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<p class="MsoNormal"><span lang="EN-US">Hi <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I am trying to fix a bug in MachineCSE and have one question about following code:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">*********************************************<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">// Go through implicit defs of CSMI and MI, if a def is not dead at MI,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">// we should make sure it is not dead at CSMI.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">if (MO.isImplicit() && !MO.isDead() && CSMI->getOperand(i).isDead())<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ImplicitDefsToUpdate.push_back(i);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">// Keep track of implicit defs of CSMI and MI, to clear possibly<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">// made-redundant kill flags.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">if (MO.isImplicit() && !MO.isDead() && OldReg == NewReg)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> ImplicitDefs.push_back(OldReg);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">if (OldReg == NewReg) {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> --NumDefs;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> continue;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">}<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">**********************************************<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">From Above source code, it seems that CSE does not handle instruction which
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">have one operand that is ‘implicit+isDead+isDef’.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Base on my understanding, implicit dead register is mean clobbered, so it is not safe to<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">do CSE. Is this right?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Best wishes<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Michael<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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