Refine autonaming to have more intuitive behavior (#1660)

* Refine autonaming to have more intuitive behavior

Last name in an Expression wins, while the first Statement to name wins.
This is done via checking the _id of HasIds during autonaming and only
applying a name if the HasId was created in the scope of autonaming.
There is no change to .autoSeed or .suggestName behavior.

Behavior of chisel3-plugins from before this change is maintained.

* Update docs with naming plugin changes

2 files changed, 55 insertions, 1 deletions

diff --git a/core/src/main/scala/chisel3/internal/Builder.scala b/core/src/main/scala/chisel3/internal/Builder.scala
index 56a85fb6..d665b7bc 100644
--- a/core/src/main/scala/chisel3/internal/Builder.scala
+++ b/core/src/main/scala/chisel3/internal/Builder.scala
@@ -59,6 +59,7 @@ private[chisel3] class IdGen {
     counter += 1
     counter
   }
+  def value: Long = counter
 }
 
 /** Public API to access Node/Signal names.
@@ -119,7 +120,9 @@ private[chisel3] trait HasId extends InstanceId {
     * @param seed Seed for the name of this component
     * @return this object
     */
-  private [chisel3] def autoSeed(seed: String): this.type = {
+  private[chisel3] def autoSeed(seed: String): this.type = forceAutoSeed(seed)
+  // Bypass the overridden behavior of autoSeed in [[Data]], apply autoSeed even to ports
+  private[chisel3] def forceAutoSeed(seed: String): this.type = {
     auto_seed = Some(seed)
     for(hook <- auto_postseed_hooks) { hook(seed) }
     prefix_seed = Builder.getPrefix()
diff --git a/core/src/main/scala/chisel3/internal/plugin/package.scala b/core/src/main/scala/chisel3/internal/plugin/package.scala
index dd091ccc..c17baf22 100644
--- a/core/src/main/scala/chisel3/internal/plugin/package.scala
+++ b/core/src/main/scala/chisel3/internal/plugin/package.scala
@@ -10,6 +10,7 @@ package object plugin {
     * @param nameMe The thing to be named
     * @tparam T The type of the thing to be named
     * @return The thing, but now named
+    * @note This is the version called by chisel3-plugin prior to v3.4.1
     */
   def autoNameRecursively[T <: Any](name: String, nameMe: T): T = {
     chisel3.internal.Builder.nameRecursively(
@@ -19,4 +20,54 @@ package object plugin {
     )
     nameMe
   }
+
+  // The actual implementation
+  // Cannot be unified with (String, T) => T (v3.4.0 version) because of special behavior of ports
+  // in .autoSeed
+  private def _autoNameRecursively[T <: Any](prevId: Long, name: String, nameMe: T): T = {
+    chisel3.internal.Builder.nameRecursively(
+      name,
+      nameMe,
+      (id: chisel3.internal.HasId, n: String) => {
+        // Name override only if result was created in this scope
+        if (id._id > prevId) {
+          id.forceAutoSeed(n)
+        }
+      }
+    )
+    nameMe
+  }
+
+  /** Used by Chisel's compiler plugin to automatically name signals
+    * DO NOT USE in your normal Chisel code!!!
+    *
+    * @param name The name to use
+    * @param nameMe The thing to be named
+    * @tparam T The type of the thing to be named
+    * @return The thing, but now named
+    */
+  def autoNameRecursively[T <: Any](name: String)(nameMe: => T): T = {
+    // The _id of the most recently constructed HasId
+    val prevId = Builder.idGen.value
+    val result = nameMe
+    _autoNameRecursively(prevId, name, result)
+  }
+
+  /** Used by Chisel's compiler plugin to automatically name signals
+    * DO NOT USE in your normal Chisel code!!!
+    *
+    * @param names The names to use corresponding to interesting fields of the Product
+    * @param nameMe The [[Product]] to be named
+    * @tparam T The type of the thing to be named
+    * @return The thing, but with each member named
+    */
+  def autoNameRecursivelyProduct[T <: Product](names: List[Option[String]])(nameMe: => T): T = {
+    // The _id of the most recently constructed HasId
+    val prevId = Builder.idGen.value
+    val result = nameMe
+    for ((name, t) <- names.iterator.zip(result.productIterator) if name.nonEmpty) {
+      _autoNameRecursively(prevId, name.get, t)
+    }
+    result
+  }
 }