[clang] [PGO] Add a clang option -fprofile-continuous that enables PGO continuous mode (PR #124353)

[David Li via cfe-commits]

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@@ -3033,6 +3033,14 @@ indexed format, regardeless whether it is produced by frontend or the IR pass.
   overhead. ``prefer-atomic`` will be transformed to ``atomic`` when supported
   by the target, or ``single`` otherwise.
 
+.. option:: -fprofile-continuous
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david-xl wrote:

Better to add an example to show the usage.

https://github.com/llvm/llvm-project/pull/124353