[llvm] [CodeGen] Refactor DeadMIElim isDead and GISel isTriviallyDead (PR #105956)

[Nikita Popov via llvm-commits]

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@@ -1725,6 +1730,10 @@ class MachineInstr
   /// the instruction's location and its intended destination.
   bool isSafeToMove(bool &SawStore) const;
 
+  /// Return true if this instruction can be considered dead if all of its
+  /// defined registers are dead.
+  bool canBeDead() const;
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nikic wrote:

In IR the corresponding query is called wouldInstructionBeTriviallyDead(). I'd maybe use `wouldBeTriviallyDead()` here for symmetry.

https://github.com/llvm/llvm-project/pull/105956