[llvm] [CodeGen] Mark LIFETIME_START and LIFETIME_END as not safe to move (PR #211179)

[Matt Arsenault via llvm-commits]

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@@ -1403,11 +1403,6 @@ bool MachineInstr::wouldBeTriviallyDead() const {
   if (isFakeUse())
     return false;
 
-  // LIFETIME markers should be preserved.
-  // FIXME: Why are LIFETIME markers not considered in MachineInstr::isPosition?
-  if (isLifetimeMarker())
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arsenm wrote:

There's another of these in isDead 

https://github.com/llvm/llvm-project/pull/211179