[llvm] [InlineSpiller] Do not fold undef copies (PR #147392)

[Jeffrey Byrnes via llvm-commits]

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@@ -946,6 +946,9 @@ foldMemoryOperand(ArrayRef<std::pair<MachineInstr *, unsigned>> Ops,
     if (MO.isUse() && !MO.readsReg() && !MO.isTied())
       continue;
 
+    if (MI->isCopy() && MI->getOperand(1).isUndef())
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jrbyrnes wrote:

> Oh, I now see in the other PR, this is from hacking up the failed ranges. 

Yeah -- the test case is probably misleading, since it's using the MIR mid RA (i.e. after cleanedFailedVReg has created its version of the liveness)

https://github.com/llvm/llvm-project/pull/147392