LLD: Move RoundTrip tests behind a flag

[Shankar Easwaran]

LGTM.

On 3/19/2014 6:38 PM, Rui Ueyama wrote:
> Looks like we agreed that this should be enabled only when some 
> environment variable (maybe LLD_ENABLE_ROUNDTRIP_TEST?) is set, ok?
>
>
> On Wed, Mar 19, 2014 at 4:31 PM, Shankar Easwaran 
> <shankare at codeaurora.org <mailto:shankare at codeaurora.org>> wrote:
>
>     On 3/19/2014 5:44 PM, Nick Kledzik wrote:
>
>         On Mar 19, 2014, at 3:38 PM, Rui Ueyama <ruiu at google.com
>         <mailto:ruiu at google.com>> wrote:
>
>             It is proved that RoundTripNative and RoundTripYAML are
>             good harnesses to guarantee there's no information loss
>             when an object is converted to/from native/YAML formats.
>             However, it makes LLD *extremely* slow when linking
>             non-toy programs.
>
>             If RoundTrip tests are enabled, LLD takes about 10
>             *minutes* to link itself on my Linux box. My machine is
>             3.5GHz Xeon. The result of gprof on LLD linking
>             llvm-tblegen shows that 77.8% of time was consumed by
>             RoundTripYAMLPass::perform() and 16.6% by
>             RoundTripNativePass::perform(). It means RoundTrip tests
>             are the dominant factor.
>
>             I couldn't even run LLD linking LLD with profiling enabled
>             because it was too slow that I couldn't wait it to finish.
>
>             This is not an acceptable performance penalty even for
>             debug build. I think we should move the feature behind a
>             flag and enable it only for tests.
>
>             Any objections?
>
>         Sounds good.  But, how can we set it up so that all tests
>         (including tests added later) will get the round trip passes
>         by default?  Is there some environment variable that the LIT
>         harness sets up that the driver can detect and run those
>         passes by default?
>
>     I like the environment variable idea too.
>
>
>     --
>     Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>     hosted by the Linux Foundation
>
>


-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation

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