Real Operations

For Real operations code is always generated. This procedure generates code for operations on Real values. If 80×87 instructions are enabled, it converts both expressions to Extended and generates FPU code otherwise it generates code to call system function.

  Procedure GenerateCodeForRealOperations;
  begin
    If Instructions80x87 in StatementCompilerSwitches then
      begin
        LeftExpression.ConvertRealToExtended;
        RightExpression.ConvertRealToExtended;
        GenerateCodeForExtendedOperations;
        Exit;
      end;
    Case Operation of
      Calc_IsEqual..Calc_IsLowerOrEqual,
      Calc_Add,
      Calc_Multiply: If (RightExpression.UsedRegisters <> []) and (LeftExpression.UsedRegisters = []) then
                       ExchangeLeftAndRightExpression;
    end;
    Case RightExpression.UsedRegisters = [] of
      True: begin
              LeftExpression.Calculate;
              LeftExpression.LoadRealExpressionToRegisterSet (rAX_BX_DX);
              RightExpression.Calculate;
              RightExpression.LoadRealExpressionToRegisterSet (rCX_SI_DI);
            end;
      else begin
             RightExpression.Calculate;
             RightExpression.LoadRealExpressionToRegisterSet (rAX_BX_DX);
             GenerateInstruction_TwoBytes (PUSH_DX, PUSH_BX);
             GenerateInstruction_Byte (PUSH_AX);
             LeftExpression.Calculate;
             LeftExpression.LoadRealExpressionToRegisterSet (rAX_BX_DX);
             GenerateInstruction_Byte (POP_CX);
             GenerateInstruction_TwoBytes (POP_SI, POP_DI);
           end;
    end;
    Case Operation of
      Calc_Add:      GenerateInstruction_CALL_FAR (SysProc_RAdd);
      Calc_Subtract: GenerateInstruction_CALL_FAR (SysProc_RSub);
      Calc_Multiply: GenerateInstruction_CALL_FAR (SysProc_RMul);
      Calc_Divide:   GenerateInstruction_CALL_FAR (SysProc_RDiv);
      else begin
             GenerateInstruction_CALL_FAR (SysProc_RCmp);
             LeftExpression.EndIntermediateCodeSubroutine;
             LeftExpression.SetExpressionToBooleanJump (UnsignedConditionalJumpOpCode [Operation]);
             Exit;
           end;
    end;
    LeftExpression.EndIntermediateCodeSubroutine;
  end;