llvm dev - Mar 2017 - [GSoC 2017] Project proposal queries

Hi,

My name is Radhika Ghosal and I'd like to participate in this year's
GSoC
in LLVM. I have been using LLVM for a research project for some time now,
and would love to contribute to it!

Below are the projects I'm interested in and a few questions; please
correct me if I am understanding something incorrectly:

- Code Compaction: [1]
Is it necessary to implement code compaction solely using interprocedural
link-time analyses, or this project may include compile-time optimizations
for size as well? (as in the style of the `-Os` flag in gcc)

I ask because solely using LTO for doing so may restrict us to using the
Gold linker or lld, both of which are still at development stage for
embedded targets like ARM (for lld) and AVR (not included in Gold, may have
lld support in the future), while compile-time optimizations for size may
yield more immediate results.

- Encode Analysis Results in MachineInstr IR: [2]
Does the analysis information have to be encoded within metadata in the
LLVM IR instructions (since the BasicBlock corresponding to the
MachineBasicBlock is always available), or something else must be done? I
am somewhat unsure of what is required, and would like to know more about
the project.

Thank you for your time!

Sincerely,
Radhika

[1]: http://llvm.org/OpenProjects.html#compaction
[2]: http://llvm.org/OpenProjects.html#encodeanalysis
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170315/ab114390/attachment.html>

> On Mar 15, 2017, at 10:10 AM, Radhika via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> My name is Radhika Ghosal and I'd like to participate in this
year's GSoC in LLVM. I have been using LLVM for a research project for some
time now, and would love to contribute to it!
> 
> Below are the projects I'm interested in and a few questions; please
correct me if I am understanding something incorrectly:
> 
> - Code Compaction: [1]
> Is it necessary to implement code compaction solely using interprocedural
link-time analyses, or this project may include compile-time optimizations for
size as well? (as in the style of the `-Os` flag in gcc)
> 
> I ask because solely using LTO for doing so may restrict us to using the
Gold linker or lld, both of which are still at development stage for embedded
targets like ARM (for lld) and AVR (not included in Gold, may have lld support
in the future), while compile-time optimizations for size may yield more
immediate results.
It is rare to have link-time specific optimizations in LLVM, usually LTO is just
a way to expose a larger body of code to the optimizer and thus getting better
results.
The link to the article on the open-project page seems dead so I don’t know
exactly what it was about. It seems also that this is quite an old “open
project” so it is not clear if it is still of high interest. For instance these
days Jessica is working on an outliner ( http://llvm.org/devmtg/2016-11/#talk21
<http://llvm.org/devmtg/2016-11/#talk21> ) to improve code-size
aggressively, I don’t know if there are other aspect people are interested to
look into.


> 
> - Encode Analysis Results in MachineInstr IR: [2]
> Does the analysis information have to be encoded within metadata in the
LLVM IR instructions (since the BasicBlock corresponding to the
MachineBasicBlock is always available), or something else must be done? I am
somewhat unsure of what is required, and would like to know more about the
project.
I don’t know about this one, but hopefully someone else will chime in (CC
Matthias randomly ;)).

— 
Mehdi

-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170315/b3e7cc6b/attachment-0001.html>

> On Mar 15, 2017, at 11:42 AM, Mehdi Amini via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
>> 
>> On Mar 15, 2017, at 10:10 AM, Radhika via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> 
>> Hi,
>> 
>> My name is Radhika Ghosal and I'd like to participate in this
year's GSoC in LLVM. I have been using LLVM for a research project for some
time now, and would love to contribute to it!
>> 
>> Below are the projects I'm interested in and a few questions;
please correct me if I am understanding something incorrectly:
>> 
>> - Code Compaction: [1]
>> Is it necessary to implement code compaction solely using
interprocedural link-time analyses, or this project may include compile-time
optimizations for size as well? (as in the style of the `-Os` flag in gcc)
>> 
>> I ask because solely using LTO for doing so may restrict us to using
the Gold linker or lld, both of which are still at development stage for
embedded targets like ARM (for lld) and AVR (not included in Gold, may have lld
support in the future), while compile-time optimizations for size may yield more
immediate results.
> 
> It is rare to have link-time specific optimizations in LLVM, usually LTO is
just a way to expose a larger body of code to the optimizer and thus getting
better results.
> The link to the article on the open-project page seems dead so I don’t know
exactly what it was about. It seems also that this is quite an old “open
project” so it is not clear if it is still of high interest. For instance these
days Jessica is working on an outliner ( http://llvm.org/devmtg/2016-11/#talk21
<http://llvm.org/devmtg/2016-11/#talk21> ) to improve code-size
aggressively, I don’t know if there are other aspect people are interested to
look into.
> 
> 
> 
>> 
>> - Encode Analysis Results in MachineInstr IR: [2]
>> Does the analysis information have to be encoded within metadata in the
LLVM IR instructions (since the BasicBlock corresponding to the
MachineBasicBlock is always available), or something else must be done? I am
somewhat unsure of what is required, and would like to know more about the
project.
> 
> I don’t know about this one, but hopefully someone else will chime in (CC
Matthias randomly ;)).
I don't know either. We gotta find the author of that proposal.

- Matthias

-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20170315/abb48fc3/attachment.html>