[clang] [llvm] RFC: Implementing new mechanism for hard register operands to inline asm as a constraint. (PR #85846)

[Eli Friedman via llvm-commits]

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@@ -2250,6 +2250,48 @@ Query for this feature with ``__has_extension(gnu_asm_constexpr_strings)``.
       asm((std::string_view("nop")) ::: (std::string_view("memory")));
    }
 
+Hard Register Operands for ASM Constraints
+==========================================
+
+Clang supports the ability to specify specific hardware registers in inline
+assembly constraints via the use of curly braces ``{}``.
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efriedma-quic wrote:

Maybe should explicitly say that the register names are the same names used in the clobber list.

https://github.com/llvm/llvm-project/pull/85846