From 741132ce955e5f1d7e545119ed5d709097e9ad01 Mon Sep 17 00:00:00 2001
From: Jamie Willis <j.willis19@imperial.ac.uk>
Date: Mon, 29 Apr 2024 13:35:11 +0100
Subject: [PATCH] removed redundant handler in chainr1 implementation

---
 .../backend/IterativeEmbedding.scala          | 10 +++-------
 .../machine/instructions/CoreInstrs.scala     |  4 ++--
 .../instructions/IterativeInstrs.scala        | 20 +++++++------------
 3 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/parsley/shared/src/main/scala/parsley/internal/deepembedding/backend/IterativeEmbedding.scala b/parsley/shared/src/main/scala/parsley/internal/deepembedding/backend/IterativeEmbedding.scala
index 6103f0c47..db3485621 100644
--- a/parsley/shared/src/main/scala/parsley/internal/deepembedding/backend/IterativeEmbedding.scala
+++ b/parsley/shared/src/main/scala/parsley/internal/deepembedding/backend/IterativeEmbedding.scala
@@ -115,19 +115,15 @@ private [deepembedding] final class Chainr[A, B](p: StrictParsley[A], op: Strict
     override def codeGen[M[_, +_]: ContOps, R](producesResults: Boolean)(implicit instrs: InstrBuffer, state: CodeGenState): M[R, Unit]= {
         if (producesResults) {
             val body = state.freshLabel()
-            // handler1 is where the check offset is kept
-            val handler1 = state.getLabel(instructions.Refail)
-            val handler2 = state.freshLabel()
+            val handler = state.freshLabel()
             instrs += new instructions.Push(identity[Any] _)
-            instrs += new instructions.PushHandler(handler1)
             instrs += new instructions.Label(body)
             suspend(p.codeGen[M, R](producesResults=true)) >> {
-                instrs += new instructions.PushHandler(handler2)
+                instrs += new instructions.PushHandler(handler)
                 suspend(op.codeGen[M, R](producesResults=true)) |> {
                     instrs += new instructions.ChainrJump(body)
-                    instrs += new instructions.Label(handler2)
+                    instrs += new instructions.Label(handler)
                     instrs += instructions.ChainrOpHandler(wrap)
-                    if (!producesResults) instrs += instructions.Pop
                 }
             }
         }
diff --git a/parsley/shared/src/main/scala/parsley/internal/machine/instructions/CoreInstrs.scala b/parsley/shared/src/main/scala/parsley/internal/machine/instructions/CoreInstrs.scala
index 028f2f3f8..192c68afa 100644
--- a/parsley/shared/src/main/scala/parsley/internal/machine/instructions/CoreInstrs.scala
+++ b/parsley/shared/src/main/scala/parsley/internal/machine/instructions/CoreInstrs.scala
@@ -279,7 +279,7 @@ private [internal] final class RestoreAndPushHandler(var label: Int) extends Ins
     // $COVERAGE-ON$
 }
 
-private [internal] object Refail extends Instr {
+/*private [internal] object Refail extends Instr {
     override def apply(ctx: Context): Unit = {
         ensureHandlerInstruction(ctx)
         ctx.handlers = ctx.handlers.tail
@@ -289,4 +289,4 @@ private [internal] object Refail extends Instr {
     // $COVERAGE-OFF$
     override def toString: String = "Refail"
     // $COVERAGE-ON$
-}
+}*/
diff --git a/parsley/shared/src/main/scala/parsley/internal/machine/instructions/IterativeInstrs.scala b/parsley/shared/src/main/scala/parsley/internal/machine/instructions/IterativeInstrs.scala
index 0ff124727..412ef10c2 100644
--- a/parsley/shared/src/main/scala/parsley/internal/machine/instructions/IterativeInstrs.scala
+++ b/parsley/shared/src/main/scala/parsley/internal/machine/instructions/IterativeInstrs.scala
@@ -111,14 +111,6 @@ private [internal] final class Chainl(var label: Int) extends InstrWithLabel {
     // $COVERAGE-ON$
 }
 
-private [instructions] object DualHandler {
-    def popSecondHandlerAndJump(ctx: Context, label: Int): Unit = {
-        ctx.handlers = ctx.handlers.tail
-        ctx.updateCheckOffset()
-        ctx.pc = label
-    }
-}
-
 private [internal] final class ChainrJump(var label: Int) extends InstrWithLabel {
     override def apply(ctx: Context): Unit = {
         ensureRegularInstruction(ctx)
@@ -127,7 +119,8 @@ private [internal] final class ChainrJump(var label: Int) extends InstrWithLabel
         val acc = ctx.stack.peek[Any => Any]
         // We perform the acc after the tos function; the tos function is "closer" to the final p
         ctx.stack.exchange((y: Any) => acc(f(x, y)))
-        DualHandler.popSecondHandlerAndJump(ctx, label)
+        ctx.handlers = ctx.handlers.tail
+        ctx.pc = label
     }
 
     // $COVERAGE-OFF$
@@ -138,9 +131,7 @@ private [internal] final class ChainrJump(var label: Int) extends InstrWithLabel
 private [internal] final class ChainrOpHandler(wrap: Any => Any) extends Instr {
     override def apply(ctx: Context): Unit = {
         ensureHandlerInstruction(ctx)
-        val check = ctx.handlers.check
-        ctx.handlers = ctx.handlers.tail
-        ctx.catchNoConsumed(check) {
+        ctx.catchNoConsumed(ctx.handlers.check) {
             ctx.handlers = ctx.handlers.tail
             ctx.addErrorToHintsAndPop()
             val y = ctx.stack.upop()
@@ -163,7 +154,10 @@ private [internal] final class SepEndBy1Jump(var label: Int) extends InstrWithLa
         ctx.stack.pop_() // the bool
         ctx.stack.peek[mutable.Builder[Any, Any]] += x
         ctx.stack.upush(true)
-        DualHandler.popSecondHandlerAndJump(ctx, label)
+        // pop second handler and jump
+        ctx.handlers = ctx.handlers.tail
+        ctx.updateCheckOffset()
+        ctx.pc = label
     }
 
     // $COVERAGE-OFF$