[PATCH] D11612: [lld][ELF2] Apply relocations.

[Denis Protivensky via llvm-commits]

On 08/14/2015 08:46 AM, Simon Atanasyan via llvm-commits wrote:
> On Fri, Aug 14, 2015 at 7:01 AM, Sean Silva <chisophugis at gmail.com> wrote:
>> On Thu, Aug 13, 2015 at 8:42 PM, Rafael Espíndola
>> <rafael.espindola at gmail.com> wrote:
>>> I am *totally* opposed to
>>> *ever* having a YAML test that can be written in assembly.
>>>
>>> If I can understand that entire YAML gunk is:
>>>
>>> foo:
>>> .section bar
>>>          call foo
>>>
>> I like seeing bytes and symbolized ELF spec names. That is what I know best.
>> That is what anybody working on this linker will know. I don't know all the
>> weird corners of gas syntax (+ LLVM extensions apparently), nor would I
>> expect any linker developer to know that. I *would* expect any linker
>> developer to know the symbolic constants (or at least be able to easily
>> google them).
>>
>> The YAML file directly expresses the intent; yes there is lots of "gunk"
>> surrounding it, but any linker developer knows how to skim that based on
>> knowing the meaning of the symbolic constants. Do you find it hard to
>> navigate the YAML files? We can improve the format if necessary if there is
>> a particular pain point or two.
>>
>> To put it another way, every "gas directives" file I see in the test
>> directory, my immediate reaction is wanting to assemble it and readobj it to
>> see what it "actually" is feeding to the linker. I particularly like the
>> YAML because like readobj output, it is telling you pretty straight up what
>> is there. One doesn't need to guess what flags the assembler set on that
>> section, whether a particular relocation kind actually ends up in the
>> output, etc. You just see it immediately in your editor.
> I totally agreed with Sean Silva. The largest number of YAML tests are
> MIPS related.
> Yes, some of them were written in YAML just because at the moment of creation
> llvm-mc did not support all necessary MIPS instruction and directives. Now I
> would write some tests using assembly but only a few of them. Does everybody
> know MIPS assembly directives? Otherwise it will be difficult to investigate/fix
> failed tests because. YAML is more verbose but clear and understandable.
>
> And as to me a real nightmare is using binary inputs in linker's tests.
> If such tests failed I have to parse the binary using objdump/readobj tools
> to understand what happens.
>
For general ELF linking logic YAML format should be enough, as it's 
possible to grab assembly code by yaml2obj+objdump' ing a YAML script.
But as for backends for particular processor architectures, I'd like to 
have YAML + C reference code to simplify understanding
of how some high-level constructs get translated considering given ABI.