Qing Zhao <qing.z...@oracle.com> writes:
> Last question, in the following code portion:
>
> /* Now we get a hard register set that need to be zeroed, pass it to
> target to generate zeroing sequence. */
> HARD_REG_SET zeroed_hardregs;
> start_sequence ();
> zeroed_hardregs = targetm.calls.zero_call_used_regs (need_zeroed_hardregs);
> rtx_insn *seq = get_insns ();
> end_sequence ();
> if (seq)
> {
> /* emit the memory blockage and register clobber asm volatile. */
> rtx barrier_rtx = expand_asm_reg_clobber_blockage (zeroed_hardregs);
>
> /* How to insert the barrier_rtx before "seq"???. */
> ??????
> emit_insn_before (barrier_rtx, seq); ??????
>
> emit_insn_before (seq, ret);
>
> /* update the data flow information. */
>
> df_set_bb_dirty (BLOCK_FOR_INSN (ret));
> }
>
> In the above, how should I insert the barrier_rtx in the beginning of “seq” ?
> And then insert the seq before ret?
> Is there special thing I need to take care?
Easiest way is just to insert both of them before ret:
emit_insn_before (barrier_rtx, ret);
emit_insn_before (seq, ret);
Note that you shouldn't need to mark the block containing the
return instruction as dirty: the emit machinery should do that
for you. But it might be necessary to mark the exit block
(EXIT_BLOCK_PTR_FOR_FN (cfun)) as dirty because of the new
liveness information -- I'm not sure.
Thanks,
Richard
