public override void BranchIf(bool sense, Label target)
{
var f=FuncBuilder.Instance;
var emitter=CodeGenerator.Emitter;
var declarer=f.Declare;
using(f.OpenScope("compare")) {
var lhsTemp=declarer.Int("lhs");
var rhsTemp=declarer.Int("rhs");
var lhsResult=lhs.EvaluateTo(lhsTemp);
var rhsResult=rhs.EvaluateTo(rhsTemp);
var lhsReg=lhsResult.ToRegister(f.Scratch0);
var rhsRegOrByte=rhsResult.ToRegisterOrByte(f.Scratch1);
if(rhsRegOrByte.IsRegister) {
emitter.Emit(Format4OpCode.CMP, lhsReg, rhsRegOrByte.Register);
} else {
emitter.Emit(Format3OpCode.CMP, lhsReg, rhsRegOrByte.Byte);
}
var instructionToUse=sense ? branchOpCode : inverseOpCode;
var address=target.GetLabelAddressBestEffort();
emitter.Emit(instructionToUse, address);
}
}
public static void UnconditionalBranchTo(Label target)
{
var emitter=CodeGenerator.Emitter;
var targetAddress=target.GetLabelAddressBestEffort();
var caddr=emitter.CurrentAddress;
//branch to next instruction or branch to self cause this instruction to be elided
//why: in phase N, a needless branch will look like a branch to the next instruction,
// but in phase N+1 it will look like a branch to self
if(targetAddress==caddr || targetAddress==caddr+2) {
Debug.Print("<branch to next instruction removed>");
} else {
emitter.Emit(Format18OpCode.B, targetAddress);
}
}