llvm dev - Jul 2017 - Is there any pass existing in llvm which does machine copy propogation ?

Hi All,

I was looking into MachineCopyPropagationPass.ccp file in llvm, which in first
look, looks likes to me doing only redundant copy elimination in same basic
block.

I am interested in any pass which is doing copy propogation across the basic
block in a function.

Let me know if any such pass exist ?

Thanks,
Deepali
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Hexagon has RDFCopy.cpp that does that.  It uses RDF framework that is 
currently under lib/Target/Hexagon, but is meant to be 
target-independent.  See https://reviews.llvm.org/D29295.

What target are you interested in?

-Krzysztof


On 7/21/2017 2:18 AM, Rai, Deepali via llvm-dev wrote:
> Hi All,
> 
> I was looking into MachineCopyPropagationPass.ccp file in llvm, which in 
> first look, looks likes to me doing only redundant copy elimination in 
> same basic block.
> 
> I am interested in any pass which is doing copy propogation across the 
> basic block in a function.
> 
> Let me know if any such pass exist ?
> 
> Thanks,
> 
> Deepali
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation

FWIW, there is also this proposed change

https://reviews.llvm.org/D30751 [MachineCopyPropagation] Extend pass to 
do COPY source forwarding

which enhances the MachineCopyPropagation pass to forward copied 
registers, though it still only operates at the block level.

It might be possible to extend this pass to work non-locally to some 
degree, but that should probably be evaluated against replacing it with 
RDFCopy once that pass is confirmed to work for all targets.

On 7/21/2017 10:25 AM, Krzysztof Parzyszek via llvm-dev
wrote:
> Hexagon has RDFCopy.cpp that does that.  It uses RDF framework that is 
> currently under lib/Target/Hexagon, but is meant to be 
> target-independent.  See https://reviews.llvm.org/D29295.
> 
> What target are you interested in?
> 
> -Krzysztof
> 
> 
> On 7/21/2017 2:18 AM, Rai, Deepali via llvm-dev wrote:
>> Hi All,
>>
>> I was looking into MachineCopyPropagationPass.ccp file in llvm, which 
>> in first look, looks likes to me doing only redundant copy elimination 
>> in same basic block.
>>
>> I am interested in any pass which is doing copy propogation across the 
>> basic block in a function.
>>
>> Let me know if any such pass exist ?
>>
>> Thanks,
>>
>> Deepali
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> 
-- 
Geoff Berry
Employee of Qualcomm Datacenter Technologies, Inc.
  Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm 
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the Code 
Aurora Forum, a Linux Foundation Collaborative Project.

Thanks Krzysztof for the quick response.
I looking for x86 target.

Thanks,
-Deepali
-----Original Message-----
From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
Krzysztof Parzyszek via llvm-dev
Sent: Friday, July 21, 2017 7:55 PM
To: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] Is there any pass existing in llvm which does machine
copy propogation ?

Hexagon has RDFCopy.cpp that does that.  It uses RDF framework that is currently
under lib/Target/Hexagon, but is meant to be target-independent.  See
https://reviews.llvm.org/D29295.

What target are you interested in?

-Krzysztof


On 7/21/2017 2:18 AM, Rai, Deepali via llvm-dev wrote:
> Hi All,
> 
> I was looking into MachineCopyPropagationPass.ccp file in llvm, which 
> in first look, looks likes to me doing only redundant copy elimination 
> in same basic block.
> 
> I am interested in any pass which is doing copy propogation across the 
> basic block in a function.
> 
> Let me know if any such pass exist ?
> 
> Thanks,
> 
> Deepali
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The
Linux Foundation _______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

At the moment X86 does not have a register unit for the upper part of 
EAX (not covered by AX), which makes AX and EAX have the same set of 
register units. This leads to incorrect results with RDF because writing 
to AX preserves the upper part of EAX, and this currently cannot be 
represented. This is somewhat of a known limitation.

Adding cc:Quentin: maybe he'll say what he thinks about adding that unit.

-Krzysztof

On 7/24/2017 12:32 AM, Rai, Deepali via llvm-dev wrote:
> Thanks Krzysztof for the quick response.
> I looking for x86 target.
> 
> Thanks,
> -Deepali
> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of
Krzysztof Parzyszek via llvm-dev
> Sent: Friday, July 21, 2017 7:55 PM
> To: llvm-dev at lists.llvm.org
> Subject: Re: [llvm-dev] Is there any pass existing in llvm which does
machine copy propogation ?
> 
> Hexagon has RDFCopy.cpp that does that.  It uses RDF framework that is
currently under lib/Target/Hexagon, but is meant to be target-independent.  See
https://reviews.llvm.org/D29295.
> 
> What target are you interested in?
> 
> -Krzysztof
> 
> 
> On 7/21/2017 2:18 AM, Rai, Deepali via llvm-dev wrote:
>> Hi All,
>>
>> I was looking into MachineCopyPropagationPass.ccp file in llvm, which
>> in first look, looks likes to me doing only redundant copy elimination
>> in same basic block.
>>
>> I am interested in any pass which is doing copy propogation across the
>> basic block in a function.
>>
>> Let me know if any such pass exist ?
>>
>> Thanks,
>>
>> Deepali
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> 
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
by The Linux Foundation _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation