optimize: flip if true/else blocks if the else block only contains a jump (inverting the condition)

codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt

@@ -110,6 +110,22 @@ class StatementOptimizer(private val program: Program,
                 IAstModification.InsertAfter(ifElse, elsePart, parent as IStatementContainer)
             )
         }
+
+        // switch if/else around if the else is just a jump or branch
+        if(ifElse.elsepart.isNotEmpty() && ifElse.elsepart.statements.size==1) {
+            val jump = ifElse.elsepart.statements[0]
+            if(jump is Jump) {
+                val newTruePart = AnonymousScope(mutableListOf(jump), ifElse.elsepart.position)
+                val newElsePart = AnonymousScope(ifElse.truepart.statements, ifElse.truepart.position)
+                val invertedCondition = PrefixExpression("not", ifElse.condition, ifElse.condition.position)
+                return listOf(
+                    IAstModification.ReplaceNode(ifElse.elsepart, newElsePart, ifElse),
+                    IAstModification.ReplaceNode(ifElse.truepart, newTruePart, ifElse),
+                    IAstModification.ReplaceNode(ifElse.condition, invertedCondition, ifElse)
+                )
+            }
+        }
+
         return noModifications
     }
 
@@ -460,7 +476,7 @@ class StatementOptimizer(private val program: Program,
         if(whenStmt.condition.inferType(program).isBool) {
             if(whenStmt.choices.all { it.values?.size==1 }) {
                 if (whenStmt.choices.all { it.values!!.single().constValue(program)!!.number in arrayOf(0.0, 1.0) }) {
-                    // it's a when statement on booleans that can just be replaced by an if or if..else.
+                    // it's a when statement on booleans that can just be replaced by an if or if-else.
                     if (whenStmt.choices.size == 1) {
                         return if(whenStmt.choices[0].values!![0].constValue(program)!!.number==1.0) {
                             replaceWithIf(whenStmt.condition, whenStmt.choices[0].statements, null)

compiler/src/prog8/compiler/Compiler.kt

@@ -112,9 +112,11 @@ fun compileProgram(args: CompilerArguments): CompilationResult? {
                 program.processAstBeforeAsmGeneration(compilationOptions, args.errors)
                 args.errors.report()
 
-                val intermediateAst = IntermediateAstMaker(program, args.errors).transform()
 //                println("*********** COMPILER AST RIGHT BEFORE ASM GENERATION *************")
 //                printProgram(program)
+
+                val intermediateAst = IntermediateAstMaker(program, args.errors).transform()
+
 //                println("*********** AST RIGHT BEFORE ASM GENERATION *************")
 //                printAst(intermediateAst, true, ::println)
 

compiler/src/prog8/compiler/astprocessing/BoolRemover.kt

@@ -95,6 +95,16 @@ internal class BoolRemover(val program: Program) : AstWalker() {
         }
         return noModifications
     }
+
+    override fun after(expr: PrefixExpression, parent: Node): Iterable<IAstModification> {
+        if(expr.operator=="not") {
+            val exprDt = expr.expression.inferType(program).getOrElse { throw FatalAstException("unknown dt") }
+            val nonBoolDt = if(exprDt==DataType.BOOL) DataType.UBYTE else exprDt
+            val equalZero = BinaryExpression(expr.expression, "==", NumericLiteral(nonBoolDt, 0.0, expr.expression.position), expr.expression.position)
+            return listOf(IAstModification.ReplaceNode(expr, equalZero, parent))
+        }
+        return noModifications
+    }
 }
 
 internal fun wrapWithBooleanCastIfNeeded(expr: Expression, program: Program): Expression? {

docs/source/todo.rst

@@ -2,17 +2,15 @@
 TODO
 ====
 
-- optimize: flip if true/else blocks if the else block only contains a jump (invert condition!)
+- IR (expericodegen): fix code for calling routines that return a boolean in a status register such as Carry flag, it has to store the flag value somewhere
 
-- merge branch optimize-st  for some optimizations regardign SymbolTable use
+- merge branch optimize-st  for some optimizations regarding SymbolTable use
 
 - [on branch: call-pointers] allow calling a subroutine via a pointer variable (indirect JSR, optimized form of callfar())
    modify programs (shell, paint) that now use callfar
 
 - [on branch: shortcircuit] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
 
-- IR (expericodegen): fix code for calling routines that return a boolean in a status register such as Carry flag, it has to store the flag value somewhere
-
 ...
 
 

examples/test.p8

@@ -4,86 +4,23 @@
 
 main {
     sub start() {
-        ; expected output: 0000
+        if test_c_set()
-        cx16.r0L = test_c_clear()
+            txt.print("yes1\n")
-        cx16.r1L = test_z_clear()
-        cx16.r2L = test_n_clear()
-        cx16.r3L = test_v_clear()
-        txt.print_ub(cx16.r0L)
-        txt.print_ub(cx16.r1L)
-        txt.print_ub(cx16.r2L)
-        txt.print_ub(cx16.r3L)
-        txt.nl()
-        ; expected output: 1111
-        cx16.r0L = test_c_set()
-        cx16.r1L = test_z_set()
-        cx16.r2L = test_n_set()
-        cx16.r3L = test_v_set()
-        txt.print_ub(cx16.r0L)
-        txt.print_ub(cx16.r1L)
-        txt.print_ub(cx16.r2L)
-        txt.print_ub(cx16.r3L)
-        txt.nl()
-
-        ; exptected output: no2, no3,  no5, yes6, no7, yes8
-        if not test_c_clear()
-            goto skip1
         else
-            txt.print("no1\n")
+            goto skip1
+
+        txt.print("no1\n")
 
 skip1:
         if test_c_clear()
-            goto skip2
+            txt.print("yes2\n")
         else
-            txt.print("no2\n")
+            goto skip2
+
+        txt.print("no1\n")
 
 skip2:
-
+        txt.print("done\n")
-        if not test_c_set()
-            goto skip3
-        else
-            txt.print("no3\n")
-
-skip3:
-        if test_c_set()
-            goto skip4
-        else
-            txt.print("no4\n")
-
-skip4:
-
-        if test_c_clear() {
-            txt.print("yes5\n")
-            goto skip5
-        }
-        txt.print("no5\n")
-
-skip5:
-        if not test_c_clear() {
-            txt.print("yes6\n")
-            goto skip6
-        }
-        txt.print("no6\n")
-
-skip6:
-        if test_c_clear()
-            txt.print("yes7\n")
-        else
-            txt.print("no7\n")
-
-        if not test_c_clear()
-            txt.print("yes8\n")
-        else
-            txt.print("no8\n")
-
-
-        while test_c_clear() {
-            cx16.r0++
-        }
-
-        do {
-            cx16.r0++
-        } until test_c_set()
     }
 
     asmsub test_c_clear() -> bool @Pc {