[mlir][llvm] Expose getters for alias and align attribute names

[herhut]

Summary

This adds getters for llvm.align and llvm.noalias strings that are used
as attribute names in the llvm dialect.

mlir/include/mlir/Dialect/LLVMIR/LLVMOpBase.td

def LLVM_Dialect : Dialect {
   let name = "llvm";
   let cppNamespace = "::mlir::LLVM";
 
   let hasRegionArgAttrVerify = 1;
   let hasOperationAttrVerify = 1;
   let extraClassDeclaration = [{
     /// Name of the data layout attributes.
     static StringRef getDataLayoutAttrName() { return "llvm.data_layout"; }
+    static StringRef getAlignAttrName() { return "llvm.align"; }
+    static StringRef getNoAliasAttrName() { return "llvm.noalias"; }
 
     /// Verifies if the given string is a well-formed data layout descriptor.
     /// Uses `reportError` to report errors.
     static LogicalResult verifyDataLayoutString(
         StringRef descr, llvm::function_ref<void (const Twine &)> reportError);
   }];
 }
 

mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp

 }
 
 /// Verify LLVMIR function argument attributes.
 LogicalResult LLVMDialect::verifyRegionArgAttribute(Operation *op,
                                                     unsigned regionIdx,
                                                     unsigned argIdx,
                                                     NamedAttribute argAttr) {
   // Check that llvm.noalias is a boolean attribute.
-  if (argAttr.first == "llvm.noalias" && !argAttr.second.isa<BoolAttr>())
+  if (argAttr.first == LLVMDialect::getNoAliasAttrName() &&
+      !argAttr.second.isa<BoolAttr>())
     return op->emitError()
            << "llvm.noalias argument attribute of non boolean type";
   // Check that llvm.align is an integer attribute.
-  if (argAttr.first == "llvm.align" && !argAttr.second.isa<IntegerAttr>())
+  if (argAttr.first == LLVMDialect::getAlignAttrName() &&
+      !argAttr.second.isa<IntegerAttr>())
     return op->emitError()
            << "llvm.align argument attribute of non integer type";
   return success();
 }
 
 //===----------------------------------------------------------------------===//
 // Utility functions.
 //===----------------------------------------------------------------------===//

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

LogicalResult ModuleTranslation::convertOneFunction(LLVMFuncOp func) {
 
   // Add function arguments to the value remapping table.
   // If there was noalias info then we decorate each argument accordingly.
   unsigned int argIdx = 0;
   for (auto kvp : llvm::zip(func.getArguments(), llvmFunc->args())) {
     llvm::Argument &llvmArg = std::get<1>(kvp);
     BlockArgument mlirArg = std::get<0>(kvp);
 
-    if (auto attr = func.getArgAttrOfType<BoolAttr>(argIdx, "llvm.noalias")) {
+    if (auto attr = func.getArgAttrOfType<BoolAttr>(
+            argIdx, LLVMDialect::getNoAliasAttrName())) {
       // NB: Attribute already verified to be boolean, so check if we can indeed
       // attach the attribute to this argument, based on its type.
       auto argTy = mlirArg.getType().dyn_cast<LLVM::LLVMType>();
       if (!argTy.isPointerTy())
         return func.emitError(
             "llvm.noalias attribute attached to LLVM non-pointer argument");
       if (attr.getValue())
         llvmArg.addAttr(llvm::Attribute::AttrKind::NoAlias);
     }
 
-    if (auto attr = func.getArgAttrOfType<IntegerAttr>(argIdx, "llvm.align")) {
+    if (auto attr = func.getArgAttrOfType<IntegerAttr>(
+            argIdx, LLVMDialect::getAlignAttrName())) {
       // NB: Attribute already verified to be int, so check if we can indeed
       // attach the attribute to this argument, based on its type.
       auto argTy = mlirArg.getType().dyn_cast<LLVM::LLVMType>();
       if (!argTy.isPointerTy())
         return func.emitError(
             "llvm.align attribute attached to LLVM non-pointer argument");
       llvmArg.addAttrs(
           llvm::AttrBuilder().addAlignmentAttr(llvm::Align(attr.getInt())));