Re: [x32] Allow R_X86_64_64

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Aug 12, 2011 at 6:59 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>> On 12.08.11 at 15:22, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>> On Fri, Aug 12, 2011 at 6:17 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>>> On 12.08.11 at 14:09, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>>> On Fri, Aug 12, 2011 at 12:30 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>>>>> On 12.08.11 at 06:37, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>>>>> On Mon, Aug 1, 2011 at 3:15 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> It turns out that x32 needs R_X86_64_64. ?One major reason is
>>>>>>> the displacement range of x32 is -2G to +2G. ?It isn't a problem
>>>>>>> for compiler since only small model is required for x32.
>>>>>>>
>>>>>>> However, to address 0 to 4G directly in assembly code, we have
>>>>>>> to use R_X86_64_64 with movabs. ?I am checking the follow patch
>>>>>>> into x32 psABI to allow R_X86_64_64.
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> X32 ?Linker should treats R_X86_64_64 as R_X86_64_32
>>>>>> zero-extended to 64bit for output. ?I will update x32 psABI with
>>>>>
>>>>> I'm sorry to say that, but the situation about x32 seems to be
>>>>> getting worse with each change you do, every time again
>>>>> revolving around mixing up ABI specification and a particular
>>>>> implementation thereof.
>>>>>
>>>>> Here, if you need something zero-extended (though I can't see
>>>>> why you would), then you should use a new relocation type. As
>>>>> pointed out before, there are valid possible uses of R_X86_64_64
>>>>> that would require the semantics of x86-64.
>>>>>
>>>>
>>>> When does x32 need the semantics of x86-64 for R_X86_64_64?
>>>
>>> When referencing an assembler or linker defined constant that
>>> exceeds 32-bit in width. Given that this is a 64-bit architecture
>>> with 32-bit addresses, at least I would expect such to work.
>>>
>>
>> Yes, it should work just fine for x32 by zero-extending 32bit
>> address to 64bit.
>
> For a constant that has more than 32 significant bits???
>

Can you give me an example in assembly code?


-- 
H.J.