[MLIR] Add LocationAttr declarations to ODS

[youngar]

Summary

This commit adds location attributes and arrays of locations to OpBase.td. Using LocationAttrs directly in an operation is useful when the location does not correspond 1-1 to an operation or value in the IR. We use this in CIRCT to store the declaration location of result ports of HWModule operations.

[youngar]

My old patch was generated with --no-prefix, which seems to have confused phabricator, and lead to the CI failures.

[jpienaar]

I'm actually surprised we didn't have this one, thanks, let know if you need help landing.

mlir/include/mlir/IR/OpBase.td

class AnyAttrOf<list<Attr> allowedAttrs, string summary = "",
     Or<!foreach(allowedattr, allowedAttrs, allowedattr.predicate)>,
     !if(!eq(summary, ""),
         !interleave(!foreach(t, allowedAttrs, t.summary), " or "),
         summary)> {
     let returnType = cppClassName;
     let convertFromStorage = fromStorage;
 }
 
+def LocationAttr : Attr<CPred<"$_self.isa<::mlir::LocationAttr>()">,
+                        "location attribute">;
+
 def BoolAttr : Attr<CPred<"$_self.isa<::mlir::BoolAttr>()">, "bool attribute"> {
   let storageType = [{ ::mlir::BoolAttr }];
   let returnType = [{ bool }];
   let valueType = I1;
   let constBuilderCall = "$_builder.getBoolAttr($0)";
 }
 
 // Index attribute.
And<[
                             "[&](::mlir::Attribute attr) { return attr && (",
                                SubstLeaves<"$_self", "attr", element.predicate>,
                             "); })">]>,
     summary> {
 
   Attr elementAttr = element;
 }
 
+def LocationArrayAttr : TypedArrayAttrBase<LocationAttr,
+                                           "location array attribute">;
+
 def AffineMapArrayAttr : TypedArrayAttrBase<AffineMapAttr,
                                       "AffineMap array attribute"> {
   let constBuilderCall = "$_builder.getAffineMapArrayAttr($0)";
 }
 
 def BoolArrayAttr : TypedArrayAttrBase<BoolAttr,
                                       "1-bit boolean array attribute"> {
   let constBuilderCall = "$_builder.getBoolArrayAttr($0)";