[llvm] [LiveVariables] Mark use as implicit-def if def is a subregister (PR #119446)

[Shilei Tian via llvm-commits]

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@@ -277,10 +277,21 @@ void LiveVariables::HandlePhysRegUse(Register Reg, MachineInstr &MI) {
           continue;
         if (PartDefRegs.count(SubReg))
           continue;
+
+        // Check if SubReg is defined at LastPartialDef.
+        bool IsDefinedHere = false;
+        for (int i = 0; i < LastPartialDef->getNumOperands(); ++i) {
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shiltian wrote:

nit: I don't know the rules of simple induction variable, but I'd name it `int I`.

https://github.com/llvm/llvm-project/pull/119446