[PATCH] [PM] Create a separate library for high-level pass management code.

[Pete Cooper]

> On Mar 5, 2015, at 3:02 PM, Chandler Carruth <chandlerc at google.com> wrote:
> 
> 
> On Thu, Mar 5, 2015 at 3:00 PM, Pete Cooper <peter_cooper at apple.com <mailto:peter_cooper at apple.com>> wrote:
>> On Mar 5, 2015, at 2:56 PM, Chandler Carruth <chandlerc at google.com <mailto:chandlerc at google.com>> wrote:
>> 
>> 
>> On Thu, Mar 5, 2015 at 2:51 PM, Pete Cooper <peter_cooper at apple.com <mailto:peter_cooper at apple.com>> wrote:
>>> On Mar 5, 2015, at 2:47 PM, Chandler Carruth <chandlerc at google.com <mailto:chandlerc at google.com>> wrote:
>>> 
>>> 
>>> On Thu, Mar 5, 2015 at 2:46 PM, Pete Cooper <peter_cooper at apple.com <mailto:peter_cooper at apple.com>> wrote:
>>> Yeah, I agree that layering is an issue.
>>> 
>>> The current pass code is in lib/IR, which I think is libCore.  There’s no fundamental reason why your code couldn’t also live there right now.  Its linked against everything you mentioned already.
>>> 
>>> Wait, you've lost me.
>> I’m talking about what if you didn’t create a new library.  I think you’re talking about the relationship between the new libPasses and other libraries.  Otherwise i’m lost too :)
>> 
>> I was saying that if you didn’t create a new library, then I assumed the new PM code could live in libCore next to the current PM code.  And then everything just depends on libCore as they currently do.
>> 
>> No no, that's the problem. Everything depends on libCore. Including libTransforms, libTarget, etc.
>> 
>> the code i've got in Passes right now depends on code in the target library and in the transforms and analysis library. It can't do that from libCore without creating a cycle.
> Ah, i see.  Ouch!
>> 
>> So we have:
>> 
>> parsePassPipeline -> SROA (libTransforms) -> PassManager (IR / Core)
>> 
>> If we put parsePassPipeline in Core, we form a cycle.
> Gotcha.
> 
> So how much of this is going to be optional?  If I create a dylib, can I opt out of parsePassPipeline (export list probably), and therefore not have to link all the passes?  I don’t want to have to carry around passes I know I don’t need.
> 
> All of this is optional.
Great!  Thanks.
> 
> The Passes library contains code to aggregate passes in a useful way. If you define your pass pipeline, you shouldn't need this at all.
I like the sound of that.  The current system is way too heavyweight when I know the pipeline I want.

Then my barrage of questions is compete :)

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