Re: x32 psABI draft version 0.2

["Jan Beulich" <JBeulich@novell.com>]

>>> On 17.02.11 at 18:59, "H.J. Lu" <hjl.tools@gmail.com> wrote:
> On Thu, Feb 17, 2011 at 8:11 AM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>> On 17.02.11 at 16:49, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>> On Thu, Feb 17, 2011 at 7:44 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>>>>> > According to Mozilla folks however REL+RELA scheme used by EABI leads
>>>>> > to significandly smaller libxul.so size
>>>>> >
>>>>> > According to http://glandium.org/blog/?p=1177 the difference is about 4-5MB
>>>>> > (out of approximately 20-30MB shared lib)
>>>>>
>>>>> This is orthogonal to x32 psABI.
>>>>
>>>> Understood.  I am just pointing out that x86-64 Mozilla suffers from startup
>>>> problems (extra 5MB of disk read needed) compared to both x86 and ARM EABI
>>>> because x86-64 ABI is RELA only. If x86-64 ABI was REL+RELA like EABI is, we
>>>> would not have this problem here.
>>>>
>>>
>>> If people want to see REL+RELA in x32, they have to contribute codes.
>>
>> That's exactly the wrong way round: First the specification has to allow
>> for (but not require) it, and only then does it make sense to write code.
>>
> 
> No, it has to be supported at least by static linker and dynamic
> linker. Otherwise, no one can use it.

I'm afraid I have to disagree: ELF (and the psABI) is not specific to
a particular OS, and hence it allowing something doesn't mean the
OS ABI may not restrict it. Hence the psABI first has to at least not
forbid something (as it currently does for REL on x86-64), in order
for an implementation of that something to make sense.

Jan