[LLVMdev] registerSize on X86 confused?

Craig Topper
Wed, 02 Apr 2014 00:22:45 -0000

I looked at this briefly, I think it causes some mistakes that get reversed
later in fixupReg. The disassembler design is a bit of a mess with regards
to prefixes and operand size.


On Tue, Apr 1, 2014 at 4:43 PM, Jun Koi <junkoi2004 at gmail.com> wrote:

>
>
>
> On Mon, Mar 31, 2014 at 11:48 PM, Jun Koi <junkoi2004 at gmail.com>
wrote:
>
>> Hi,
>>
>> In file X86DisassemblerDecoder.c, we have function readPrefixes() with
>> below code:
>>
>> .....
>>   } else if (insn->mode == MODE_32BIT) {
>>     insn->registerSize       = (hasOpSize ? 2 : 4);
>>     insn->addressSize        = (hasAdSize ? 2 : 4);
>>     insn->displacementSize   = (hasAdSize ? 2 : 4);
>>     insn->immediateSize      = (hasOpSize ? 2 : 4);
>>   }
>> ....
>>
>> This is confused to me: so we have registerSize to be either 2 or 4
bytes.
>> But we might have instruction like:
>>
>>      adc    al, 0x89
>>
>> This case we should have registerSize = 1 for AL. So is this a bug, or
I
>> am misunderstanding the meaning of this "registerSize" ??
>>
>>
> any help please?
>
> thanks.
>
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--
~Craig
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