[clang] [llvm] [BPF] introduce `__attribute__((bpf_fastcall))` (PR #101228)

[Aaron Ballman via cfe-commits]

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@@ -2189,6 +2189,14 @@ def BTFTypeTag : TypeAttr {
   let LangOpts = [COnly];
 }
 
+def BPFFastCall : InheritableAttr,
+                  TargetSpecificAttr<TargetBPF> {
+  let Spellings = [GCC<"bpf_fastcall">];
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AaronBallman wrote:

Does GCC support this attribute with this spelling? If not, this should use the `Clang` spelling instead of the `GCC` spelling.

https://github.com/llvm/llvm-project/pull/101228