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<p class="MsoNormal">Hi Raghesh,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Partial inline has support for function unswitching, you can explore it.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Note: It does not handle the functions marked with no-inline attribute.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Ashutosh<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>raghesh via llvm-dev<br>
<b>Sent:</b> Friday, June 7, 2019 2:03 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [llvm-dev] Use case for function unswitching.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[CAUTION: External Email] <o:p></o:p></p>
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<p class="MsoNormal">Dear All, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It would be great if anyone help me out in finding a use case similar to the following example.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">__attribute__((noinline))<br>
int f (int p) {<br>
if (p == 10) { // if-1<br>
return 0;<br>
}<o:p></o:p></p>
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<p class="MsoNormal"> // Some statements here.<br>
return 2;<br>
}<br>
<br>
int g(int p) {<br>
return f(p);<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">Here, I would like to see if the compiler does a transformation, where the if statement (if-1) in the body of the function 'f' is removed from 'f' and pushed to the caller 'g' as follows. Please note that I have forced not to inline 'f'.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">int f (int p) {<o:p></o:p></p>
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<p class="MsoNormal"> // Some statements here.<br>
return 2;<br>
}<br>
<br>
int g(int p) {<o:p></o:p></p>
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<p class="MsoNormal"> if (p == 10) { // if-1<br>
return 0;<br>
}<br>
return f(p);<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">This is a simple example that I used just to demonstrate the optimization (we may call it as function switching). If you know about any other use cases, where similar transformation happens, please let me know. When I generated the llvm
IR (with -O3) such a transformation was not observed.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Raghesh Aloor<o:p></o:p></p>
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<p class="MsoNormal">PhD Scholar<o:p></o:p></p>
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<p class="MsoNormal">PACE Lab, Dept. of CSE, IIT Madras<br>
<a href="http://www.cse.iitm.ac.in/~raghesh/" target="_blank">http://www.cse.iitm.ac.in/~raghesh/</a><o:p></o:p></p>
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