[clang] [llvm] [PowerPC][X86] Make cpu id builtins target independent and lower for PPC (PR #68919)

[Eli Friedman via llvm-commits]

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@@ -359,6 +359,13 @@ class LLVM_LIBRARY_VISIBILITY PPCTargetInfo : public TargetInfo {
   bool isSPRegName(StringRef RegName) const override {
     return RegName.equals("r1") || RegName.equals("x1");
   }
+
+  // We support __builtin_cpu_supports/__builtin_cpu_is on targets that
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efriedma-quic wrote:

Musl targets are supposed to use a "musl" triple.  We already have Triple::isMusl(). If it's somehow possible for both isOSGlibc() and isMusl() to be true, I'd consider that a bug in isOSGlibc().

https://github.com/llvm/llvm-project/pull/68919