[clang] [llvm] [PowerPC] frontend get target feature from backend with cpu name (PR #137670)

[Amy Kwan via llvm-commits]

================
@@ -117,5 +121,27 @@ StringRef getNormalizedPPCTuneCPU(const Triple &T, StringRef CPUName) {
   return getNormalizedPPCTargetCPU(T, CPUName);
 }
 
+std::optional<StringMap<bool>> getPPCDefaultTargetFeatures(const Triple &T,
+                                                           StringRef CPU) {
+  std::optional<StringMap<bool>> FeaturesOpt =
+      getCPUDefaultTargetFeatures(CPU, BasicPPCSubTypeKV, BasicPPCFeatureKV);
+
+  if (!FeaturesOpt.has_value())
+    return std::nullopt;
+
+  StringMap<bool> Features = FeaturesOpt.value();
+  // FIXME: We need to check for the processor model 8548, since the backend
+  // does not support this processor. When this processor model is implemented
+  // within the backend, the following code can be removed.
+  if (CPU == "8548")
+    Features["spe"] = true;
+
+  // The target feature `quadword-atomics` is enabled by llvm back-end for
+  // power8 or power8 up, we disable the target feature if the triple is
+  // 32-bit.
----------------
amy-kwan wrote:

Is this comment more accurate? And just checking, but this will be enabled on for P8+ based on `getCPUDefaultTargetFeatures()`, right?
```suggestion
  // The target feature `quadword-atomics` is only supported for 64-bit
  // POWER8 and above.
```

https://github.com/llvm/llvm-project/pull/137670