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Hi Filip <br>
Thank you for your detailed explanation, I was actually
looking to implement an adaptive approach which is basically when
some function executed more frequently, I was trying to drop that
function and compiled and linked with new optimized function. I
just did the following - <br>
whenever some function executed more times , I
called-back to program, so I that I could be able to call
freeMachineCodeForFunction (F) then I compiled that more frequent
function with some kind of optimization. But , still I am getting
previous function signature and not newest one. Could you please
explain , why we can not use this freeMachineCodeForFunction for
this purpose. If not, how we can hook some instruction in emitted
machine code that will call back to our code in llvm. <br>
<br>
Thanks<br>
<br>
With regards <br>
Sri.<br>
<div class="moz-cite-prefix">On 04/26/2014 05:39 AM, Filip Pizlo
wrote:<br>
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<div>This isn't currently supported directly. It depends on what
you're doing, which JIT you're using, how you use modules, and
to what extent you're relying on LLVM to do linking for you. </div>
<div><br>
</div>
<div>You can't safely drop a function's code if you have other
functions in that module. </div>
<div><br>
</div>
<div>You can't safely drop a module if there are other modules
that have calls that you've already resolved to functions in the
module you're dropping unless you have your own mechanism for
unlinking those calls. </div>
<div><br>
</div>
<div>The MCJIT currently does support dropping the memory for a
module, but it involves destroying the MCJIT execution engine
object. This works best if you use your own JIT memory manager
and you steal the executable memory from the MCJIT, and delete
the MCJIT after code is generated. Then your own memory manager
can manage the memory however you like. This depends on not
having LLVM call instructions resolve to any of the functions
you would be dropping. WebKit is an example of a system that
does this. Each function gets it's own module and all LLVM data
structures are dropped once the code is compiled. Call
instructions are only used for intrinsics and for runtime calls;
source level calls are implemented as patchpoints and WebKit
does all of the linking (and unlinking). </div>
<div><br>
</div>
<div>Long story short, there is no shrink-wrapped solution but
it's doable if you're willing to get dirty. <br>
<br>
-Fil</div>
<div><br>
On Apr 25, 2014, at 3:44 PM, Sri <<a moz-do-not-send="true"
href="mailto:emdcdeveloper@gmail.com">emdcdeveloper@gmail.com</a>>
wrote:<br>
<br>
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Hi<br>
Currently , I have doing some experimental work by
using llvm, Is it possible to drop the machine code once it
has been generated for particular function while program
executing. For example some <b>void test(int)</b> function
has been executed on native machine , I want to drop the code
before I start execute some other function in my long running
program.<br>
<br>
Thanks.<br>
<br>
With regards <br>
Sri. <br>
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