From 7aec627f6b43f550c34ac947017edc5b7365dfe2 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sun, 8 Sep 2024 22:26:01 +0200
Subject: [PATCH] add optimization if x==0 or x==1 -> if x<2

---
 compiler/res/prog8lib/cx16/sprites.p8         |  2 +-
 .../compiler/astprocessing/VariousCleanups.kt | 18 ++++++++--
 docs/source/todo.rst                          |  3 --
 examples/test.p8                              | 36 ++++---------------
 4 files changed, 23 insertions(+), 36 deletions(-)

diff --git a/compiler/res/prog8lib/cx16/sprites.p8 b/compiler/res/prog8lib/cx16/sprites.p8
index d89f16b20..b85ae74ac 100644
--- a/compiler/res/prog8lib/cx16/sprites.p8
+++ b/compiler/res/prog8lib/cx16/sprites.p8
@@ -23,7 +23,7 @@ sprites {
              ubyte databank, uword dataaddr,
              ubyte width_flag, ubyte height_flag,
              ubyte colors_flag, ubyte palette_offset) {
-        hide(spritenum)
+        pos(spritenum, -64, -64)                    ; move sprite off-screen initially
         cx16.VERA_DC_VIDEO |= %01000000             ; enable sprites globally
         dataaddr >>= 5
         dataaddr |= (databank as uword)<<11
diff --git a/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt b/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
index abc545a6d..8eca2c019 100644
--- a/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
+++ b/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
@@ -135,9 +135,23 @@ internal class VariousCleanups(val program: Program, val errors: IErrorReporter,
                 }
 
                 if(isMultiComparisonRecurse(leftBinExpr1)) {
-                    // replace it!
-                    val valueCopies = values.sortedBy { it.number }.map { it.copy() }
                     val elementType = needle.inferType(program).getOrElse { throw FatalAstException("invalid needle dt") }
+                    if(values.size==2 || values.size==3 && elementType in IntegerDatatypes) {
+                        val numbers = values.map{it.number}.toSet()
+                        if(numbers == setOf(0.0, 1.0)) {
+                            // we can replace x==0 or x==1 with x<2
+                            val compare = BinaryExpression(needle, "<", NumericLiteral(elementType, 2.0, expr.position), expr.position)
+                            return listOf(IAstModification.ReplaceNode(expr, compare, parent))
+                        }
+                        if(numbers == setOf(0.0, 1.0, 2.0)) {
+                            // we can replace x==0 or x==1 or x==2 with x<3
+                            val compare = BinaryExpression(needle, "<", NumericLiteral(elementType, 3.0, expr.position), expr.position)
+                            return listOf(IAstModification.ReplaceNode(expr, compare, parent))
+                        }
+                    }
+                    if(values.size<4)
+                        return noModifications  // replacement only worthwhile for 4 or more values
+                    val valueCopies = values.sortedBy { it.number }.map { it.copy() }
                     val arrayType = ElementToArrayTypes.getValue(elementType)
                     val valuesArray = ArrayLiteral(InferredTypes.InferredType.known(arrayType), valueCopies.toTypedArray(), expr.position)
                     val containment = ContainmentCheck(needle, valuesArray, expr.position)
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index b44c9a529..181a4fc9c 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -1,9 +1,6 @@
 TODO
 ====
 
-Main branch: possible optimization for:  if x < 2/ x<1  ->  if x==0 or x==1   likewise for > 253/ >254
-
-
 Improve register load order in subroutine call args assignments:
 in certain situations, the "wrong" order of evaluation of function call arguments is done which results
 in overwriting registers that already got their value, which requires a lot of stack juggling (especially on plain 6502 cpu!)
diff --git a/examples/test.p8 b/examples/test.p8
index 6660a3ba2..55b0288f4 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,37 +4,13 @@
 
 main {
     sub start() {
-        ubyte @shared x
-        uword @shared w
+        byte @shared x
+        word @shared w
 
-        x=2
-        if x==2 or cx16.r0L==42
-            txt.print("yep0\n")
+        if x==0 or x==1 or x==2
+            x++
 
-        if x==1 or x==2
-            txt.print("yep1\n")
-
-        x = 9
-        if x==1 or x==2
-            txt.print("yep2-shouldn't-see-this\n")      ; TODO fix this in IR/VM
-
-        if x in 1 to 4
-            txt.print("yep3-shouldn't-see-this\n")
-        if x in 4 to 10
-            txt.print("yep4\n")
-
-
-        w=2222
-        if w==1111 or w==2222
-            txt.print("w-yep1\n")
-
-        w = 4999
-        if w==1111 or w==2222
-            txt.print("w-yep2-shouldn't-see-this\n")      ; TODO fix this in IR/VM
-
-        if w in 1111 to 4444
-            txt.print("w-yep3-shouldn't-see-this\n")
-        if w in 4444 to 5555
-            txt.print("w-yep4\n")
+        if w==0 or w==1 or w==2
+            x++
     }
 }