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Chandler Carruth

2012-Dec-17 12:47 UTC

[LLVMdev] LoopPass doFinalization() called multiple times per program?

On Sun, Dec 16, 2012 at 7:23 AM, Duncan Sands <baldrick at free.fr> wrote:
> Hi Stephen,
>
>
> On 13/12/12 18:58, Stephen McGruer wrote:
>
>> I'm wondering if the documentation for LoopPass
>>
(http://llvm.org/docs/**WritingAnLLVMPass.html#**LoopPass<http://llvm.org/docs/WritingAnLLVMPass.html#LoopPass>)
>> is misleading or
>> incorrect (or if I'm just missing something.) The documentation
states:
>>
>> "The doFinalization method ... is called when the pass framework
has
>> finished
>> calling runOnLoop <http://llvm.org/docs/**WritingAnLLVMPass.html#**
>> runOnLoop
<http://llvm.org/docs/WritingAnLLVMPass.html#runOnLoop>> for
>>
>> every loop in the program being compiled."
>>
>>  From this, I understood that for a single instance of a LoopPass
>> sub-class, the
>> doFinalization method would be called exactly once, after all loops had
>> been
>> seen. However in practice I am seeing doFinalization() being called
>> multiple
>> times per program. Digging into the code, it appears that LPPassManager
>> actually
>> makes the calls to doFinalization() at the end of it's
runOnFunction()
>> method
>>
(http://llvm.org/docs/doxygen/**html/LoopPass_8cpp_source.**html#l00281<http://llvm.org/docs/doxygen/html/LoopPass_8cpp_source.html#l00281>,
>> at time of
>> writing). This therefore means that doFinalization() can be called
>> multiple
>> times per LoopPass; as many as there are functions defined in the input
>> file.
>>
>
> my understanding is that this is the expected behaviour and the
> documentation
> should be improved (want to propose a patch?).
>
I'm actually really hoping to change this behavior in the not-too-distant
future.

The goal that I and several others have worked out is that for *all*
passes, the doInitialization and doFinalization are called once per module.
All of the doInitialization methods should be called before the first
pass's runOn***  method is called, and all of the doFinalization calls
should be after the last pass's runOn*** have finished.

The goal of the initialization and finalization methods is to allow
per-module caching, uniquing, setup, and teardown.

I know that we are quite far from this goal in practice sadly, but I think
the goal remains the same.

>
> Ciao, Duncan.
>
>
>> Assuming I have made no mistakes here, is this a case of poorly written
>> documentation, or an error in the implementation? I note that
>> FPPassManager does
>> it calls to FunctionPass' doFinalization() in it's own
doFinalization()
>> method,
>> which seems the correct behaviour to me.
>>
>> Thanks,
>> Stephen
>>
>>
>> ______________________________**_________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>
http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>>
>>
> ______________________________**_________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>
http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
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Duncan Sands

2012-Dec-17 12:57 UTC

head link

[LLVMdev] LoopPass doFinalization() called multiple times per program?

Hi Chandler,

On 17/12/12 13:47, Chandler Carruth wrote:> On Sun, Dec 16, 2012 at 7:23 AM, Duncan Sands <baldrick at free.fr
> <mailto:baldrick at free.fr>> wrote:
>
>     Hi Stephen,
>
>
>     On 13/12/12 18:58, Stephen McGruer wrote:
>
>         I'm wondering if the documentation for LoopPass
>         (http://llvm.org/docs/__WritingAnLLVMPass.html#__LoopPass
>         <http://llvm.org/docs/WritingAnLLVMPass.html#LoopPass>) is
misleading or
>         incorrect (or if I'm just missing something.) The documentation
states:
>
>         "The doFinalization method ... is called when the pass
framework has
>         finished
>         calling runOnLoop
>         <http://llvm.org/docs/__WritingAnLLVMPass.html#__runOnLoop
>         <http://llvm.org/docs/WritingAnLLVMPass.html#runOnLoop>>
for
>
>         every loop in the program being compiled."
>
>           From this, I understood that for a single instance of a LoopPass
>         sub-class, the
>         doFinalization method would be called exactly once, after all loops
had been
>         seen. However in practice I am seeing doFinalization() being called
multiple
>         times per program. Digging into the code, it appears that
LPPassManager
>         actually
>         makes the calls to doFinalization() at the end of it's
runOnFunction()
>         method
>        
(http://llvm.org/docs/doxygen/__html/LoopPass_8cpp_source.__html#l00281
>        
<http://llvm.org/docs/doxygen/html/LoopPass_8cpp_source.html#l00281>, at
>         time of
>         writing). This therefore means that doFinalization() can be called
multiple
>         times per LoopPass; as many as there are functions defined in the
input
>         file.
>
>
>     my understanding is that this is the expected behaviour and the
documentation
>     should be improved (want to propose a patch?).
>
>
> I'm actually really hoping to change this behavior in the
not-too-distant future.
>
> The goal that I and several others have worked out is that for *all*
passes, the
> doInitialization and doFinalization are called once per module. All of the
> doInitialization methods should be called before the first pass's
runOn***
>   method is called, and all of the doFinalization calls should be after the
last
> pass's runOn*** have finished.
would it still be possible to optimize and codegen functions as they are output
(rather than waiting for the module to be completely output before doing this)?

Ciao, Duncan.
>
> The goal of the initialization and finalization methods is to allow
per-module
> caching, uniquing, setup, and teardown.
>
> I know that we are quite far from this goal in practice sadly, but I think
the
> goal remains the same.
>
>
>     Ciao, Duncan.
>
>
>         Assuming I have made no mistakes here, is this a case of poorly
written
>         documentation, or an error in the implementation? I note that
>         FPPassManager does
>         it calls to FunctionPass' doFinalization() in it's own
doFinalization()
>         method,
>         which seems the correct behaviour to me.
>
>         Thanks,
>         Stephen
>
>
>         _________________________________________________
>         LLVM Developers mailing list
>         LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
http://llvm.cs.uiuc.edu
>         http://lists.cs.uiuc.edu/__mailman/listinfo/llvmdev
>         <http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>
>
>     _________________________________________________
>     LLVM Developers mailing list
>     LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
http://llvm.cs.uiuc.edu
>     http://lists.cs.uiuc.edu/__mailman/listinfo/llvmdev
>     <http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>
>

Chandler Carruth

2012-Dec-17 13:00 UTC

head link

[LLVMdev] LoopPass doFinalization() called multiple times per program?

On Mon, Dec 17, 2012 at 4:57 AM, Duncan Sands <baldrick at free.fr> wrote:
> would it still be possible to optimize and codegen functions as they are
> output
> (rather than waiting for the module to be completely output before doing
> this)?
>
I would assume so... What gives you pause here?

(TBH, I've not really thought about this deeply, so I may be missing
something obvious...)
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Stephen McGruer

2012-Dec-17 13:02 UTC

head link

[LLVMdev] LoopPass doFinalization() called multiple times per program?

I see. In the meantime, is there a suggested method to do actual
finalization code (i.e. code that runs after *all* of the loops have been
processed)?

Thanks,
Stephen


On 17 December 2012 12:57, Duncan Sands <baldrick at free.fr> wrote:
> Hi Chandler,
>
>
> On 17/12/12 13:47, Chandler Carruth wrote:
>
>> On Sun, Dec 16, 2012 at 7:23 AM, Duncan Sands <baldrick at free.fr
>> <mailto:baldrick at free.fr>> wrote:
>>
>>     Hi Stephen,
>>
>>
>>     On 13/12/12 18:58, Stephen McGruer wrote:
>>
>>         I'm wondering if the documentation for LoopPass
>>        
(http://llvm.org/docs/__**WritingAnLLVMPass.html#__**LoopPass<http://llvm.org/docs/__WritingAnLLVMPass.html#__LoopPass>
>>        
<http://llvm.org/docs/**WritingAnLLVMPass.html#**LoopPass<http://llvm.org/docs/WritingAnLLVMPass.html#LoopPass>>)
>> is misleading or
>>
>>         incorrect (or if I'm just missing something.) The
documentation
>> states:
>>
>>         "The doFinalization method ... is called when the pass
framework
>> has
>>         finished
>>         calling runOnLoop
>>        
<http://llvm.org/docs/__**WritingAnLLVMPass.html#__**runOnLoop<http://llvm.org/docs/__WritingAnLLVMPass.html#__runOnLoop>
>>
>>        
<http://llvm.org/docs/**WritingAnLLVMPass.html#**runOnLoop<http://llvm.org/docs/WritingAnLLVMPass.html#runOnLoop>>>
>> for
>>
>>         every loop in the program being compiled."
>>
>>           From this, I understood that for a single instance of a
LoopPass
>>         sub-class, the
>>         doFinalization method would be called exactly once, after all
>> loops had been
>>         seen. However in practice I am seeing doFinalization() being
>> called multiple
>>         times per program. Digging into the code, it appears that
>> LPPassManager
>>         actually
>>         makes the calls to doFinalization() at the end of it's
>> runOnFunction()
>>         method
>>        
(http://llvm.org/docs/doxygen/**__html/LoopPass_8cpp_source.__**
>>
html#l00281<http://llvm.org/docs/doxygen/__html/LoopPass_8cpp_source.__html#l00281>
>>         <http://llvm.org/docs/doxygen/**html/LoopPass_8cpp_source.**
>>
html#l00281<http://llvm.org/docs/doxygen/html/LoopPass_8cpp_source.html#l00281>>,
>> at
>>
>>         time of
>>         writing). This therefore means that doFinalization() can be
>> called multiple
>>         times per LoopPass; as many as there are functions defined in
the
>> input
>>         file.
>>
>>
>>     my understanding is that this is the expected behaviour and the
>> documentation
>>     should be improved (want to propose a patch?).
>>
>>
>> I'm actually really hoping to change this behavior in the
not-too-distant
>> future.
>>
>> The goal that I and several others have worked out is that for *all*
>> passes, the
>> doInitialization and doFinalization are called once per module. All of
the
>> doInitialization methods should be called before the first pass's
runOn***
>>   method is called, and all of the doFinalization calls should be after
>> the last
>> pass's runOn*** have finished.
>>
>
> would it still be possible to optimize and codegen functions as they are
> output
> (rather than waiting for the module to be completely output before doing
> this)?
>
> Ciao, Duncan.
>
>
>> The goal of the initialization and finalization methods is to allow
>> per-module
>> caching, uniquing, setup, and teardown.
>>
>> I know that we are quite far from this goal in practice sadly, but I
>> think the
>> goal remains the same.
>>
>>
>>     Ciao, Duncan.
>>
>>
>>         Assuming I have made no mistakes here, is this a case of poorly
>> written
>>         documentation, or an error in the implementation? I note that
>>         FPPassManager does
>>         it calls to FunctionPass' doFinalization() in it's own
>> doFinalization()
>>         method,
>>         which seems the correct behaviour to me.
>>
>>         Thanks,
>>         Stephen
>>
>>
>>         ______________________________**___________________
>>         LLVM Developers mailing list
>>         LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
>> http://llvm.cs.uiuc.edu
>>        
http://lists.cs.uiuc.edu/__**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/__mailman/listinfo/llvmdev>
>>        
<http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>> >
>>
>>
>>     ______________________________**___________________
>>     LLVM Developers mailing list
>>     LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
>> http://llvm.cs.uiuc.edu
>>    
http://lists.cs.uiuc.edu/__**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/__mailman/listinfo/llvmdev>
>>    
<http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
>> >
>>
>>
>>
> ______________________________**_________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>
http://lists.cs.uiuc.edu/**mailman/listinfo/llvmdev<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>
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