[clang] [llvm] [X86] support reserve r8~r15 on X86_64 (PR #180242)

[Phoebe Wang via cfe-commits]

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@@ -7084,6 +7077,10 @@ def mapxf : Flag<["-"], "mapxf">, Group<m_x86_Features_Group>;
 def mno_apxf : Flag<["-"], "mno-apxf">, Group<m_x86_Features_Group>;
 def mapx_inline_asm_use_gpr32 : Flag<["-"], "mapx-inline-asm-use-gpr32">, Group<m_Group>,
                                 HelpText<"Enable use of GPR32 in inline assembly for APX">;
+foreach i = {8, 10-15} in
+    def ffixed_r#i : Flag<["-"], "ffixed-r"#i>, Group<m_Group>,
+    HelpText<"Reserve the r"#i#" register (x86_64 only)">;
+
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phoebewang wrote:

I'm not driver expert, but this seems too verbose to me. Is it better to use `-ffixed-register=8,9,10,...`?

https://github.com/llvm/llvm-project/pull/180242