[clang] [clang] Provide an SSE4.2 implementation of identifier token lexer (PR #68962)

[via cfe-commits]

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@@ -1847,19 +1851,46 @@ bool Lexer::LexUnicodeIdentifierStart(Token &Result, uint32_t C,
   return true;
 }
 
+static const char *fastParseASCIIIdentifier(const char *CurPtr, const char* BufferEnd) {
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cor3ntin wrote:

```suggestion
static const char *fastParseASCIIIdentifier(const char *CurPtr, [[maybe_unused]] const char* BufferEnd) {
```

This way you can get rid of the `#else`

https://github.com/llvm/llvm-project/pull/68962