Re: [Qemu-devel] [PATCH] target-tilegx: Support iret instruction and related special registers

[Richard Henderson <rth@twiddle.net>]

On 09/28/2015 03:06 PM, gang.chen.5i5j@gmail.com wrote:
> From: Chen Gang <gang.chen.5i5j@gmail.com>
>
> Acording to the __longjmp tilegx libc implementation, and reference from
> tilegx ISA document, we can left iret instruction empty. The related
> code is below:
>
>    ENTRY (__longjmp)
>           FEEDBACK_ENTER(__longjmp)
>
>    #define RESTORE(r) { LD r, r0 ; ADDI_PTR r0, r0, REGSIZE }
>           FOR_EACH_CALLEE_SAVED_REG(RESTORE)
>
>           {
>            LD r2, r0       ; retrieve ICS bit from jmp_buf
>            movei r3, 1
>            CMPEQI r0, r1, 0
>           }
>
>           {
>            mtspr INTERRUPT_CRITICAL_SECTION, r3
>            shli r2, r2, SPR_EX_CONTEXT_0_1__ICS_SHIFT
>           }
>
>           {
>            mtspr EX_CONTEXT_0_0, lr
>            ori r2, r2, RETURN_PL
>           }
>
>           {
>            or r0, r1, r0
>            mtspr EX_CONTEXT_0_1, r2
>           }
>
>           iret
>
>           jrp lr
>
> So can let busybox sh run correctly.
>
> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> ---
>   target-tilegx/cpu.h       | 2 ++
>   target-tilegx/translate.c | 8 +++++++-
>   2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/target-tilegx/cpu.h b/target-tilegx/cpu.h
> index 4b05cd2..02e1a18 100644
> --- a/target-tilegx/cpu.h
> +++ b/target-tilegx/cpu.h
> @@ -54,6 +54,8 @@ enum {
>       TILEGX_SPR_CRITICAL_SEC = 1,
>       TILEGX_SPR_SIM_CONTROL = 2,
>       TILEGX_SPR_EX_CONTEXT_1 = 3,
> +    TILEGX_SPR_EX_CONTEXT_0_0 = 4,
> +    TILEGX_SPR_EX_CONTEXT_0_1 = 5,

Don't add spr's you're not going to use.


r~