[clang] Mechanically port bulk of x86 builtins to TableGen (PR #120831)

[Chandler Carruth via cfe-commits]

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@@ -108,9 +109,15 @@ class PrototypeParser {
     } else if (T.consume_back("&")) {
       ParseType(T);
       Type += "&";
+    } else if (T.consume_front("long long")) {
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chandlerc wrote:

This does maybe point at something that doesn't add much complexity -- I can condition using `O` on a flag that only X86 builtins use so it doesn't impact any other targets? That should be quite simple, and then other targets can opt in if/when they wish?

https://github.com/llvm/llvm-project/pull/120831