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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Few things you have to be careful with:<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">1) Create args properly and make sure the actual and formal parameter types should be same.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> If not add a cast.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">2) Make sure the return types are same.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">3) Set the calling conventions if any.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">4) Replace use if any.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">5) Then replace the instruction.<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">CallSite CS(Call);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">SmallVector<Value *, 8> Args(CS.arg_begin(), CS.arg_end());<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">CallInst *NewCI = CallInst::Create(NewFunc, Args);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">NewCI->setCallingConv(NewFunc->getCallingConv());<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">if (!Call->use_empty())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> Call->replaceAllUsesWith(NewCI);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">ReplaceInstWithInst(Call, NewCI);<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">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Ashutosh<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>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Pierre Gagelin via llvm-dev<br>
<b>Sent:</b> Monday, June 20, 2016 4:47 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [llvm-dev] function call replacement<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" style="margin-bottom:12.0pt">Hi everyone,<o:p></o:p></p>
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<p class="MsoNormal">I am trying to replace the call of a certain function with a call to another function. It would for example replace the following:<br>
<br>
%call = tail call noalias i8* @func(i64 10)<o:p></o:p></p>
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<p class="MsoNormal">by<br>
%call = tail call noalias i8* @other_func(i64 10)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I managed to declare other_func correctly but I am having troubles to understand how I should proceed to do the replacement.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
I tried to use ReplaceInstWithInst function as follows:<br>
<br>
CallInst *call_to_other_func_inst = IRBuilder.CreateCall(ptr_to_other_func, args);<br>
ReplaceInstWithInst(call_to_func_inst, newI);<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">LLVM builds correctly but the instrumentation crashes at optimization time. I know this isn't the correct way to do it because IRBuilder generates IR and I just want to have an instance of a CallInst. But I
don't see how it is supposed to be done?<br>
<br>
There are methods to create CallInst in the Instruction.h file but those needs to give an inserting point. Shoud I insert the call to other_func before the one to func and just remove the call instruction to func?<o:p></o:p></p>
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<p class="MsoNormal">Thanks for your help,<o:p></o:p></p>
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<p class="MsoNormal">Pierre<o:p></o:p></p>
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