[mlir][llvm] Handle llvm.noundef attribute when converting to LLVM IR

[victor-eds]

Summary

Translate LLVMIR llvm.noundef attribute to its equivalent in LLVM IR.

[ftynse]

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

920

Could we put the attribute name inside the dialect rather than hardcode the string here?

[victor-eds]

Add attribute name to the dialect

[victor-eds]

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

920

Done

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

let extraClassDeclaration = [{
     static StringRef getParallelAccessAttrName() { return "parallel_access"; }
     static StringRef getLoopOptionsAttrName() { return "options"; }
     static StringRef getAccessGroupsAttrName() { return "access_groups"; }
     static StringRef getStructAttrsAttrName() { return "llvm.struct_attrs"; }
     static StringRef getByValAttrName() { return "llvm.byval"; }
     static StringRef getByRefAttrName() { return "llvm.byref"; }
     static StringRef getStructRetAttrName() { return "llvm.sret"; }
     static StringRef getInAllocaAttrName() { return "llvm.inalloca"; }
+    static StringRef getNoUndefAttrName() { return "llvm.noundef"; }
 
     /// Verifies if the attribute is a well-formed value for "llvm.struct_attrs"
     static LogicalResult verifyStructAttr(
         Operation *op, Attribute attr, Type annotatedType);
 
     /// Verifies if the given string is a well-formed data layout descriptor.
     /// Uses `reportError` to report errors.
     static LogicalResult verifyDataLayoutString(

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

if (auto attr = func.getArgAttrOfType<UnitAttr>(argIdx, "llvm.nest")) {
       auto argTy = mlirArg.getType();
       if (!argTy.isa<LLVM::LLVMPointerType>())
         return func.emitError(
             "llvm.nest attribute attached to LLVM non-pointer argument");
       llvmArg.addAttrs(llvm::AttrBuilder(llvmArg.getContext())
                            .addAttribute(llvm::Attribute::Nest));
     }
 
+    if (auto attr = func.getArgAttrOfType<UnitAttr>(
+            argIdx, LLVMDialect::getNoUndefAttrName())) {
+      // llvm.noundef can be added to any argument type.
+      llvmArg.addAttrs(llvm::AttrBuilder(llvmArg.getContext())
+                           .addAttribute(llvm::Attribute::NoUndef));
+    }
+
     mapValue(mlirArg, &llvmArg);
     argIdx++;
   }
 
   // Check the personality and set it.
   if (func.getPersonality()) {
     llvm::Type *ty = llvm::Type::getInt8PtrTy(llvmFunc->getContext());
     if (llvm::Constant *pfunc = getLLVMConstant(ty, func.getPersonalityAttr(),

mlir/test/Target/LLVMIR/llvmir.mlir

llvm.func @sretattr(%arg0: !llvm.ptr<i32> {llvm.sret = i32}) {
   llvm.return
 }
 
 // CHECK-LABEL: define void @nestattr(ptr nest %
 llvm.func @nestattr(%arg0: !llvm.ptr<i32> {llvm.nest}) {
   llvm.return
 }
 
+// CHECK-LABEL: define void @noundefattr(i32 noundef %
+llvm.func @noundefattr(%arg0: i32 {llvm.noundef}) {
+  llvm.return
+}
+
 // CHECK-LABEL: define void @llvm_align(ptr align 4 {{%*.}})
 llvm.func @llvm_align(%arg0: !llvm.ptr<f32> {llvm.align = 4}) {
   llvm.return
 }
 
 // CHECK-LABEL: @llvm_varargs(...)
 llvm.func @llvm_varargs(...)