[targetutils] Add Chisel-side API for labelling the reset condition

sim/midas/targetutils/src/main/scala/midas/InstrumentationPredication.scala

@@ -0,0 +1,72 @@
+// See LICENSE for license details.
+
+package midas.targetutils
+
+import chisel3.dontTouch
+import chisel3.experimental.{ChiselAnnotation, annotate}
+
+import firrtl.annotations._
+import firrtl.transforms.DontTouchAllTargets
+
+/**
+  * Masks off assertions, printfs, and autocounter events when the target bool is deasserted. 
+  *
+  * Users typically wish to disable many forms instrumentation (e.g.,
+  * synthesized assertions and printfs, autocounters) while the target is
+  * under reset. By default, most of FireSim's instrumentations features mask
+  * off events using a module-local reset, generally Chisel's implicit reset.
+  * However, in some cases the module-local reset may not be asserted at the start of a
+  * reset sequence, leading to spurious assertion fires. This annotation
+  * provides a coarse-grained means to globally mask off these events until the
+  * target is sufficiently far in reset.
+  *
+  * Note, while it is possible to use this signal as a replacement for
+  * FireSim's trigger system, it is intended to support this time-zero reset
+  * case, and has different timing semantics.
+  * See: https://docs.fires.im/en/latest/Golden-Gate/Triggers.html
+  *
+  * @param target The boolean enable
+  *
+  */
+
+case class GlobalResetCondition(target: ReferenceTarget) extends
+    SingleTargetAnnotation[ReferenceTarget] with DontTouchAllTargets {
+  def duplicate(n: ReferenceTarget) = this.copy(target = n)
+}
+
+/**
+  * Indicates that this boolean target should be driven by the
+  * globalResetCondition if it is available.
+  */
+case class GlobalResetConditionSink(target: ReferenceTarget) extends
+    SingleTargetAnnotation[ReferenceTarget] with DontTouchAllTargets {
+  def duplicate(n: ReferenceTarget) = this.copy(target = n)
+}
+
+object GlobalResetCondition {
+  /**
+    * Label a bool as the global reset condition.
+    *
+    * @param target The chisel Bool to be annotated.
+    */
+  def apply(target: chisel3.Bool): Unit = {
+    // Workaround: Prevent promote passthroughs from extracting the fanout
+    // generated by wiring the GlobalResetCondition to sink bridges, by
+    // introducing an identity logic function that it cannot "see" through.
+    //
+    // If we neglect this, the wiring pass may introduce combinational
+    // dependency between channels in two different domains, which currently is
+    // not checked for and will produce simulator deadlock.
+    val condition = PassthroughBlocker(target)
+    annotate(new ChiselAnnotation { def toFirrtl = GlobalResetCondition(condition.toTarget) })
+  }
+
+  /**
+    * Label a bool that should be driven by the global reset condition.
+    *
+    * @param target The chisel Bool to be annotated.
+    */
+  def sink(target: chisel3.Bool): Unit = annotate(new ChiselAnnotation {
+    def toFirrtl = GlobalResetConditionSink(target.toTarget)
+  })
+}