[PATCH] LLD: Remove YAML/Native round-trip passes

Rui Ueyama ruiu at google.com
Fri Feb 20 14:13:01 PST 2015


Committed as r230069.

On Thu, Feb 19, 2015 at 6:14 PM, Rui Ueyama <ruiu at google.com> wrote:

> On Thu, Feb 19, 2015 at 5:50 PM, Rafael EspĂ­ndola <
> rafael.espindola at gmail.com> wrote:
>
>> On 19 February 2015 at 19:41, Michael Spencer <bigcheesegs at gmail.com>
>> wrote:
>> > On Wed, Feb 11, 2015 at 4:37 PM, Rui Ueyama <ruiu at google.com> wrote:
>> >> I found that Writing and reading Native files from YAML reader is
>> actually
>> >> tricky. Readers generally don't need a linking context, but writers
>> do. So
>> >> it's not easy to call a writer from a reader. Seems it needs a plumbing
>> >> work.
>> >>
>> >> Then I tried to convert a YAML file to Native using yaml2obj
>> -format=native.
>> >> yaml2obj didn't actually support Native format because Native format
>> lives
>> >> only in LLD. Yet it's intended to be an alternative, hopefully better
>> object
>> >> file format, it's not supported by anyone except the linker. There's no
>> >> consumer producing a file in that file format.
>> >
>> > We haven't taught clang to produce it yet because the format isn't
>> > finalized. The performance gain from it is still rather large, and I
>> > feel it's an important feature.
>>
>> Please note that we don't have evidence of this yet.
>>
>> I would be very opposed to adding a new file format to llvm proper until
>>
>> * lld is production quality
>> * lld is as fast as gold on ELF
>> * there is experimental evidence that a new format would make it even
>> faster without compromising its ability to report errors.
>>
>
> I agree with all the points. If we eventually think that we need a new
> file format for speed, the current native file format needs to be evaluated
> to see if it's suitable for that purpose, along with other points such as
> extendability of file format, complexity, etc.
>
> For now let me go with this patch to unblock stuffs.
>
> Thank you for reviewing.
>
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