From fee58e98c5811aeabd789474ac4822043683bd88 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sun, 3 Jul 2022 12:50:39 +0200
Subject: [PATCH] tiny optimization

---
 .../astprocessing/BeforeAsmAstChanger.kt      | 35 +++++++++++++++++--
 docs/source/todo.rst                          | 18 ++++++++--
 2 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt b/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
index 3fc37769d..8f7708306 100644
--- a/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
+++ b/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
@@ -67,6 +67,10 @@ internal class BeforeAsmAstChanger(val program: Program,
         // Try to replace A = B <operator> Something  by A= B, A = A <operator> Something
         // this triggers the more efficent augmented assignment code generation more often.
         // But it can only be done if the target variable IS NOT OCCURRING AS AN OPERAND ITSELF.
+
+        if(options.compTarget.name==VMTarget.NAME)   // don't apply this optimization for Vm target
+            return noModifications
+
         if(!assignment.isAugmentable
             && assignment.target.identifier != null
             && !assignment.target.isIOAddress(options.compTarget.machine)) {
@@ -170,8 +174,35 @@ internal class BeforeAsmAstChanger(val program: Program,
 
     override fun after(ifElse: IfElse, parent: Node): Iterable<IAstModification> {
         val binExpr = ifElse.condition as? BinaryExpression
-        if(binExpr==null || binExpr.operator !in ComparisonOperators) {
-            // if x  ->  if x!=0,    if x+5  ->  if x+5 != 0
+        if(binExpr==null) {
+            // if x  ->  if x!=0
+            val booleanExpr = BinaryExpression(
+                ifElse.condition,
+                "!=",
+                NumericLiteral.optimalInteger(0, ifElse.condition.position),
+                ifElse.condition.position
+            )
+            return listOf(IAstModification.ReplaceNode(ifElse.condition, booleanExpr, ifElse))
+        }
+
+        if(binExpr.operator !in ComparisonOperators) {
+            val constRight = binExpr.right.constValue(program)
+            if(constRight!=null) {
+                if (binExpr.operator == "+") {
+                    // if x+5  ->  if x != -5
+                    val number = NumericLiteral(constRight.type, -constRight.number, constRight.position)
+                    val booleanExpr = BinaryExpression(binExpr.left,"!=", number, ifElse.condition.position)
+                    return listOf(IAstModification.ReplaceNode(ifElse.condition, booleanExpr, ifElse))
+                }
+                else if (binExpr.operator == "-") {
+                    // if x-5  ->  if x != 5
+                    val number = NumericLiteral(constRight.type, constRight.number, constRight.position)
+                    val booleanExpr = BinaryExpression(binExpr.left,"!=", number, ifElse.condition.position)
+                    return listOf(IAstModification.ReplaceNode(ifElse.condition, booleanExpr, ifElse))
+                }
+            }
+
+            // if x*5  ->  if x*5 != 0
             val booleanExpr = BinaryExpression(
                 ifElse.condition,
                 "!=",
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 134a7d9f1..32c2503fa 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,7 +3,7 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-...
+- bool data type? see below
 
 
 Need help with
@@ -16,7 +16,6 @@ Need help with
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
 Compiler:
-- add true 'bool' type that can only be 0 or 1, so that logical expressons don't have to use boolean() all the time on their operands
 - add some more optimizations in vmPeepholeOptimizer
 - vm Instruction needs to know what the read-registers/memory are, and what the write-register/memory is.
   this info is needed for more advanced optimizations and later code generation steps.
@@ -80,6 +79,21 @@ Optimizations:
 - when a for loop's loopvariable isn't referenced in the body, and the iterations are known, replace the loop by a repeatloop
   but we have no efficient way right now to see if the body references a variable.
 
+BOOL data type?
+---------------
+Logical expressions now need to sprinkle boolean() calls on their operands to yield the correct boolean 0 or 1 result.
+This is inefficient because most of the time the operands already are boolean but the compiler doesn't know this
+because the type of boolean values is UBYTE (so theoretically the value can be anything from 0 - 255)
+
+So the idea is to add a true 'bool' type
+
+- add BOOL datatype
+- add ARRAY_OF_BOOL array type
+- assignments to it automatically do boolean() conversion
+- logical expressions don't wrap operand of this type
+- bool & 1 -> bool
+- before codegen, bool type is discarded and it's just UBYTE
+
 
 STRUCTS again?
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