Re: [PATCH-for-8.0 4/7] hw/mips/bootloader: Implement nanoMIPS LUI opcode

[Jiaxun Yang]

> 2022年12月10日 16:01，Philippe Mathieu-Daudé <philmd@linaro.org> 写道：
> 
> On 10/12/22 16:54, Philippe Mathieu-Daudé wrote:
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>  hw/mips/bootloader.c | 29 ++++++++++++++++++++++++++---
>>  1 file changed, 26 insertions(+), 3 deletions(-)
>> diff --git a/hw/mips/bootloader.c b/hw/mips/bootloader.c
>> index 7f7d938f2e..997e74ee52 100644
>> --- a/hw/mips/bootloader.c
>> +++ b/hw/mips/bootloader.c
>> @@ -120,11 +120,34 @@ static void bl_gen_jalr(void **p, bl_reg rs)
>>      bl_gen_r_type(p, 0, rs, 0, BL_REG_RA, 0, 0x09);
>>  }
>>  +static void bl_gen_lui_nm(void **ptr, bl_reg rt, uint32_t imm20)
>> +{
>> +    uint16_t *p = (uint16_t *)*ptr;
>> +    uint32_t insn = 0;
> 
> Hmm we should check if imm20 fits in 20-bit.

Perhaps it will be easier to use 48bit addiu instruction to generate LI?

Thanks
- Jiaxun

> 
>> +    insn = deposit32(insn, 26, 6, 0b111000);
>> +    insn = deposit32(insn, 21, 5, rt);
>> +    insn = deposit32(insn, 12, 9, extract32(imm20, 12, 9));
>> +    insn = deposit32(insn, 2, 10, extract32(imm20, 21, 10));
>> +    insn = deposit32(insn, 0, 1, sextract32(imm20, 31, 1));
>> +
>> +    stw_p(p, insn >> 16);
>> +    p++;
>> +    stw_p(p, insn >> 0);
>> +    p++;
>> +
>> +    *ptr = p;
>> +}