generate RTL sequence

[daniel tian]

Hi,
    I have a problem about RTL sequence.
    If I wanna generate the RTL in sequence, and don't let gcc to schedule them.
    Like the following(all the variable is rtx):

    emit_insn(reg0,  operands[0]);
    emit_insn(reg1,  reg0);
    emit_insn(operands[0],  reg1);

    But gcc will will reorder the three rtl in optimization.
    I just wanna the those rtl in one block as a unit, don't let the
gcc disrupt the sequence.
    How can I do it?

    By the way, what do the function start_sequence and end_sequence do.
    I type to call those functions in my prologue and epilogue in my
porting back end. but
     cc1 will crash.  I need to bind some kind of rtl, and make them
stay the sequence as generated.

   Thanks for your guys.

                                         daniel.tian