[llvm] [Attributor] Take the address space from addrspacecast directly (PR #108258)

[Matt Arsenault via llvm-commits]

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@@ -12583,16 +12583,37 @@ struct AAAddressSpaceImpl : public AAAddressSpace {
   }
 
   ChangeStatus updateImpl(Attributor &A) override {
+    assert(A.getInfoCache().getFlatAddressSpace().has_value());
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arsenm wrote:

This assert is redundant, the attempt to use it will fail anyway (plus I still think it's nicer to not use optional, and just let the invalid address space value naturally not do anything) 

https://github.com/llvm/llvm-project/pull/108258