[llvm] [AArch64] Fix stp kill when merging forward. (PR #152994)

[Ricardo Jesus via llvm-commits]

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@@ -1193,7 +1193,8 @@ AArch64LoadStoreOpt::mergePairedInsns(MachineBasicBlock::iterator I,
       //   USE kill %w1   ; need to clear kill flag when moving STRWui downwards
       //   STRW %w0
       Register Reg = getLdStRegOp(*I).getReg();
-      for (MachineInstr &MI : make_range(std::next(I), Paired))
+      for (MachineInstr &MI :
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rj-jesus wrote:

I think the kill flags of `I` should be preserved here as they are used to [track defined registers](https://github.com/llvm/llvm-project/blob/d2b3e86321eaf954451e0a49534fa654dd67421e/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp#L1385).

https://github.com/llvm/llvm-project/pull/152994