[llvm-commits] Proof of concept patch for unifying the .s/ELF emission of .ARM.attributes

[Jason Kim]

On Mon, Oct 11, 2010 at 2:48 PM, Jim Grosbach <grosbach at apple.com> wrote:
> Looks OK to me. Please commit!

Thanks Jim!
Comitted as r116257.

Here are two more follow on patches.

arm-mc-elf-s06-elfdump.patch modifies elf-dump script.
It adds a --hex mode for printing all numbers to hex format.
AFAIK, elf-dump output without --hex has remained the same.

The second patch arm-mc-elf-s06.patch changes finally adds enough code to
directly test ARM/MC/ELF/.o emission.
The newly added test passes but the resulting ELF is by no means correct.
It is a simple step in the right direction.

As always, feedback/corrections are very welcome.

-jason


>
> On Oct 11, 2010, at 11:28 AM, Jason Kim wrote:
>
>> Hi everyone, please find enclosed updated version of arm-mc-elf-s05.patch.
>>
>> On Mon, Oct 11, 2010 at 10:39 AM, Jason Kim <jasonwkim at google.com> wrote:
>>> On Mon, Oct 11, 2010 at 9:20 AM, Jim Grosbach <grosbach at apple.com> wrote:
>>>> Hi Jason,
>>>>
>>>> Glad to see this making progress. Here's a bit of general feedback. I'm not an expert on Linux ELF, so I can't really comment on that aspect of things, though.
>>>>
>>>>>  namespace ARMBuildAttrs {
>>>>>    enum AttrType {
>>>>> +    // For the .cpu asm construct
>>>>> +    ARM_CPU,
>>>>> +    // Rest correspond to ELF/.ARM.attributes
>>>>>      File                      = 1,
>>>>>      Section                   = 2,
>>>>>      Symbol                    = 3,
>>>>
>>>>
>>>> Is this new attr distinct from the ones already there for the CPU? CPU_name, in particular, seems a likely candidate. It's hard to tell since the uses of the others don't appear to be implemented yet. In any case, if a new attr does need to be added, it should be consistent with the rest of them. No prefix, and just add the value onto the end (i.e., "Cpu = 71") of the list.
>>>
>>> All of the other enums in the ARMBuildAttrs are specific part of (i.e.
>>> can appear as markers in) the .ARM.attributes section.
>>> The new one I added correspond to the .cpu asm attr, which translates
>>> into one or more sequence of CPU_NAME, CPU_ARCH ... in the actual ELF
>>> section, so I needed a way to get that done.
>>> There is no neat correspondence between the asm attrs and what goes
>>> into the .ARM.attributes. Certainly not for the .cpu attribute (its
>>> one to many)
>>>
>>
>> Jim, it turns out that the bulk of the attr emission is driven by a
>> bunch of bool flags from TargetMachine.
>> The individual ARMBuildAttrs::AttrType flags are not selected individually,
>> so there wasn't a real use for the llvm style switch except for the
>> new flag I added.  (please see new comments in patch)
>>
>> <cut>
>>>
>>> p.s. I have another patch waiting for this to land - I will be adding
>>> just enough to get a basic two instruction function (thanks for new
>>> scaffolding on EncodeInstuction()  Jim!)  output as ELF .o, and be
>>> somewhat sane -
>>> i.e. ARM/MC/ELF hello world ("misspelled, and broken" but at least it
>>> will be a start. :-)
>>>
>>>
>>>>
>>>> Regards,
>>>>
>>>>  Jim
>>>>
>>>>
>>>>
>>>> On Oct 7, 2010, at 8:54 PM, Jason Kim wrote:
>>>>
>>>>> Second set of ARM/MC/ELF changes.
>>>>>
>>>>> Added ARM specific ELF section types.
>>>>> Added AttributesSection to ARMElfTargetObject
>>>>> First step in unifying .cpu assembly tag with ELF/.o
>>>>> llc now asserts on actual ELF emission on -filetype=obj :-)
>>>>>
>>>>> Feedback, please!
>>>>>
>>>>> Thanks for reading!
>>>>>
>>>>> -Jason
>>>>> <arm-mc-elf-s05.patch>
>>>>
>>>>
>>>
>>
>> Unless there is strong objection, I'd like to land this patch soon
>> (today if possible).
>> Thanks for reading!!
>>
>> -jason
>> <arm-mc-elf-s05.patch2>
>
>

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