llvm dev - Nov 2016 - [ORC] SimpleCompiler and module transformations

Hi devs, hi Lang,

I use ORC’s SimpleCompiler to compile modules into object files and it works
just great, however I’m having an issue:
a module gets changed a bit when I compile it (some
transformations/optimizations applied).
I tried to set optimization level of a TargetMachine to None, but the module
gets changed anyway.

The question is: how can I prevent a module from being modified during
compilation?
I can make a clone of a module, but I’m curious if there are other ways to
achieve the same goal.

More context:

When I run a program I try to get object file for a module from a cache.
If the object file exists, then I just proceed to a module analysis phase.
If the object does not exist, then I compile the module, put object file into a
cache, and then proceed to a module analysis phase.
In other words:

  let object = cache.getObject(module);
  if object == null {
    object = compile(module)
    cache.putObject(object, module)
  }
  processModule(module)

When I run my program two times, then I basically analyze two different modules,
even though they are loaded from the same bitcode file.

Please, let me know if more information/clarification is needed.

Any hints, suggestions, and recommendations are more than welcome :)

-- 
AlexDenisov
Software Engineer, http://lowlevelbits.org

Naively, I suspect you'd have to clone it - there are some optimizations
that must be done for correctness on the IR (such as the always inlining
pass that inlines any functions that specify they /must/ be inlined).

On Wed, Nov 9, 2016 at 1:32 AM Alex Denisov via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi devs, hi Lang,
>
> I use ORC’s SimpleCompiler to compile modules into object files and it
> works just great, however I’m having an issue:
> a module gets changed a bit when I compile it (some
> transformations/optimizations applied).
> I tried to set optimization level of a TargetMachine to None, but the
> module gets changed anyway.
>
> The question is: how can I prevent a module from being modified during
> compilation?
> I can make a clone of a module, but I’m curious if there are other ways to
> achieve the same goal.
>
> More context:
>
> When I run a program I try to get object file for a module from a cache.
> If the object file exists, then I just proceed to a module analysis phase.
> If the object does not exist, then I compile the module, put object file
> into a cache, and then proceed to a module analysis phase.
> In other words:
>
>   let object = cache.getObject(module);
>   if object == null {
>     object = compile(module)
>     cache.putObject(object, module)
>   }
>   processModule(module)
>
> When I run my program two times, then I basically analyze two different
> modules, even though they are loaded from the same bitcode file.
>
> Please, let me know if more information/clarification is needed.
>
> Any hints, suggestions, and recommendations are more than welcome :)
>
> --
> AlexDenisov
> Software Engineer, http://lowlevelbits.org
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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> On Nov 9, 2016, at 9:02 AM, David Blaikie via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Naively, I suspect you'd have to clone it - there are some
optimizations that must be done for correctness on the IR (such as the always
inlining pass that inlines any functions that specify they /must/ be inlined).
> 
That could be solved by "pre-optimizing”. 
However that wouldn’t be enough: there are IR transformations that are done as
part of the codegen (codegenprepare for instance).

Right now in LLVM there is no other safe way (that I know of) than cloning
before processing a module.


— 
Mehdi
> On Wed, Nov 9, 2016 at 1:32 AM Alex Denisov via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> Hi devs, hi Lang,
> 
> I use ORC’s SimpleCompiler to compile modules into object files and it
works just great, however I’m having an issue:
> a module gets changed a bit when I compile it (some
transformations/optimizations applied).
> I tried to set optimization level of a TargetMachine to None, but the
module gets changed anyway.
> 
> The question is: how can I prevent a module from being modified during
compilation?
> I can make a clone of a module, but I’m curious if there are other ways to
achieve the same goal.
> 
> More context:
> 
> When I run a program I try to get object file for a module from a cache.
> If the object file exists, then I just proceed to a module analysis phase.
> If the object does not exist, then I compile the module, put object file
into a cache, and then proceed to a module analysis phase.
> In other words:
> 
>   let object = cache.getObject(module);
>   if object == null {
>     object = compile(module)
>     cache.putObject(object, module)
>   }
>   processModule(module)
> 
> When I run my program two times, then I basically analyze two different
modules, even though they are loaded from the same bitcode file.
> 
> Please, let me know if more information/clarification is needed.
> 
> Any hints, suggestions, and recommendations are more than welcome :)
> 
> --
> AlexDenisov
> Software Engineer, http://lowlevelbits.org <http://lowlevelbits.org/>
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<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
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