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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Do you have a use of the new variable as well? If not, it might be optimized out between the point where you create it and your MachineFunction pass.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></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""> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>n3v3rm03 via llvm-dev<br>
<b>Sent:</b> Friday, January 18, 2019 5:57 AM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [llvm-dev] Can't find symbol from llvm backend<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">Hi, I am new to llvm. <o:p></o:p></p>
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<p class="MsoNormal">I create a global variable called "test_llvm_var" in the front end function pass like this:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> new GlobalVariable(*m, tmp->getType(), true, llvm::GlobalValue::ExternalLinkage, tmp, "test_llvm_var");<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">where tmp is a function.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Then I tried to access this global variable in the back end MachineFunctionPass like this:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> MCContext& MCC = MF.getContext();<br>
MCSymbol* MCS = MCC.lookupSymbol("test_llvm_var");<br>
if (MCS == NULL) {<br>
errs() << ">>> MCSymbol is null\n";<br>
} <br>
else {<br>
MCS->dump();<br>
} <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> (MF is a MachineFunction).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">However I always get MCS==NULL, there is no symbol called test_llvm_var in the backend.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Am I doing something wrong? What I would like to do is to modify the global variable's value from the backend pass.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Any help would be appreciated.<o:p></o:p></p>
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<p class="MsoNormal">Thank you!<o:p></o:p></p>
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