[mlir] Add support for the nest attribute to the LLVM-IR dialect conversion.

[clementval]

LGTM. Can you just fix the clang-format issue?

[ftynse]

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

865–866

Ideally, we would move these to the verifier of the LLVM dialect. Given the consistency with the other attributes, this is something to do in a separate patch.

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

if (auto attr = func.getArgAttrOfType<UnitAttr>(argIdx, "llvm.byval")) {
       auto argTy = mlirArg.getType().dyn_cast<LLVM::LLVMPointerType>();
       if (!argTy)
         return func.emitError(
             "llvm.byval attribute attached to LLVM non-pointer argument");
       llvmArg.addAttrs(llvm::AttrBuilder(llvmArg.getContext())
                            .addByValAttr(convertType(argTy.getElementType())));
     }
 
+    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));
+    }
+
     mapValue(mlirArg, &llvmArg);
     argIdx++;
   }
 
   // Check the personality and set it.
   if (func.getPersonality().hasValue()) {
     llvm::Type *ty = llvm::Type::getInt8PtrTy(llvmFunc->getContext());
     if (llvm::Constant *pfunc = getLLVMConstant(ty, func.getPersonalityAttr(),

mlir/test/Dialect/LLVMIR/func.mlir

llvm.func @byvalattr(%arg0: !llvm.ptr<i32> {llvm.byval}) {
     llvm.return
   }
 
   // CHECK: llvm.func @sretattr(%{{.*}}: !llvm.ptr<i32> {llvm.sret})
   llvm.func @sretattr(%arg0: !llvm.ptr<i32> {llvm.sret}) {
     llvm.return
   }
 
+  // CHECK: llvm.func @nestattr(%{{.*}}: !llvm.ptr<i32> {llvm.nest})
+  llvm.func @nestattr(%arg0: !llvm.ptr<i32> {llvm.nest}) {
+    llvm.return
+  }
+
   // CHECK: llvm.func @variadic(...)
   llvm.func @variadic(...)
 
   // CHECK: llvm.func @variadic_args(i32, i32, ...)
   llvm.func @variadic_args(i32, i32, ...)
 
   //
   // Check that functions can have linkage attributes.

mlir/test/Target/LLVMIR/llvmir-invalid.mlir

 // expected-error @+1 {{llvm.noalias attribute attached to LLVM non-pointer argument}}
 llvm.func @invalid_noalias(%arg0 : f32 {llvm.noalias}) -> f32 {
   llvm.return %arg0 : f32
 }
 
 // -----
 
 // expected-error @+1 {{llvm.sret attribute attached to LLVM non-pointer argument}}
-llvm.func @invalid_noalias(%arg0 : f32 {llvm.sret}) -> f32 {
+llvm.func @invalid_sret(%arg0 : f32 {llvm.sret}) -> f32 {
+  llvm.return %arg0 : f32
+}
+
+// -----
+
+// expected-error @+1 {{llvm.nest attribute attached to LLVM non-pointer argument}}
+llvm.func @invalid_nest(%arg0 : f32 {llvm.nest}) -> f32 {
   llvm.return %arg0 : f32
 }
 // -----
 
 // expected-error @+1 {{llvm.byval attribute attached to LLVM non-pointer argument}}
-llvm.func @invalid_noalias(%arg0 : f32 {llvm.byval}) -> f32 {
+llvm.func @invalid_byval(%arg0 : f32 {llvm.byval}) -> f32 {
   llvm.return %arg0 : f32
 }
 
 // -----
 
 // expected-error @+1 {{llvm.align attribute attached to LLVM non-pointer argument}}
 llvm.func @invalid_align(%arg0 : f32 {llvm.align = 4}) -> f32 {
   llvm.return %arg0 : f32

mlir/test/Target/LLVMIR/llvmir.mlir

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