From 6af3209d4db81252729dbd891448b7351c5f8d34 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Wed, 17 Nov 2021 00:57:00 +0100
Subject: [PATCH] add more const foldings

---
 .../optimizer/ConstantFoldingOptimizer.kt     | 27 ++++++++++
 .../prog8/optimizer/ExpressionSimplifier.kt   |  6 ---
 docs/source/todo.rst                          |  5 +-
 examples/test.p8                              | 49 +++++++++++++------
 4 files changed, 66 insertions(+), 21 deletions(-)

diff --git a/codeOptimizers/src/prog8/optimizer/ConstantFoldingOptimizer.kt b/codeOptimizers/src/prog8/optimizer/ConstantFoldingOptimizer.kt
index b83aabc9d..16c06bb25 100644
--- a/codeOptimizers/src/prog8/optimizer/ConstantFoldingOptimizer.kt
+++ b/codeOptimizers/src/prog8/optimizer/ConstantFoldingOptimizer.kt
@@ -101,6 +101,33 @@ class ConstantFoldingOptimizer(private val program: Program) : AstWalker() {
         val rightconst = expr.right.constValue(program)
         val modifications = mutableListOf<IAstModification>()
 
+        if(expr.operator=="==" && rightconst!=null) {
+            val leftExpr = expr.left as? BinaryExpression
+            if(leftExpr!=null) {
+                val leftRightConst = leftExpr.right.constValue(program)
+                if(leftRightConst!=null) {
+                    when (leftExpr.operator) {
+                        "+" -> {
+                            // X + С1 == C2  -->  X == C2 - C1
+                            val newRightConst = NumericLiteralValue(rightconst.type, rightconst.number - leftRightConst.number, rightconst.position)
+                            return listOf(
+                                IAstModification.ReplaceNode(leftExpr, leftExpr.left, expr),
+                                IAstModification.ReplaceNode(expr.right, newRightConst, expr)
+                            )
+                        }
+                        "-" -> {
+                            // X - С1 == C2  -->  X == C2 + C1
+                            val newRightConst = NumericLiteralValue(rightconst.type, rightconst.number + leftRightConst.number, rightconst.position)
+                            return listOf(
+                                IAstModification.ReplaceNode(leftExpr, leftExpr.left, expr),
+                                IAstModification.ReplaceNode(expr.right, newRightConst, expr)
+                            )
+                        }
+                    }
+                }
+            }
+        }
+
         if(expr.operator == "**" && leftconst!=null) {
             // optimize various simple cases of ** :
             //  optimize away 1 ** x into just 1 and 0 ** x into just 0
diff --git a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
index 9577a4b7d..b924dc9b6 100644
--- a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
+++ b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
@@ -19,12 +19,6 @@ import kotlin.math.pow
 
     Investigate what optimizations binaryen has, also see  https://egorbo.com/peephole-optimizations.html
 
-Add some const foldings (that may already be done as well):
-X + С1 == C2  =>  X == C2 - C1
-((X + C1) + C2)  =>  (X + (C1 + C2))
-((X + C1) + (Y + C2))  =>  ((X + Y) + (C1 + C2))
-
-
  */
 
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 5b1485073..d48d34f67 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,7 +3,10 @@ TODO
 
 For next compiler release (7.4)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-...
+BUG: Fix C-64sound issue in petaxian (regression since 7.3, sound on c64 build works fine on older versions)
+BUG:    ubyte z1
+        ubyte z2
+        z2=z1+z2+5    CRASHES COMPILER
 
 
 Blocked by an official Commander-x16 v39 release
diff --git a/examples/test.p8 b/examples/test.p8
index 3590901c9..8ccdd4c83 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -13,22 +13,43 @@ main {
 
         ; TODO:  bitwise operations with a negative constant number -> replace the number by its positive 2 complement
 
-        if aw<1
-            yy++
-        if aw<=0
-            yy++
+; (X + C1) + (Y + C2)  =>  (X + Y) + (C1 + C2)
+; (X + C1) - (Y + C2)  =>  (X - Y) + (C1 - C2)
+; ---> together:   (X + C1) <plusmin> (Y + C2)  =>  (X <plusmin> Y) + (C1 <plusmin> C2)
 
-        if yy<1
-            yy++
-        if yy<=0
-            yy++
-        if bb<1
-            yy++
-        if bb<=0
-            yy++
 
-        txt.print_ub(yy)
-        txt.print_uw(aw)
+; (X - C1) + (Y - C2)  =>  (X + Y) - (C1 + C2)
+; (X - C1) - (Y - C2)  =>  (X - Y) - (C1 - C2)
 
+        xx=6
+        yy=8
+
+
+        yy = (xx+5)+(yy+10)
+        ; yy = (xx+yy)+(5+10)     ; TODO crashes compiler
+        txt.print_ub(yy)        ; 29
+        txt.nl()
+
+        xx=100
+        yy=8
+        ;yy = (xx+5)-(yy+10)
+        yy = (xx-yy)+(5-10) as ubyte
+        txt.print_ub(yy)        ; 87
+        txt.nl()
+
+        xx=50
+        yy=40
+        yy = (xx-5)+(yy-10)
+        txt.print_ub(yy)        ; 75
+        txt.nl()
+
+        xx=50
+        yy=20
+        yy = (xx-5)-(yy-10)
+        txt.print_ub(yy)        ; 35
+        txt.nl()
+
+        repeat {
+        }
     }
 }