[clang] [CIR] Emit target-cpu, target-features, and tune-cpu attrs on cir.func (PR #193458)

[Bruno Cardoso Lopes via cfe-commits]

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@@ -698,6 +699,78 @@ void CIRGenModule::setCommonAttributes(GlobalDecl gd, mlir::Operation *gv) {
   }
 }
 
+/// Get the feature delta from the default feature map for the given target CPU.
+static std::vector<std::string>
+getFeatureDeltaFromDefault(const CIRGenModule &cgm, llvm::StringRef targetCPU,
+                           llvm::StringMap<bool> &featureMap) {
+  llvm::StringMap<bool> defaultFeatureMap;
+  cgm.getTarget().initFeatureMap(
+      defaultFeatureMap, cgm.getASTContext().getDiagnostics(), targetCPU, {});
+
+  std::vector<std::string> delta;
+  for (const auto &[k, v] : featureMap) {
+    auto defaultIt = defaultFeatureMap.find(k);
+    if (defaultIt == defaultFeatureMap.end() || defaultIt->getValue() != v)
+      delta.push_back((v ? "+" : "-") + k.str());
+  }
+
+  return delta;
+}
+
+bool CIRGenModule::getCPUAndFeaturesAttributes(
+    GlobalDecl gd, llvm::StringMap<std::string> &attrs,
+    bool setTargetFeatures) {
+  // Add target-cpu and target-features attributes to functions. If
+  // we have a decl for the function and it has a target attribute then
+  // parse that and add it to the feature set.
+  llvm::StringRef targetCPU = getTarget().getTargetOpts().CPU;
+  llvm::StringRef tuneCPU = getTarget().getTargetOpts().TuneCPU;
+  std::vector<std::string> features;
+  const auto *fd = dyn_cast_or_null<FunctionDecl>(gd.getDecl());
+  fd = fd ? fd->getMostRecentDecl() : fd;
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bcardosolopes wrote:

Could use a one-liner explaining when `fd` is null here (i.e. globals without a FunctionDecl) — the AMDGPU branch later handles that case via `initFeatureMap`, but it's not obvious from reading top-down.

https://github.com/llvm/llvm-project/pull/193458