[clang] [llvm] [LLVM][Clang][AArch64] Implement AArch64 build attributes (PR #118771)

[via llvm-commits]

================
@@ -151,3 +151,97 @@ llvm::createAArch64ObjectTargetStreamer(MCStreamer &S,
 MCTargetStreamer *llvm::createAArch64NullTargetStreamer(MCStreamer &S) {
   return new AArch64TargetStreamer(S);
 }
+
+void AArch64TargetStreamer::emitAtributesSubsection(
+    StringRef VendorName, AArch64BuildAttributes::SubsectionOptional IsOptional,
+    AArch64BuildAttributes::SubsectionType ParameterType) {
+
+  // If exists, return.
+  for (MCELFStreamer::AttributeSubSection &SubSection : AttributeSubSections) {
+    if (VendorName == SubSection.VendorName) {
+      activateAtributesSubsection(VendorName);
+      return;
+    }
+  }
+  // else, add the subsection
+  MCELFStreamer::AttributeSubSection AttSubSection;
+  AttSubSection.VendorName = VendorName;
+  AttSubSection.IsOptional = IsOptional;
+  AttSubSection.ParameterType = ParameterType;
+  AttributeSubSections.push_back(AttSubSection);
+  activateAtributesSubsection(VendorName);
+}
+
+std::unique_ptr<MCELFStreamer::AttributeSubSection>
+AArch64TargetStreamer::getActiveAtributesSubsection() {
+  for (MCELFStreamer::AttributeSubSection &SubSection : AttributeSubSections) {
+    if (SubSection.IsActive) {
+      return std::make_unique<MCELFStreamer::AttributeSubSection>(SubSection);
+    }
+  }
+  return nullptr;
+}
+
+void AArch64TargetStreamer::emitAttribute(StringRef VendorName, unsigned Tag,
+                                          unsigned Value, std::string String,
+                                          bool Override) {
+
+  if (unsigned(-1) == Value && "" == String) {
+    assert(0 && "Arguments error");
+    return;
+  }
+  if (AttributeSubSections.size() == 0) {
+    assert(0 &&
+           "Can not add AArch64 build attribute: no AArch64 subsection exists");
+    return;
+  }
+
+  for (MCELFStreamer::AttributeSubSection &SubSection : AttributeSubSections) {
+    if (VendorName == SubSection.VendorName) {
+      if (!SubSection.IsActive) {
+        assert(0 &&
+               "Can not add AArch64 build attribute: subsection is not active");
+        return;
+      }
+      for (MCELFStreamer::AttributeItem &Item : SubSection.Content) {
+        if (Item.Tag == Tag) {
+          if (!Override) {
+            if ((unsigned(-1) != Value && Item.IntValue != Value) ||
----------------
sivan-shani wrote:

The if/else capture 2 different cases, and gives an appropriate debug message accordingly.
The value out of it is:
1. proper debug message, which is helpful.
2. readability, clarifying why the return is happening.
Having this seems better then not, even though it is possible to reduce a bit of code.

https://github.com/llvm/llvm-project/pull/118771