[clang] [clang] Introduce '-fint64-is-long-long' (PR #234780)

[Hubert Tong via cfe-commits]

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@@ -562,6 +562,9 @@ void TargetInfo::adjust(DiagnosticsEngine &Diags, LangOptions &Opts,
     }
   }
 
+  if (Opts.Int64LongLong)
+    Int64Type = SignedLongLong;
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hubert-reinterpretcast wrote:

I guess we don't have any targets where `long long` is wider than 64 bits, but I wonder if we should have some check here that the width is correct.

https://github.com/llvm/llvm-project/pull/234780