[clang] [llvm] [clang] Add cc1 --output-asm-variant= to set output syntax (PR #109360)

[Fangrui Song via cfe-commits]

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@@ -7209,6 +7209,9 @@ def fuse_ctor_homing: Flag<["-"], "fuse-ctor-homing">,
 def as_secure_log_file : Separate<["-"], "as-secure-log-file">,
   HelpText<"Emit .secure_log_unique directives to this filename.">,
   MarshallingInfoString<CodeGenOpts<"AsSecureLogFile">>;
+def output_asm_variant : Joined<["--"], "output-asm-variant=">,
+  HelpText<"Select the asm variant (integer) to use for output">,
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MaskRay wrote:

Appreciate the comments. 

Yes, the AssemblerDIalect choices could be useful for other targets. SystemZ has `AssemblerDIalect`s that I am not familiar with. AArch64 seems to have one as well. 

https://github.com/llvm/llvm-project/pull/109360