Use AArch64 assembly syntax on macOS with LLVM<22 (#8710)

Author: alexreinking

src/CodeGen_Internal.cpp

@@ -670,6 +670,16 @@ std::unique_ptr<llvm::TargetMachine> make_target_machine(const llvm::Module &mod
     std::string mattrs =
         get_md_string(module.getModuleFlag("halide_mattrs")).value_or(std::string{});
 
+#if LLVM_VERSION < 200
+    if (triple.isMacOSX() && triple.isAArch64()) {
+        // The generic syntax variant is able to display the arguments to SDOT
+        // while the Apple-specific one is bugged. See this GitHub issue for
+        // more info: https://github.com/llvm/llvm-project/issues/151330
+        const char *args[] = {"llc", "-aarch64-neon-syntax=generic"};
+        cl::ParseCommandLineOptions(2, args, "Halide compiler\n");
+    }
+#endif
+
     auto *tm = llvm_target->createTargetMachine(
 #if LLVM_VERSION >= 210
         triple,

src/LLVM_Output.cpp

@@ -388,7 +388,8 @@ void emit_file(const llvm::Module &module_in, Internal::LLVMOStream &out,
     // https://groups.google.com/g/llvm-dev/c/HoS07gXx0p8
     llvm::legacy::PassManager pass_manager;
 
-    pass_manager.add(new llvm::TargetLibraryInfoWrapperPass(llvm::Triple(module->getTargetTriple())));
+    const auto &triple = llvm::Triple(module->getTargetTriple());
+    pass_manager.add(new llvm::TargetLibraryInfoWrapperPass(triple));
 
     // Make sure things marked as always-inline get inlined
     pass_manager.add(llvm::createAlwaysInlinerLegacyPass());
@@ -400,6 +401,17 @@ void emit_file(const llvm::Module &module_in, Internal::LLVMOStream &out,
     // Override default to generate verbose assembly.
     target_machine->Options.MCOptions.AsmVerbose = true;
 
+#if 200 <= LLVM_VERSION && LLVM_VERSION < 220
+    if (triple.isMacOSX() && triple.isAArch64()) {
+        // The AArch64 syntax variant is able to display the arguments to SDOT
+        // while the Darwin-specific one is bugged. See this GitHub issue for
+        // more info: https://github.com/llvm/llvm-project/issues/151330
+        enum { Generic = 0,
+               Apple = 1 } variant = Generic;
+        target_machine->Options.MCOptions.OutputAsmVariant = variant;
+    }
+#endif
+
     // Ask the target to add backend passes as necessary.
     target_machine->addPassesToEmitFile(pass_manager, out, nullptr, file_type);