[clang] [Clang] Constant Expressions inside of GCC' asm strings (PR #131003)

[Erich Keane via cfe-commits]

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@@ -1958,6 +1958,24 @@ references can be used instead of numeric references.
       return -1;
   }
 
+
+Constexpr strings in GNU ASM statememts
+=======================================
+
+In C++11 mode (and greater), Clang supports specifying the template,
+constraints, and clobber strings with a parenthesized constant expression
+producing an object with ``data`` and ``size`` member functions,
+such as ``std::string``.
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erichkeane wrote:

to be coy, it might be nice to list `std::string_view` and `std::vector` here too (or just `std::vector<char>`?).  There are ALSO constraints based on whether `data` returns a char type or `size` returns an integral type, right? We should probably mention that.

https://github.com/llvm/llvm-project/pull/131003