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

[Oliver Stannard via llvm-commits]

================
@@ -7806,6 +7815,267 @@ bool AArch64AsmParser::parseDirectiveSEHSaveAnyReg(SMLoc L, bool Paired,
   return false;
 }
 
+bool AArch64AsmParser::parseDirectiveAeabiSubSectionHeader(SMLoc L) {
+  // Expecting 3 AsmToken::Identifier after '.aeabi_subsection', a name and 2
+  // parameters, e.g.: .aeabi_subsection (1)aeabi_feature_and_bits, (2)optional,
+  // (3)uleb128 separated by 2 commas.
+  MCAsmParser &Parser = getParser();
+
+  bool HasActiveSubsection = true;
+  std::unique_ptr<MCELFStreamer::AttributeSubSection> ActiveSubsection =
+      getTargetStreamer().getActiveAtributesSubsection();
+  if (nullptr == ActiveSubsection) {
+    HasActiveSubsection = false;
+  }
+
+  // Consume the name (subsection name)
+  StringRef SubsectionName;
+  AArch64BuildAttributes::VendorID SubsectionNameID;
+  if (Parser.getTok().is(AsmToken::Identifier)) {
+    SubsectionName = Parser.getTok().getIdentifier();
+    SubsectionNameID = AArch64BuildAttributes::getVendorID(SubsectionName);
+  } else {
+    Error(Parser.getTok().getLoc(), "subsection name not found");
+    return true;
+  }
+  Parser.Lex();
+  // consume a comma
+  // parseComma() return *false* on success, and call Lex(), no need to call
+  // Lex() again.
+  if (Parser.parseComma()) {
+    return true;
+  }
+
+  // Consume the first parameter (optionality parameter)
+  AArch64BuildAttributes::SubsectionOptional IsOptional;
+  // options: optional/required
+  if (Parser.getTok().is(AsmToken::Identifier)) {
+    StringRef Optionality = Parser.getTok().getIdentifier();
+    IsOptional = AArch64BuildAttributes::getOptionalID(Optionality);
+    if (AArch64BuildAttributes::OPTIONAL_NOT_FOUND == IsOptional) {
+      Error(Parser.getTok().getLoc(),
+            AArch64BuildAttributes::getSubsectionOptionalUnknownError() + ": " +
+                Optionality);
+      return true;
+    }
+    if (HasActiveSubsection &&
----------------
ostannard wrote:

This won't catch mis-matches with unknown subsection names which are not currently active. For example:
```
.aeabi_subsection foo, optional, uleb128
.aeabi_subsection bar, optional, uleb128
.aeabi_subsection foo, required, uleb128 // should be error, subsection `foo` was previously defined as optional
```

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