Refactor TruthTable.apply and add factory method for Espresso (backport #2612) (#2620)

* Refactor TruthTable.apply and add factory method for Espresso (#2612)

Improves performance of creating TruthTables by processing entire BitPats
rather than individual bits. New TruthTable factory method enables
constructing TruthTables with semantics of OR-ing output BitPats together
rather than erroring when multiple terms have the same input BitPat.
This alternative factory method matches semantics for the output format
of Espresso.

Co-authored-by: Megan Wachs <megan@sifive.com>
Co-authored-by: Jack Koenig <koenig@sifive.com>
(cherry picked from commit 231f14e74f112a9f721e774561126b2bd1250039)

# Conflicts:
#	src/main/scala/chisel3/util/BitPat.scala

* Resolve backport conflicts

Co-authored-by: Aditya Naik <91489422+adkian-sifive@users.noreply.github.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/main/scala/chisel3/util/BitPat.scala b/src/main/scala/chisel3/util/BitPat.scala
index 33dd5b2b..7cb80e54 100644
--- a/src/main/scala/chisel3/util/BitPat.scala
+++ b/src/main/scala/chisel3/util/BitPat.scala
@@ -5,6 +5,8 @@ package chisel3.util
 import scala.language.experimental.macros
 import chisel3._
 import chisel3.internal.sourceinfo.{SourceInfo, SourceInfoTransform}
+import scala.collection.mutable
+import scala.util.hashing.MurmurHash3
 
 object BitPat {
 
@@ -253,6 +255,9 @@ sealed class BitPat(val value: BigInt, val mask: BigInt, val width: Int)
   def =/=(that: UInt):   Bool = macro SourceInfoTransform.thatArg
   def ##(that:  BitPat): BitPat = macro SourceInfoTransform.thatArg
 
+  override def hashCode: Int =
+    MurmurHash3.seqHash(Seq(this.value, this.mask, this.width))
+
   /** @group SourceInfoTransformMacro */
   def do_apply(x: Int)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): BitPat = {
     do_apply(x, x)