From 07c29fe8bf7e96bcace390bbe177aface736416c Mon Sep 17 00:00:00 2001
From: Jack Koenig <koenig@sifive.com>
Date: Wed, 12 Jan 2022 10:52:20 -0800
Subject: [PATCH 1/2] Support using Treadle for 'sbt test'

Treadle will be used as the "defaultBackend" when the environment
variable CHISEL3_CI_USE_TREADLE is set. The intent is to set this
variable during CI for pre-merge CI (aka on pull requests).

(cherry picked from commit 7d39b7bd2b6f38dac90fe25064744ffc0ada0fe4)
---
 .github/workflows/test.yml                  | 2 +-
 src/test/scala/chiselTests/ChiselSpec.scala | 5 ++++-
 src/test/scala/chiselTests/Vec.scala        | 4 ++--
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9ace173eec4..5469e1e0e2c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -51,7 +51,7 @@ jobs:
         if: startsWith(matrix.scala, '2.12')
         run: sbt ++${{ matrix.scala }} docs/mdoc unidoc
       - name: Test
-        run: sbt ++${{ matrix.scala }} test
+        run: sbt ++${{ matrix.scala }} "testOnly * -- -oD"
       - name: Binary compatibility
         run: sbt ++${{ matrix.scala }} mimaReportBinaryIssues
 
diff --git a/src/test/scala/chiselTests/ChiselSpec.scala b/src/test/scala/chiselTests/ChiselSpec.scala
index 6f560b94ff1..e00afcf6df1 100644
--- a/src/test/scala/chiselTests/ChiselSpec.scala
+++ b/src/test/scala/chiselTests/ChiselSpec.scala
@@ -38,7 +38,10 @@ trait ChiselRunners extends Assertions with BackendCompilationUtilities {
     annotations:          AnnotationSeq = Seq()
   ): Boolean = {
     // Change this to enable Treadle as a backend
-    val defaultBackend = chisel3.testers.TesterDriver.defaultBackend
+    val defaultBackend = {
+      val useTreadle = sys.env.get("CHISEL3_CI_USE_TREADLE").isDefined
+      if (useTreadle) chisel3.testers.TreadleBackend else chisel3.testers.TesterDriver.defaultBackend
+    }
     val hasBackend = TestUtils.containsBackend(annotations)
     val annos: Seq[Annotation] = if (hasBackend) annotations else defaultBackend +: annotations
     TesterDriver.execute(() => t, additionalVResources, annos)
diff --git a/src/test/scala/chiselTests/Vec.scala b/src/test/scala/chiselTests/Vec.scala
index 02743187127..4a871890f83 100644
--- a/src/test/scala/chiselTests/Vec.scala
+++ b/src/test/scala/chiselTests/Vec.scala
@@ -6,7 +6,7 @@ import org.scalacheck._
 
 import chisel3._
 import chisel3.stage.ChiselStage
-import chisel3.testers.BasicTester
+import chisel3.testers.{BasicTester, TesterDriver}
 import chisel3.util._
 import org.scalacheck.Shrink
 import scala.annotation.tailrec
@@ -456,7 +456,7 @@ class VecSpec extends ChiselPropSpec with Utils {
   }
 
   property("Infering widths on huge Vecs should not cause a stack overflow") {
-    assertTesterPasses { new HugeVecTester(10000) }
+    assertTesterPasses(new HugeVecTester(10000), annotations = TesterDriver.verilatorOnly)
   }
 
   property("A Reg of a Vec of a single 1 bit element should compile and work") {

From 43aadb4657932cdfc6e49463f28f07f78a10476e Mon Sep 17 00:00:00 2001
From: Jack Koenig <koenig@sifive.com>
Date: Tue, 27 Sep 2022 11:31:46 -0700
Subject: [PATCH 2/2] Use Treadle for CI on pull requests

(cherry picked from commit 82660673e56a816e68fcc068e3e04e127f076faf)
---
 .github/workflows/test.yml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5469e1e0e2c..139d59081b8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -50,8 +50,11 @@ jobs:
       - name: Documentation (Scala 2.12 only)
         if: startsWith(matrix.scala, '2.12')
         run: sbt ++${{ matrix.scala }} docs/mdoc unidoc
+      - name: Use Treadle for Pull Requests
+        if: github.event_name == 'pull_request'
+        run: echo "CHISEL3_CI_USE_TREADLE=1" >> $GITHUB_ENV
       - name: Test
-        run: sbt ++${{ matrix.scala }} "testOnly * -- -oD"
+        run: sbt ++${{ matrix.scala }} test
       - name: Binary compatibility
         run: sbt ++${{ matrix.scala }} mimaReportBinaryIssues