[clang] [clang] Optimize Lexer hot path to reduce compile time (PR #177153)

[Corentin Jabot via cfe-commits]

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@@ -283,6 +285,11 @@ class Token {
   ///
   bool isAtStartOfLine() const { return getFlag(StartOfLine); }
 
+  /// isAtPhysicalStartOfLine - Return true if this token is at the start of a
+  /// physical line.
+  ///
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cor3ntin wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/177153