[lld] r222983 - [Core] Add flag to check if RoundTripPasses need to be run.

[Rui Ueyama]

I learned we are using env command in Clang tests like this.

RUN: env FOO=bar clang ...

It seems we could do the same thing to disable the tests per-test basis.

RUN: env LLD_ROUNDTRIP_TEST= lld ...

On Mon, Dec 1, 2014 at 2:20 PM, Rui Ueyama <ruiu at google.com> wrote:

> I think that's arguable if that's considered as information lost. After an
> atom is written to a new Native file and reloaded, it gets a new file name
> because it was actually read from a different file. If a compiler outputs
> an object file in Native format, it's the file name of an atom read from
> the file.
>
> On Mon, Dec 1, 2014 at 2:14 PM, Shankar Easwaran <shankare at codeaurora.org>
> wrote:
>
>> On 12/1/2014 4:02 PM, Rui Ueyama wrote:
>>
>>> On Mon, Dec 1, 2014 at 1:48 PM, Nick Kledzik <kledzik at apple.com> wrote:
>>>
>>>  On Dec 1, 2014, at 12:34 PM, Rui Ueyama <ruiu at google.com> wrote:
>>>>
>>>> That sounds like we really need a new property of Atom.
>>>>
>>>> 1. If we run LLD in Release build, the roundtrip passes don't run, so
>>>> everything works fine.
>>>> 2. If we run LLD in Debug build (and from the unit tests), the
>>>> information
>>>> is dropped during the round-trip conversion, and it fails.
>>>> 3. RoundTrip tests should't drop any information.
>>>>
>>>> 2 and 3 conflicts.
>>>>
>>>>
>>>> I have a different view.
>>>>
>>>> I think of those Passes as a quick way to exercise the YAML and native
>>>> formats.  The mechanism is as if you went through the test cases and
>>>> added
>>>> a line which ran “ld -r” to merge all input files into one file, then
>>>> ran
>>>> the rest of the test with that merged input file.  That works everywhere
>>>> except in tests that care about the name of the input file (which is now
>>>> changed).  So, for those cases you would not do the merge step.  But
>>>> since
>>>> the round trip is implicit, there is no way to turn it off.  Shankar is
>>>> adding a way to turn it off.
>>>>
>>>>  That doesn't sounds like a different view.
>>>
>>> If a test fails because of the difference of an input file name, not
>>> because the round-trip conversion drops some information, we should
>>> disable
>>> the round-trip test only for that test. Now I feel I understood your
>>> suggestion in a different thread. Is there any way to override the
>>> environment variable in the lit test? Does it allow us to write RUN:
>>> LLD_ROUNDTRIP_TEST=0 lld <args here> ?
>>>
>>
>> The filename information of the Atom is lost in the Native format.
>>
>> Gnu flavor needs the filename whenever the user uses a linker script (or)
>> the user decides to know the memory map of the image.
>>
>> So this is needed almost all the time.
>>
>>
>> Shankar Easwaran
>>
>> --
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
>> by the Linux Foundation
>>
>>
>
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