Fix lookup succeeding on invalid entry; add test case

also enable VCS FSDB annotation in chiseltest

src/main/scala/tilelink/Coalescing.scala

@@ -258,9 +258,10 @@ class InflightCoalReqTable(
     // If entry with a lower index is empty, it always takes priority
     cascadeMatchIndex(i) := Mux(match_, i.U, cascadeMatchIndex(i + 1))
   }
-  val matchIndex = cascadeMatchIndex(0)
+  val matchIndex = Wire(UInt())
-  val matchValid = Wire(Bool())
+  matchIndex := cascadeMatchIndex(0)
-  matchValid := table(matchIndex).bits.respSourceId === io.lookupSourceId
+  val matchValid = table(matchIndex).valid &&
+    (table(matchIndex).bits.respSourceId === io.lookupSourceId)
   io.lookup.valid := matchValid
   // TODO: return something actually useful
   io.lookup.bits := table(matchIndex).bits.respSourceId
@@ -272,7 +273,6 @@ class InflightCoalReqTable(
   }
   dontTouch(io.lookup)
   dontTouch(matchIndex)
-  dontTouch(matchValid)
 }
 
 class InflightCoalReqTableEntry(val numLanes: Int, val sourceWidth: Int)

src/test/scala/CoalescingUnitTest.scala

@@ -38,19 +38,64 @@ class CoalescingUnitTest extends AnyFlatSpec with ChiselScalatestTester {
   val inflightCoalReqTableEntry =
     new InflightCoalReqTableEntry(numLanes, sourceWidth)
 
-  it should "whatever" in {
+  it should "stop enqueueing when full" in {
     test(new InflightCoalReqTable(numLanes, sourceWidth, entries)) { c =>
-      // val tableEntry = new InflightCoalReqTableEntry(numLanes, sourceWidth)
+      for (i <- 0 until entries) {
-      val respSourceId = 0.U
+        c.io.enq.ready.expect(true.B)
+        c.io.enq.valid.poke(true.B)
+        c.io.enq.bits.fromLane.poke(0.U)
+        c.io.enq.bits.respSourceId.poke(i.U)
+        c.io.enq.bits.reqSourceIds.foreach { id => id.poke(0.U) }
+
+        c.clock.step()
+      }
+
+      c.io.enq.ready.expect(false.B)
       c.io.enq.valid.poke(true.B)
       c.io.enq.bits.fromLane.poke(0.U)
-      c.io.enq.bits.respSourceId.poke(respSourceId)
+      c.io.enq.bits.respSourceId.poke(0.U)
       c.io.enq.bits.reqSourceIds.foreach { id => id.poke(0.U) }
+
       c.clock.step()
-      c.io.lookup.ready.poke(true.B)
+      c.io.enq.ready.expect(false.B)
-      c.io.lookupSourceId.poke(respSourceId)
-      c.io.lookup.valid.expect(true.B)
-      c.io.lookup.bits.expect(respSourceId)
     }
   }
+  it should "lookup matching entry" in {
+    test(new InflightCoalReqTable(numLanes, sourceWidth, entries))
+      .withAnnotations(Seq(VcsBackendAnnotation, WriteFsdbAnnotation)) { c =>
+        c.reset.poke(true.B)
+        c.clock.step(10)
+        c.reset.poke(false.B)
+
+        // enqueue one entry to not match at 0th index
+        c.io.enq.ready.expect(true.B)
+        c.io.enq.valid.poke(true.B)
+        c.io.enq.bits.fromLane.poke(0.U)
+        c.io.enq.bits.respSourceId.poke(0.U)
+        c.io.enq.bits.reqSourceIds.foreach { id => id.poke(0.U) }
+
+        c.clock.step()
+
+        val targetSourceId = 1.U
+        c.io.enq.ready.expect(true.B)
+        c.io.enq.valid.poke(true.B)
+        c.io.enq.bits.fromLane.poke(0.U)
+        c.io.enq.bits.respSourceId.poke(targetSourceId)
+        c.io.enq.bits.reqSourceIds.foreach { id => id.poke(0.U) }
+
+        c.clock.step()
+
+        c.io.lookup.ready.poke(true.B)
+        c.io.lookupSourceId.poke(targetSourceId)
+        c.io.lookup.valid.expect(true.B)
+        c.io.lookup.bits.expect(targetSourceId)
+
+        c.clock.step()
+
+        // test if matching entry dequeues after 1 cycle
+        c.io.lookup.ready.poke(true.B)
+        c.io.lookupSourceId.poke(targetSourceId)
+        c.io.lookup.valid.expect(false.B)
+      }
+  }
 }