Re: [RFC PATCH 2/8] riscv: Generate payload scripts

[Richard Henderson]

On 5/19/20 7:37 PM, LIU Zhiwei wrote:
> On 2020/5/12 1:40, Richard Henderson wrote:
>> On 4/30/20 12:21 AM, LIU Zhiwei wrote:
>>> +    # sequence of li rd, 0x1234567887654321
>>> +    #
>>> +    #  0:   002471b7                lui     rd,0x247
>>> +    #  4:   8ad1819b                addiw   rd,rd,-1875
>>> +    #  8:   00c19193                slli    rd,rd,0xc
>>> +    #  c:   f1118193                addi    rd,rd,-239 # 0x246f11
>>> +    # 10:   00d19193                slli    rd,rd,0xd
>>> +    # 14:   d9518193                addi    rd,rd,-619
>>> +    # 18:   00e19193                slli    rd,rd,0xe
>>> +    # 1c:   32118193                addi    rd,rd,801
>> You don't really need to use addiw.  Removing that special case would really
>> simplify this.
> I think I don't get it. Do you mean that the immediate will not be 64 bit?

Well, mostly the immediate will be small, actually.  But the interface must
support 64-bit immediates.

I'm saying that for this computation,

        lui
        addi
        slli
        addi
        ...

is the same.  You don't *have* to use addiw.


r~