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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black">Sure could, although that IR would have to be instanced/recompiled for every call to foo to avoid issues when foo is called from multiple threads (as otherwise
the globals could be overwritten). <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black"> Lang Hames [lhames@gmail.com]<br>
<b>Sent:</b> Friday, September 18, 2015 8:32 PM<br>
<b>To:</b> Mueller-Roemer, Johannes Sebastian<br>
<b>Cc:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> Re: [llvm-dev] ExecutionEngine::runFunction and libffi</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Hi Johannes, <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">No, runFunction isn't particularly useable at the moment. So far we've been encouraging people to use getSymbolAddress and call functions directly, handling argument and return marshaling themselves.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Given that runFunction is calling in to LLVM generated code, I think it makes sense to add some utilities to the execution engine library (rather than rely on libffi) to make marshaling/un-marshaling easier. Given
a function prototype T1 foo(T2, T3, ...), a utility could create new IR along these lines:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">declare T1 foo(T2, T3, ...);</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">T1 r;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">T2 arg1;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">T3 arg2;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">...</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">void foo_helper() {</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black"> x1 = load arg1;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black"> x2 = load arg2;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black"> ...</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black"> x0 = call foo(x1, x2, ...);</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black"> store x0, r;</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Courier New";color:black">}</span><span style="color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">For primitive types all that would be needed is to copy the values into the globals, invoke the helper, then read the return value back out.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Would something like this satisfy your use case?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Cheers,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Lang.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">On Fri, Sep 18, 2015 at 6:46 AM, Mueller-Roemer, Johannes Sebastian via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="color:black">I noticed that runFunction (for MCJIT) is very limited. At the same time the interpreter already has a fairly generic way of calling functions
from a pointer and a Function * (for description) using libffi. Would it make sense to pull that functionality out into a small support library and using it in MCJIT? As is runFunction isn’t particularly usable.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US" style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">--<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">Johannes S. Mueller-Roemer, MSc<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">Wiss. Mitarbeiter - Interactive Engineering Technologies (IET)<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">Fraunhofer-Institut für Graphische Datenverarbeitung IGD<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">Fraunhoferstr. 5 | 64283 Darmstadt | Germany<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black">Tel
<a href="tel:%2B49%206151%20155-606" target="_blank">+49 6151 155-606</a> | Fax
<a href="tel:%2B49%206151%20155-139" target="_blank">+49 6151 155-139</a><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black"><a href="mailto:johannes.mueller-roemer@igd.fraunhofer.de" target="_blank">johannes.mueller-roemer@igd.fraunhofer.de</a> |
<a href="http://www.igd.fraunhofer.de" target="_blank">www.igd.fraunhofer.de</a><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:black"> <o:p></o:p></span></p>
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