOperands() {
        return new Operand[] { returnValue };
    }

    @Override
    public Instr cloneForInlining(InlinerInfo ii) {
        return new BreakInstr(returnValue.cloneForInlining(ii), scopeToReturnTo);
    }

    @Override
    public Instr cloneForInlinedScope(InlinerInfo ii) {
        if (ii.getInlineHostScope() == scopeToReturnTo) {
            // If the break got inlined into the scope we had to break to, replace the break
            // with a COPY of the break-value into the call's result var.
            // Ex: v = foo { ..; break n; ..}.  So, "break n" is replaced with "v = n"
            // The CFG for the closure will be such that after break, control goes to the 
            // scope exit block.  So, we know that after the copy, we'll continue with the
            // instruction after the call.
            Variable v = ii.getCallResultVariable();
            return (v == null) ? null : new CopyInstr(v, returnValue.cloneForInlining(ii));
        } else {
            return cloneForInlining(ii);
        }
    }

    @Override
    public Object interpret(ThreadContext context, DynamicScope currDynScope, IRubyObject self, Object[] temp, Block block) {
        throw IRBreakJump.create(scopeToReturnTo, returnValue.retrieve(context, self, currDynScope, temp));
    }

    @Override
    public String toString() {
        return getOperation() + "(" + returnValue + (scopeToReturnTo == null ? "" : ", " + scopeToReturnTo) + ")";
    }

    @Override
    public void simplifyOperands(Map valueMap, boolean force) {
        returnValue = returnValue.getSimplifiedOperand(valueMap, force);
    }

    @Override
    public void visit(IRVisitor visitor) {
        visitor.BreakInstr(this);
    }
}