[PATCH] Adding a timing option for IR parsing

[Chandler Carruth]

On Thu, Mar 21, 2013 at 8:20 PM, Andrew Trick <atrick at apple.com> wrote:

>
> On Mar 21, 2013, at 7:24 PM, Chandler Carruth <chandlerc at google.com>
> wrote:
>
> FYI, I reverted the patch in r177695 to fix our builds. We check that
> layering violations don't get any worse in our build system.
>
> Fundamentally, the existing layering problem is "worked around" but there
> being no implementation. As long as thats true, all the Support library is
> providing is a text header file. As long as it is only included into source
> files that are part of a library which will eventually get linked with the
> core library, the AsmParser library, and the BitcodeReader library, all is
> well. Including it into a source file in Support makes the layering
> violation actively worse.
>
> I think the correct solution is to do one of two things:
>
> 1) Create a new library which depends on both AsmParser and BitcodeReader
> and which can be used by opt and friends. Put IRReader here.
> 2) Fold AsmParser into the IR library (where AsmWriter already lives). Put
> IRReader into the BitcodeReader library.
>
> I thought about a third option: put both AsmParser and IRReader into the
> BitcodeReader library. But increasingly that seems like a really gross
> layering.
>
>
> I like option #2, but some people might not want to link in the largish
> parser lib.
>

I find this surprising given the relative size of the IR library... But
I've heard the same before. Maybe someone else can provide some clarity on
exactly what the concern is here.


>
> Seems like the IR library should provide a text header IRReader.h. Anyone
> calling it should also link AsmParser and BitcodeReader.  I don't think we
> need IRReader.cpp, but if we did it would be implemented in /IR and linked
> in LLVMCore.
>

If IRReader depends on BitcodeReader, we cannot put it in the IR tree, or
link in its implementation in LLVMCore. That's the the same kind of
layering violation we already have.
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