Re: [Qemu-devel] [PATCH v3 07/20] tcg-arm: Fold epilogue into INDEX_op_exit_tb

[Peter Maydell]

On 28 March 2013 15:32, Richard Henderson <address@hidden> wrote:
> The epilogue on ARM is one pop instruction, that pops the return
> address into PC.  Avoid the jump to jump for this case.  Use the
> standard movi32 routine for loading the return value if it's easy.

> @@ -2025,8 +2023,7 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>      tcg_out_mov(s, TCG_TYPE_PTR, TCG_AREG0, tcg_target_call_iarg_regs[0]);
>
>      tcg_out_bx(s, COND_AL, tcg_target_call_iarg_regs[1]);
> -    tb_ret_addr = s->code_ptr;
>
>      /* ldmia sp!, { r4 - r12, pc } */
> -    tcg_out32(s, (COND_AL << 28) | 0x08bd9ff0);
> +    tb_pop_ret = (COND_AL << 28) | 0x08bd9ff0;
>  }

Why are we using a variable when it's always constant?

Also, please add a comment to the bottom of the qemu_prologue()
saying something like

/* We never return here; we always return directly from generated
 * code to our caller.
 */

thanks
-- PMM