Yang, Sheng wrote:
>> I have a vague plan for improving decode; basically extend the decode
>> tables to add group decoding. We add a bit to opcode_table and
>> twobyte_table that is set for all instructions which need group
>> decoding. When the bit is set, the rest of the value in opcode_table is
>> interpreted as an index (together with modrm_reg) into a new
>> group_table, so we can have different decoding for such instructions.
>>
>
> I also have tried to propose a table for Grp opcode, but can't find a easy
> way. Using the rest of the value in opcode_table is a good idea, but I'm
> afraid the same value for different group exists, e.g. 0x82(Grp1) and 0xc0
> (Grp2) got the same value as: ByteOp | DstMem | SrcImm | ModRM. If we add
> more factors to this, it would become unclear and more tricky, the table also
> may become larger...
>
> Currently, if we want to using group_table, I think the straightforward way
> is
> better: another big "switch"... The only exception is 1a, and we may use 0
> instead of it.
>
Not sure what you mean. I thought of adding code like
if (c->d & Group) {
c->group = c->d & GroupMask;
// fetch modrm_reg
c->d = group_table[c->group * 8 + modrm_reg];
}
Instruction execution could continue to be in the regular switch, but
the decode flags can be different for every instruction in the group.
--
error compiling committee.c: too many arguments to function
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