Fix chisel3 <> for Bundles that contain compatibility Bundles (#2023)

BiConnect in chisel3 delegates to FIRRTL <- semantics whenever it hits a
Bundle defined in `import Chisel._`. Because chisel3 <> is commutative
it needs to be mindful of flippedness when emitting a FIRRTL <- (which
is *not* commutative).

2 files changed, 55 insertions, 8 deletions

diff --git a/core/src/main/scala/chisel3/internal/BiConnect.scala b/core/src/main/scala/chisel3/internal/BiConnect.scala
index 1ee149ee..fcea4fe2 100644
--- a/core/src/main/scala/chisel3/internal/BiConnect.scala
+++ b/core/src/main/scala/chisel3/internal/BiConnect.scala
@@ -113,14 +113,23 @@ private[chisel3] object BiConnect {
           }
         }
       }
-      // Handle Records defined in Chisel._ code (change to NotStrict)
-      case (left_r: Record, right_r: Record) => (left_r.compileOptions, right_r.compileOptions) match {
-        case (ExplicitCompileOptions.NotStrict, _) =>
-          left_r.bulkConnect(right_r)(sourceInfo, ExplicitCompileOptions.NotStrict)
-        case (_, ExplicitCompileOptions.NotStrict) =>
-          left_r.bulkConnect(right_r)(sourceInfo, ExplicitCompileOptions.NotStrict)
-        case _ => recordConnect(sourceInfo, connectCompileOptions, left_r, right_r, context_mod)
-      }
+      // Handle Records defined in Chisel._ code by emitting a FIRRTL partial connect
+      case pair @ (left_r: Record, right_r: Record) =>
+        val notStrict =
+          Seq(left_r.compileOptions, right_r.compileOptions).contains(ExplicitCompileOptions.NotStrict)
+        if (notStrict) {
+          // chisel3 <> is commutative but FIRRTL <- is not
+          val flipped = {
+            // Everything is flipped when it's the port of a child
+            val childPort = left_r._parent.get != context_mod
+            val isFlipped = left_r.direction == ActualDirection.Bidirectional(ActualDirection.Flipped)
+            isFlipped ^ childPort
+          }
+          val (newLeft, newRight) = if (flipped) pair.swap else pair
+          newLeft.bulkConnect(newRight)(sourceInfo, ExplicitCompileOptions.NotStrict)
+        } else {
+          recordConnect(sourceInfo, connectCompileOptions, left_r, right_r, context_mod)
+        }
 
       // Handle Records connected to DontCare (change to NotStrict)
       case (left_r: Record, DontCare) =>
diff --git a/src/test/scala/chiselTests/CompatibilityInteroperabilitySpec.scala b/src/test/scala/chiselTests/CompatibilityInteroperabilitySpec.scala
index cfcc4608..8e9f9e7e 100644
--- a/src/test/scala/chiselTests/CompatibilityInteroperabilitySpec.scala
+++ b/src/test/scala/chiselTests/CompatibilityInteroperabilitySpec.scala
@@ -289,5 +289,43 @@ class CompatibiltyInteroperabilitySpec extends ChiselFlatSpec {
       }
     }
   }
+
+  "A chisel3 Bundle that instantiates a Chisel Bundle" should "bulk connect correctly" in {
+    compile {
+      object Compat {
+        import Chisel._
+        class Foo extends Bundle {
+          val a = Input(UInt(8.W))
+          val b = Output(UInt(8.W))
+        }
+      }
+      import chisel3._
+      import Compat._
+      class Bar extends Bundle {
+        val foo1 = new Foo
+        val foo2 = Flipped(new Foo)
+      }
+      // Check every connection both ways to see that chisel3 <>'s commutativity holds
+      class Child extends RawModule {
+        val deq = IO(new Bar)
+        val enq = IO(Flipped(new Bar))
+        enq <> deq
+        deq <> enq
+      }
+      new RawModule {
+        val deq = IO(new Bar)
+        val enq = IO(Flipped(new Bar))
+        // Also important to check connections to child ports
+        val c1 = Module(new Child)
+        val c2 = Module(new Child)
+        c1.enq <> enq
+        enq <> c1.enq
+        c2.enq <> c1.deq
+        c1.deq <> c2.enq
+        deq <> c2.deq
+        c2.deq <> deq
+      }
+    }
+  }
 }