BadWhileExpressionCompiler.cs

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using BadScript2.Parser.Expressions.Block.Loop;
using BadScript2.Runtime.Objects;
 
namespace BadScript2.Runtime.VirtualMachine.Compiler.ExpressionCompilers.Block;
 
public class BadWhileExpressionCompiler : BadExpressionCompiler<BadWhileExpression>
{
    public override void Compile(BadExpressionCompileContext context, BadWhileExpression expression)
    {
        int start = context.InstructionCount;
        context.Compile(expression.Condition);
        int endJump = context.EmitEmpty();
        int loopScopeStart = context.InstructionCount;
        //Break And continue pointers are relative to the "CreateScope" instruction
        //If break instruction is encountered
        //  Jump to loopScopeStart + offset to after loop(the destroy scope instruction is omitted because the vm handles the scopes)
        context.Emit(
            BadOpCode.CreateScope,
            expression.Position,
            "WhileScope",
            BadObject.Null,
            BadScopeFlags.Breakable | BadScopeFlags.Continuable
        );
        int setBreakInstruction = context.EmitEmpty();
        int setContinueInstruction = context.EmitEmpty();
        context.Compile(expression.Body);
        context.Emit(BadOpCode.DestroyScope, expression.Position);
        //Jump back up to the loop condition
        int continueJump = context.InstructionCount;
        context.Emit(BadOpCode.JumpRelative, expression.Position, start - context.InstructionCount - 1);
 
        //Set the end jump to the end of the loop
        context.ResolveEmpty(endJump, BadOpCode.JumpRelativeIfFalse, expression.Position, context.InstructionCount - endJump - 1);
        //address to the end of the loop(relative to the create scope instruction)
        context.ResolveEmpty(setBreakInstruction, BadOpCode.SetBreakPointer, expression.Position, context.InstructionCount - loopScopeStart - 1);
        //Address to start of the condition(relative to the start of the loop)
        context.ResolveEmpty(setContinueInstruction, BadOpCode.SetContinuePointer, expression.Position, continueJump - loopScopeStart - 1);
    }
}