Optimize period equality tests

Author: odersky

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

@@ -20,7 +20,7 @@ object Periods {
   /** Are all base types in the current period guaranteed to be the same as in period `p`? */
   def currentHasSameBaseTypesAs(p: Period)(using Context): Boolean =
     val period = ctx.period
-    period == p ||
+    period.code == p.code ||
     period.runId == p.runId &&
       unfusedPhases(period.phaseId).sameBaseTypesStartId ==
       unfusedPhases(p.phaseId).sameBaseTypesStartId

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

@@ -2867,7 +2867,7 @@ object SymDenotations {
     }
 
     def isValidAt(phase: Phase)(using Context) =
-      checkedPeriod == ctx.period ||
+      checkedPeriod.code == ctx.period.code ||
         createdAt.runId == ctx.runId &&
         createdAt.phaseId < unfusedPhases.length &&
         sameGroup(unfusedPhases(createdAt.phaseId), phase) &&

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

@@ -103,7 +103,7 @@ object Symbols {
     /** The current denotation of this symbol */
     final def denot(using Context): SymDenotation = {
       util.Stats.record("Symbol.denot")
-      if (checkedPeriod == ctx.period) lastDenot
+      if checkedPeriod.code == ctx.period.code then lastDenot
       else computeDenot(lastDenot)
     }
 

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

@@ -2266,7 +2266,7 @@ object Types {
     final def symbol(using Context): Symbol =
       // We can rely on checkedPeriod (unlike in the definition of `denot` below)
       // because SymDenotation#installAfter never changes the symbol
-      if (checkedPeriod == ctx.period) lastSymbol.asInstanceOf[Symbol]
+      if (checkedPeriod.code == ctx.period.code) lastSymbol.asInstanceOf[Symbol]
       else computeSymbol
 
     private def computeSymbol(using Context): Symbol =