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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In the context of MachineCode custom inserter, I’m trying to enforce the mapping of virtual register to a physical one.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">According to the documentation <a href="https://llvm.org/docs/CodeGenerator.html#mapping-virtual-registers-to-physical-registers">
https://llvm.org/docs/CodeGenerator.html#mapping-virtual-registers-to-physical-registers</a><o:p></o:p></p>
<p class="MsoNormal">There are two ways: the direct one and the indirect ones. The indirect ones refer
<span style="font-size:10.0pt;font-family:Consolas;color:black;background:white">
VirtRegMap class that I’ve never found. So I tried the direct one…<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Mapping virtual registers to physical registers<o:p></o:p></p>
<p class="MsoNormal">^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">There are two ways to map virtual registers to physical registers (or to memory<o:p></o:p></p>
<p class="MsoNormal">slots). The first way, that we will call *direct mapping*, is based on the use<o:p></o:p></p>
<p class="MsoNormal">of methods of the classes ``TargetRegisterInfo``, and ``MachineOperand``. The<o:p></o:p></p>
<p class="MsoNormal">second way, that we will call *indirect mapping*, relies on the ``VirtRegMap``<o:p></o:p></p>
<p class="MsoNormal">class in order to insert loads and stores sending and getting values to and from<o:p></o:p></p>
<p class="MsoNormal">memory.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The direct mapping provides more flexibility to the developer of the register<o:p></o:p></p>
<p class="MsoNormal">allocator; however, it is more error prone, and demands more implementation<o:p></o:p></p>
<p class="MsoNormal">work. Basically, the programmer will have to specify where load and store<o:p></o:p></p>
<p class="MsoNormal">instructions should be inserted in the target function being compiled in order<o:p></o:p></p>
<p class="MsoNormal">to get and store values in memory. To assign a physical register to a virtual<o:p></o:p></p>
<p class="MsoNormal">register present in a given operand, use ``MachineOperand::setReg(p_reg)``. To<o:p></o:p></p>
<p class="MsoNormal">insert a store instruction, use ``TargetInstrInfo::storeRegToStackSlot(...)``,<o:p></o:p></p>
<p class="MsoNormal">and to insert a load instruction, use ``TargetInstrInfo::loadRegFromStackSlot``.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">…<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I tried the direct mapping as following:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace;color:black"> MachineOperand destination = MI->getOperand(0);</span><span style="font-size:10.0pt;font-family:Monospace"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace;color:black"> MachineOperand offset = MI->getOperand(1);</span><span style="font-size:10.0pt;font-family:Monospace"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace">
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace;color:black">
</span><b><span style="font-size:10.0pt;font-family:Monospace;color:#7F0055">unsigned</span></b><span style="font-size:10.0pt;font-family:Monospace;color:black"> destinationReg = destination.getReg();</span><span style="font-size:10.0pt;font-family:Monospace"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace;color:black"> int64_t FrameIndex = offset.getIndex();</span><span style="font-size:10.0pt;font-family:Monospace"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> destination.setReg(CLP::FA_ROFF0+FrameIndex);<o:p></o:p></p>
<p class="MsoNormal"> destination.setIsDef(true);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> TII->loadRegFromStackSlot(*MBB,<o:p></o:p></p>
<p class="MsoNormal"> MI, destinationReg, FrameIndex,<o:p></o:p></p>
<p class="MsoNormal"> &CLP::FPUaOffsetClassRegClass, TRI);<o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
</span><span style="font-size:10.0pt;font-family:Monospace;color:black">The code after customInserter seems valid but the compilation later hang-up in an infinite loop in procedure computeVirtRegs(); of pass LiveIntervals::runOnMachineFunction.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:Monospace;color:black">In other targets, I’ve seen an example with a setIsDef(true) for such physically mapped register. Is there something missing in my code (register
other setting,…) ? <o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><br>
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<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><img border="0" width="536" height="49" id="_x0000_i1025" src="http://www.spacebel.be/wp-content/uploads/2018/02/image-sign-sbp30y-1.jpg" alt="http://www.spacebel.be/wp-content/uploads/2018/02/image-sign-sbp30y-1.jpg"></span><span style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p></o:p></span></p>
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<p class="MsoNormal" align="center" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;text-align:center">
<b><span style="font-size:10.0pt">Dominique Torette</span></b><span style="font-size:10.0pt">
<br>
System Architect<br>
Rue des Chasseurs Ardennais - Liège Science Park - B-4031 Angleur <br>
Tel: +32 (0) 4 </span><span lang="FR-BE" style="font-size:10.0pt">361 81 11 - Fax: +32 (0) 4 361 81 20
<br>
</span><span style="font-size:10.0pt"><a href="http://www.spacebel.be/"><span lang="FR-BE" style="color:blue">www.spacebel.be</span></a></span><span lang="FR-BE" style="font-size:12.0pt;font-family:"Times New Roman","serif""><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="FR-BE"><o:p> </o:p></span></p>
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