Fix invalid references generated by VerilogMemDelays (#2588)

Transformation of mem readwriters whose address contain references to
readwriters of mems declared before it would contain invalid references
to untransformed memory readwriter, as the connection is not transformed.
This commit fixes this issue.

src/main/scala/firrtl/passes/memlib/VerilogMemDelays.scala

@@ -221,7 +221,18 @@ class MemDelayAndReadwriteTransformer(m: DefModule, passthroughSimpleSyncReadMem
   val transformed = m match {
     case mod: Module =>
       findMemConns(mod.body)
-      mod.copy(body = Block(transform(mod.body) +: newConns.toSeq))
+      val bodyx = transform(mod.body)
+      // Fixup any mem connections being driven by other transformed memories
+      val newConsx = newConns.map {
+        case sx if kind(sx.loc) == MemKind =>
+          val (memRef, _) = Utils.splitRef(sx.loc)
+          if (passthroughMems(WrappedExpression(memRef)))
+            sx
+          else
+            sx.mapExpr(swapMemRefs)
+        case sx => sx
+      }
+      mod.copy(body = Block(bodyx +: newConsx.toSeq))
     case mod => mod
   }
 }

src/test/scala/firrtlTests/VerilogMemDelaySpec.scala

@@ -188,4 +188,62 @@ class VerilogMemDelaySpec extends LeanTransformSpec(Seq(Dependency(VerilogMemDel
     res should include("m.write.clk <= clock")
     res should include("reg m_write_data_pipe_0 : UInt<8>, clock")
   }
+
+  it should "VerilogMemDelays should replace expr in connections of previous mems" in {
+    val input =
+      """
+        |circuit Test :
+        |  module Test :
+        |    input clock : Clock
+        |    input sel : UInt<1>
+        |    input en : UInt<1>
+        |    output v1 : UInt<1>
+        |    output v2 : UInt<1>
+        |
+        |    mem m1 :
+        |      data-type => UInt<1>
+        |      depth => 2
+        |      read-latency => 0
+        |      write-latency => 1
+        |      readwriter => rw1
+        |      readwriter => rw2
+        |      read-under-write => undefined
+        |    mem m2 :
+        |      data-type => UInt<1>
+        |      depth => 2
+        |      read-latency => 0
+        |      write-latency => 1
+        |      readwriter => rw1
+        |      readwriter => rw2
+        |      read-under-write => undefined
+        |    v1 <= m1.rw2.rdata
+        |    v2 <= m2.rw2.rdata
+        |    m1.rw1.addr <= UInt<1>("h0")
+        |    m2.rw1.addr <= UInt<1>("h0")
+        |    m1.rw1.en <= UInt<1>("h1")
+        |    m2.rw1.en <= UInt<1>("h1")
+        |    m1.rw1.clk <= clock
+        |    m2.rw1.clk <= clock
+        |    m1.rw1.wmode <= en
+        |    m2.rw1.wmode <= en
+        |    m1.rw1.wdata <= UInt<1>("h1")
+        |    m2.rw1.wdata <= UInt<1>("h0")
+        |    m1.rw1.wmask <= en
+        |    m2.rw1.wmask <= UInt<1>("h0")
+        |    m1.rw2.addr <= m2.rw1.rdata
+        |    m2.rw2.addr <= m2.rw1.rdata
+        |    m1.rw2.en <= UInt<1>("h1")
+        |    m2.rw2.en <= UInt<1>("h1")
+        |    m1.rw2.clk <= clock
+        |    m2.rw2.clk <= clock
+        |    m1.rw2.wmode <= en
+        |    m2.rw2.wmode <= en
+        |    m1.rw2.wdata <= UInt<1>("h0")
+        |    m2.rw2.wdata <= UInt<1>("h0")
+        |    m1.rw2.wmask <= en
+        |    m2.rw2.wmask <= UInt<1>("h0")
+      """.stripMargin
+
+    compileTwice(input)
+  }
 }