[clang] [llvm] [RISCV] Add support for getHostCPUFeatures using hwprobe (PR #94352)

[Pengcheng Wang via cfe-commits]

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@@ -86,8 +86,14 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   // and other features (ex. mirco architecture feature) from mcpu
   if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
     StringRef CPU = A->getValue();
-    if (CPU == "native")
+    if (CPU == "native") {
       CPU = llvm::sys::getHostCPUName();
+      llvm::StringMap<bool> HostFeatures;
+      if (llvm::sys::getHostCPUFeatures(HostFeatures))
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wangpc-pp wrote:

Open discussion here: `CPU` may fail and return `generic`. Should we failback to use `getHostCPUFeatures` if `getHostCPUName` fails? Or we should use `getHostCPUFeatures` all the time?

https://github.com/llvm/llvm-project/pull/94352