Perf?

Author: SolalPirelli

compiler/src/dotty/tools/backend/jvm/CoreBTypesFromSymbols.scala

@@ -211,7 +211,7 @@ final class CoreBTypesFromSymbols(val ppa: PostProcessorFrontendAccess)(using va
         if (innerClassSym.isAnonymousClass || innerClassSym.isAnonymousFunction) None
         else {
           val original = innerClassSym.initial
-          Some(atPhase(original.validFor.firstPhaseId)(innerClassSym.name).mangledString) // moduleSuffix for module classes
+          Some(atPhase(original.validFor.lastPhaseId)(innerClassSym.name).mangledString) // moduleSuffix for module classes
         }
       }
 

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -80,7 +80,7 @@ object DottyBackendInterface {
           // for example by specialization
           val original = toDenot(sym).initial
           val validity = original.validFor
-          atPhase(validity.firstPhaseId) {
+          atPhase(validity.lastPhaseId) {
             toDenot(sym).isStatic
           }
         }
@@ -90,7 +90,7 @@ object DottyBackendInterface {
         // it is very tricky in presence of classes(and anonymous classes) defined inside supper calls.
         if (sym.exists) {
           val validity = toDenot(sym).initial.validFor
-          atPhase(validity.firstPhaseId) {
+          atPhase(validity.lastPhaseId) {
             toDenot(sym).lexicallyEnclosingClass
           }
         } else NoSymbol

compiler/src/dotty/tools/dotc/core/Periods.scala

@@ -32,11 +32,12 @@ object Periods {
   /** A period is a contiguous sequence of phase ids in some run.
    *  It is coded as follows:
    *
-   *     sign, always 0:  1 bit
-   *     run id:          17 bits
-   *     last phase id:   7 bits
-   *     first phase id:  7 bits
+   *     sign, always 0:      1 bit
+   *     run id:              17 bits
+   *     last phase id:       7 bits
+   *     #phases before last: 7 bits
    *
+   *  This encoding ensures the < and > operators can be delegated as-is to `code`, making them cheap.
    */
   class Period private[Periods] (private val code: Int) extends AnyVal with Showable {
 
@@ -47,7 +48,7 @@ object Periods {
     def lastPhaseId: PhaseId = (code >>> PhaseWidth) & PhaseMask
 
     /** The first phase of this period */
-    def firstPhaseId: PhaseId = code & PhaseMask
+    def firstPhaseId: PhaseId = lastPhaseId - (code & PhaseMask)
 
     def containsPhaseId(id: PhaseId): Boolean = firstPhaseId <= id && id <= lastPhaseId
 
@@ -80,10 +81,10 @@ object Periods {
           this.lastPhaseId max that.lastPhaseId)
 
     inline def <(that: Period): Boolean =
-      this.runId < that.runId || (this.runId == that.runId && this.lastPhaseId < that.firstPhaseId)
+      this.code < that.code
 
     inline def >(that: Period): Boolean =
-      this.runId > that.runId || (this.runId == that.runId && this.firstPhaseId > that.lastPhaseId)
+      this.code > that.code
 
     def toText(p: Printer): Text =
       inContext(p.printerContext):
@@ -113,11 +114,11 @@ object Periods {
 
     /** The single-phase period consisting of given run id and phase id */
     def apply(rid: RunId, pid: PhaseId): Period =
-      new Period((((rid << PhaseWidth) | pid) << PhaseWidth) | pid)
+      new Period(((rid << PhaseWidth) | pid) << PhaseWidth)
 
     /** The period consisting of given run id, and lo/hi phase ids */
     def apply(rid: RunId, loPid: PhaseId, hiPid: PhaseId): Period =
-      new Period((((rid << PhaseWidth) | hiPid) << PhaseWidth) | loPid)
+      new Period((((rid << PhaseWidth) | hiPid) << PhaseWidth) | (hiPid - loPid))
 
     /** The interval consisting of all periods of given run id */
     def allInRun(rid: RunId): Period =

compiler/src/dotty/tools/dotc/core/Phases.scala

@@ -49,7 +49,7 @@ object Phases {
 
     def recordRecheckPhase(phase: Recheck): Unit =
       val id = phase.id
-      assert(id < 64, s"Recheck phase with id $id outside permissible range 0..63")
+      assert(id < 64, s"Recheck phase with id $id outside range 0..63, cannot use Long bits encoding")
       myRecheckPhaseIds |= (1L << id)
 
     object SomePhase extends Phase {