[MLIR][OpenMP] Add omp.target_triples attribute to the OffloadModuleInterface

The `OffloadModuleInterface` holds getter/setter methods to access OpenMP
dialect module-level discardable attributes used to hold general OpenMP
compilation information.

This patch adds the `omp.target_triples` attribute, which is intended to hold
the list of offloading target triples linked to the host module in which it
appears. This attribute should be empty when `omp.is_target_device=true`.

Author: skatrak

mlir/include/mlir/Dialect/OpenMP/OpenMPOpsInterfaces.td

@@ -351,6 +351,34 @@ def OffloadModuleInterface : OpInterface<"OffloadModuleInterface"> {
       (ins "::mlir::omp::ClauseRequires":$clauses), [{}], [{
         $_op->setAttr(mlir::StringAttr::get($_op->getContext(), "omp.requires"),
           mlir::omp::ClauseRequiresAttr::get($_op->getContext(), clauses));
+      }]>,
+    InterfaceMethod<
+      /*description=*/[{
+        Get the omp.target_triples attribute on the operator if it's present and
+        return its value. If it doesn't exist, return an empty array by default.
+      }],
+      /*retTy=*/"::llvm::ArrayRef<::mlir::Attribute>",
+      /*methodName=*/"getTargetTriples",
+      (ins), [{}], [{
+        if (Attribute triplesAttr = $_op->getAttr("omp.target_triples"))
+          if (auto triples = ::llvm::dyn_cast<::mlir::ArrayAttr>(triplesAttr))
+            return triples.getValue();
+        return {};
+      }]>,
+    InterfaceMethod<
+      /*description=*/[{
+        Set the omp.target_triples attribute on the operation.
+      }],
+      /*retTy=*/"void",
+      /*methodName=*/"setTargetTriples",
+      (ins "::llvm::ArrayRef<::std::string>":$targetTriples), [{}], [{
+        auto names = ::llvm::to_vector(::llvm::map_range(
+            targetTriples, [&](::std::string str) -> ::mlir::Attribute {
+              return mlir::StringAttr::get($_op->getContext(), str);
+            }));
+        $_op->setAttr(
+            ::mlir::StringAttr::get($_op->getContext(), "omp.target_triples"),
+            ::mlir::ArrayAttr::get($_op->getContext(), names));
       }]>
   ];
 }