[llvm] [DirectX] Make dx.RawBuffer an op that can't be replaced (PR #154620)

[Farzon Lotfi via llvm-commits]

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@@ -847,6 +847,8 @@ class TargetExtType : public Type {
     CanBeLocal = 1U << 2,
     // This type may be used as an element in a vector.
     CanBeVectorElement = 1U << 3,
+    // This type can not be replaced in an optimization pass.
+    NoReplacement = 1U << 4,
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farzonl wrote:

> * Docs should use `///`

None of the other comments were doing this,  will update all of them.

https://github.com/llvm/llvm-project/pull/154620