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

[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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vporpo wrote:

Declaring the `RegionPass` class in `Region.h` is a bit strange. Wouldn't it make more sense to move `Pass.*` to the vectorizer too?

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