[llvm] [SandboxIR][SandboxVectorizer][NFC] Move Region to SandboxVectorizer. (PR #117237)

[Jorge Gorbe Moya via llvm-commits]

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@@ -107,6 +109,25 @@ class Region {
 #endif
 };
 
+/// A pass that runs on a Region.
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slackito wrote:

Including things like `FunctionPass` that operate on non-vectorizer-specific SandboxIR concepts like Function? I guess the question is whether we believe SandboxVectorizer is the only user that will create SandboxIR sub-pass pipelines or they can be useful elsewhere.

https://github.com/llvm/llvm-project/pull/117237