/**
* This method runs through the expression in order to generate the corresponding assembly code.
* At the end of the run, the result is always stored in Register.RAX
*/
public StringBuffer handleExpression(Expression e, Context context) throws Exception {
StringBuffer sb = new StringBuffer();
String lastReg;
if (Parser.DEBUG) System.out.println("\nHandling expression: \"" + this.toString() + "\"");
if (this.right == null) {
// Handle leaf
if (this instanceof Variable) {
if (Parser.DEBUG) System.out.println("\tVariable caught: " + ((Variable) this).getValue());
sb = ExpressionHelper.handleVariable(sb, (Variable) this, Register.RAX, context);
} else if (this instanceof FunctionCall) {
if (Parser.DEBUG)
System.out.println("\tFunction-call caught: " + ((FunctionCall) this).getTag());
sb = ExpressionHelper.handleFunctionCall(sb, (FunctionCall) this, context);
}
return sb;
}
sb.append(this.left.handleExpression(e, context));
if (this.flag != null && this.flag.equals(Flag.UMINUS))
sb.append(ExpressionHelper.asm(Assembly.NEG, Register.RAX));
if (this.right.op != null && this.right.priority == false) {
// Handle expression with three or more operands
if (this.right.left.priority) {
// Handle priority expression first (parentheses).
this.right.left.priority = false;
sb.append(context.virtualPush(Register.RAX.toString()));
sb.append(this.right.left.handleExpression(e, context));
sb.append(context.virtualPop(Register.RDX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RAX, Register.RDX);
sb.append(context.virtualPush(Register.RAX.toString()));
sb.append(this.right.right.handleExpression(e, context));
sb.append(context.virtualPop(Register.RDX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.right.op, Register.RAX, Register.RDX);
} else if (ExpressionHelper.getPrecedence(this.op.toString())
> ExpressionHelper.getPrecedence(this.right.op.toString())) {
// Handle operators of higher precedence first.
if (this.right.left instanceof Variable)
sb =
ExpressionHelper.handleVariable(
sb, (Variable) this.right.left, Register.RDX, context);
else {
sb.append(ExpressionHelper.asm(Assembly.MOV, Register.RAX, Register.RDX));
sb = ExpressionHelper.handleFunctionCall(sb, (FunctionCall) this.right.left, context);
}
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RDX, Register.RAX);
sb.append(context.virtualPush(Register.RAX.toString()));
sb.append(this.right.right.handleExpression(e, context));
sb.append(context.virtualPop(Register.RDX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.right.op, Register.RAX, Register.RDX);
} else {
sb.append(context.virtualPush(Register.RAX.toString()));
sb.append(this.right.handleExpression(e, context));
sb.append(ExpressionHelper.asm(Assembly.MOV, Register.RAX, Register.RDX));
sb.append(context.virtualPop(Register.RAX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RAX, Register.RDX);
}
} else {
// Handle simple node (l op r)
if (this.right.priority) {
sb.append(context.virtualPush(Register.RAX.toString()));
sb.append(this.right.handleExpression(e, context));
sb.append(context.virtualPop(Register.RDX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RAX, Register.RDX);
} else if (this.right instanceof Variable) {
if (((Variable) this.right).getValue() instanceof Integer) {
if (this.right.flag != null && this.right.flag.equals(Flag.UMINUS))
sb =
ExpressionHelper.handleOperation(
sb, this.op, "$-" + ((Variable) this.right).getValue());
else
sb =
ExpressionHelper.handleOperation(
sb, this.op, "$" + ((Variable) this.right).getValue());
} else {
if (((Variable) this.right).index != null)
sb.append(context.virtualPush(Register.RAX.toString()));
sb = ExpressionHelper.handleVariable(sb, (Variable) this.right, Register.RDX, context);
if (((Variable) this.right).index != null) {
sb.append(ExpressionHelper.asm(Assembly.MOV, Register.RAX, Register.RDX));
sb.append(context.virtualPop(Register.RAX.toString()));
}
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RDX, Register.RAX);
}
} else if (this.right instanceof FunctionCall) {
sb.append(context.virtualPush(Register.RAX.toString()));
sb = ExpressionHelper.handleFunctionCall(sb, (FunctionCall) this.right, context);
sb.append(context.virtualPop(Register.RDX.toString()));
sb = ExpressionHelper.handleOperation(sb, this.op, Register.RAX, Register.RDX);
sb.append(ExpressionHelper.asm(Assembly.MOV, Register.RAX, Register.RDX));
}
}
return sb;
}
