Add isOneOf method to ChiselEnum (#1966)

* Add @ekiwi's code as a starting point

* Add test for ChiselEnum isOneOf method

* Make isOneOfTester naming consistent with other testers

* Add scaladoc comments for isOneOf

* Add isOneOf tests that use the method that takes variable number of args

* Add guide level documentation example for isOneOf

core/src/main/scala/chisel3/StrongEnum.scala

@@ -135,6 +135,24 @@ abstract class EnumType(private val factory: EnumFactory, selfAnnotating: Boolea
     }
   }
 
+  /** Test if this enumeration is equal to any of the values in a given sequence
+    *
+    * @param s a [[scala.collection.Seq$ Seq]] of enumeration values to look for
+    * @return a hardware [[Bool]] that indicates if this value matches any of the given values
+    */
+  final def isOneOf(s: Seq[EnumType])(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool = {
+    VecInit(s.map(this === _)).asUInt().orR()
+  }
+
+  /** Test if this enumeration is equal to any of the values given as arguments
+    *
+    * @param u1 the first value to look for
+    * @param u2 zero or more additional values to look for
+    * @return a hardware [[Bool]] that indicates if this value matches any of the given values
+    */
+  final def isOneOf(u1: EnumType, u2: EnumType*)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): Bool
+    = isOneOf(u1 +: u2.toSeq)
+
   def next(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): this.type = {
     if (litOption.isDefined) {
       val index = factory.all.indexOf(this)

docs/src/explanations/chisel-enum.md

@@ -182,6 +182,25 @@ def expectedSel(sel: AluMux1Sel.Type): Boolean = sel match {
 }
 ```
 
+The enum value type also defines some convenience methods for working with `ChiselEnum` values. For example, continuing with the RISC-V opcode
+example, one could easily create hardware signal that is only asserted on LOAD/STORE operations (when the enum value is equal to `Opcode.load`
+or `Opcode.store`) using the `.isOneOf` method:
+
+```scala mdoc
+class LoadStoreExample extends Module {
+  val io = IO(new Bundle {
+    val opcode = Input(Opcode())
+    val load_or_store = Output(Bool())
+  })
+  io.load_or_store := io.opcode.isOneOf(Opcode.load, Opcode.store)
+}
+```
+
+```scala mdoc:invisible
+// Always need to run Chisel to see if there are elaboration errors
+ChiselStage.emitVerilog(new LoadStoreExample)
+```
+
 Some additional useful methods defined on the `ChiselEnum` object are:
 
 * `.all`: returns the enum values within the enumeration

src/test/scala/chiselTests/StrongEnum.scala

@@ -304,6 +304,41 @@ class StrongEnumFSMTester extends BasicTester {
   }
 }
 
+class IsOneOfTester extends BasicTester {
+  import EnumExample._
+
+  // is one of itself
+  assert(e0.isOneOf(e0))
+
+  // is one of Seq of itself
+  assert(e0.isOneOf(Seq(e0)))
+  assert(e0.isOneOf(Seq(e0, e0, e0, e0)))
+  assert(e0.isOneOf(e0, e0, e0, e0))
+
+  // is one of Seq of multiple elements
+  val subset = Seq(e0, e1, e2)
+  assert(e0.isOneOf(subset))
+  assert(e1.isOneOf(subset))
+  assert(e2.isOneOf(subset))
+
+  // is not element not in subset
+  assert(!e100.isOneOf(subset))
+  assert(!e101.isOneOf(subset))
+
+  // test multiple elements with variable number of arguments
+  assert(e0.isOneOf(e0, e1, e2))
+  assert(e1.isOneOf(e0, e1, e2))
+  assert(e2.isOneOf(e0, e1, e2))
+  assert(!e100.isOneOf(e0, e1, e2))
+  assert(!e101.isOneOf(e0, e1, e2))
+
+  // is not another value
+  assert(!e0.isOneOf(e1))
+  assert(!e2.isOneOf(e101))
+
+  stop()
+}
+
 class StrongEnumSpec extends ChiselFlatSpec with Utils {
   import chisel3.internal.ChiselException
 
@@ -474,6 +509,10 @@ class StrongEnumSpec extends ChiselFlatSpec with Utils {
     val (log, _) = grabLog(ChiselStage.elaborate(new MyModule))
     log should not include ("warn")
   }
+
+  it should "correctly check if the enumeration is one of the values in a given sequence" in {
+    assertTesterPasses(new IsOneOfTester)
+  }
 }
 
 class StrongEnumAnnotator extends Module {