[llvm] [IR] Allow poison argument to lifetime markers (PR #151148)

[Matt Arsenault via llvm-commits]

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@@ -26656,14 +26656,17 @@ Arguments:
 The first argument is a constant integer, which is ignored and will be removed
 in the future.
 
-The second argument is a pointer to an ``alloca`` instruction.
+The second argument is either a pointer to an ``alloca`` instruction or
+a ``poison`` value.
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arsenm wrote:

Can we relax this to any constant? As it is this will require special casing in llvm-reduce at a minimum 

https://github.com/llvm/llvm-project/pull/151148