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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">There’s probably a lot that we could do, but I can’t think of anything easy.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Basically every time we need to look up a symbol by name we’re going to each module and saying “Do you have this symbol?” It would likely be much better if
we grabbed the function names from the module and did the search ourselves so that we could keep some information about the things that didn’t match and optimize the next search.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Andy<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Jim Grosbach [mailto:grosbach@apple.com]
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<b>Sent:</b> Monday, October 21, 2013 4:39 PM<br>
<b>To:</b> Kaylor, Andrew; Yaron Keren<br>
<b>Cc:</b> <llvmdev@cs.uiuc.edu><br>
<b>Subject:</b> Re: [LLVMdev] An enhancement for MCJIT::getFunctionAddress<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The search is linear? If that’s really true, we should fix that.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Oct 21, 2013, at 10:14 AM, Kaylor, Andrew <<a href="mailto:andrew.kaylor@intel.com">andrew.kaylor@intel.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I should have read this before sending my previous reply. :-)</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’m not a big fan of default parameters, but some form of what you are suggesting may be useful. See my other comments on this topic in the other reply.</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Andy</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span class="apple-converted-space"><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> </span></span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">Yaron
Keren [<a href="mailto:yaron.keren@gmail.com">mailto:yaron.keren@gmail.com</a>]<span class="apple-converted-space"> </span><br>
<b>Sent:</b><span class="apple-converted-space"> </span>Saturday, October 19, 2013 3:17 PM<br>
<b>To:</b><span class="apple-converted-space"> </span>Kaylor, Andrew; <<a href="mailto:llvmdev@cs.uiuc.edu">llvmdev@cs.uiuc.edu</a>><br>
<b>Subject:</b><span class="apple-converted-space"> </span>An enhancement for MCJIT::getFunctionAddress</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">In MCJIT, the old JIT functions are deprecated in favor of getFunctionAddress. <o:p></o:p></p>
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<p class="MsoNormal">Code like:<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> llvm::Function *F = M->getFunction(FuncName);</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> void *FN = EE->getPointerToFunction(F);</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">should be rewritten as<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> uint64_t FN = EE->getFunctionAddress(FuncName);</span><o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">While functionally identical, in case the correct module is known the new version will be much slower, linear with the number of added (but not loaded) modules, since it has to (possibly) search for the correct module while old code directly
searches the correct module.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">To solve the issue, getFunctionAddress could get an optional Module "hint" (=NULL by default) which - if provided - will make getSymbolAddress skip calling findModuleForSymbol (a very slow operation) and instead directly use the Module
provided.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Yaron<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:LLVMdev@cs.uiuc.edu">LLVMdev@cs.uiuc.edu</a> <a href="http://llvm.cs.uiuc.edu">http://llvm.cs.uiuc.edu</a><br>
<a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a><o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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