Enhance views to [sometimes] support dynamic indexing and implement FlatIO (backport #2476) (#2479)

* Capture 1:1 mappings of Aggregates inside of views

This is implemented by including any corresponding Aggregates from the
DataView.mapping in the AggregateViewBinding.childMap (which is now of
type Map[Data, Data]).

This enables dynamically indexing Vecs that are themselves elements of
larger Aggregates in views when the corresponding element of the view is
a Vec of the same type. It also increases the number of cases where a
single Target can represent part of a view.

(cherry picked from commit 1f6b1ca14ccf86918065073c3f6f3626dd83a68e)

* Add FlatIO API for creating ports from Bundles without a prefix

(cherry picked from commit 772a3a1fe3b9372b7c2d7cd2d424b2adcd633cdb)

* [docs] Add FlatIO to the general cookbook

(cherry picked from commit b4159641350f238f0f899b69954142ce8ee11544)

Co-authored-by: Jack Koenig <koenig@sifive.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/core/src/main/scala/chisel3/Element.scala b/core/src/main/scala/chisel3/Element.scala
index 401f2bdf..39b7689c 100644
--- a/core/src/main/scala/chisel3/Element.scala
+++ b/core/src/main/scala/chisel3/Element.scala
@@ -36,10 +36,15 @@ abstract class Element extends Data {
         case Some(litArg) => Some(ElementLitBinding(litArg))
         case _            => Some(DontCareBinding())
       }
-    case Some(b @ AggregateViewBinding(viewMap, _)) =>
+    // TODO Do we even need this? Looking up things in the AggregateViewBinding is fine
+    case Some(b @ AggregateViewBinding(viewMap)) =>
       viewMap.get(this) match {
-        case Some(elt) => Some(ViewBinding(elt))
-        case _         => throwException(s"Internal Error! $this missing from topBinding $b")
+        case Some(elt: Element) => Some(ViewBinding(elt))
+        // TODO We could generate a reduced AggregateViewBinding, but is there a point?
+        // Generating the new object would be somewhat slow, it's not clear if we should do this
+        //   matching anyway
+        case Some(data: Aggregate) => Some(b)
+        case _ => throwException(s"Internal Error! $this missing from topBinding $b")
       }
     case topBindingOpt => topBindingOpt
   }