[clang] [Sema] Fast-path simple plain auto deduction in DeduceAutoType (PR #188196)

[via cfe-commits]

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@@ -183,6 +183,11 @@ Non-comprehensive list of changes in this release
 
 - Added header ``endian.h`` which contains byte order helpers specified in POSIX
 
+- Improved the performance of ``auto`` deduction by adding the fast path
+  for additional simple cases, including non-canonical initializer types,
+  top-level-cv-qualified ``auto``, and single-level ``auto*`` declarators in
+  supported language modes.
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Sirraide wrote:

```suggestion
- Improved the performance of ``auto`` deduction by adding a fast path
  for simple cases, including ``auto``, ``const auto``, and ``auto*``. (#GH186274)
```
This is a bit simpler I think

https://github.com/llvm/llvm-project/pull/188196