[clang] [llvm] [WIP][RISCV] Support __builtin_cpu_init and __builtin_cpu_supports (PR #99700)

[Piyou Chen via cfe-commits]

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@@ -1020,3 +1020,64 @@ std::string RISCVISAInfo::getTargetFeatureForExtension(StringRef Ext) {
   return isExperimentalExtension(Name) ? "experimental-" + Name.str()
                                        : Name.str();
 }
+
+struct RISCVExtBit {
+  const StringRef ext;
+  uint64_t bitpos;
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BeMg wrote:

Does it need `uint64_t` for bit position? I think the value doesn't exceed 63.

https://github.com/llvm/llvm-project/pull/99700