optimize calls/jumps and loops with always known conditions.

compiler/examples/cube3d.p8

@@ -30,21 +30,21 @@
     float[len(zcoor)] rotatedz
 
     sub start()  {
-        if irq.time_changed {
-            irq.time_changed = 0
-            _vm_gfx_clearscr(0)
-            _vm_gfx_text(8, 6, 1, "Spin")
-            _vm_gfx_text(29, 11, 1, "to Win !")
+        while(1) {
+            if irq.time_changed {
+                irq.time_changed = 0
+                _vm_gfx_clearscr(0)
+                _vm_gfx_text(8, 6, 1, "Spin")
+                _vm_gfx_text(29, 11, 1, "to Win !")
 
-            for byte i in 0 to width//10 {
-                _vm_gfx_line(i*2+width//2-width//10, 130, i*10.w, 199, 6)
+                for byte i in 0 to width//10 {
+                    _vm_gfx_line(i*2+width//2-width//10, 130, i*10.w, 199, 6)
+                }
+
+                rotate_vertices(flt(irq.global_time) / 30.0)
+                draw_edges()
             }
-
-            rotate_vertices(flt(irq.global_time) / 30.0)
-            draw_edges()
-
         }
-        goto start
     }
 
     sub rotate_vertices(t: float) {

compiler/examples/test.p8

@@ -4,12 +4,17 @@
 
 ~ main {
 
-    byte[10,5] barray = 0
-
 sub start() {
-    X=barray[2,3]
-    barray[3,3]=X
 
+    repeat {
+        _vm_write_str("333\n")
+    } until(1)
+
+    repeat {
+        _vm_write_str("444\n")
+    } until (0)
+
+    return
 
 }
 

compiler/src/prog8/ast/AST.kt

@@ -307,12 +307,12 @@ interface INameScope {
                 is WhileLoop -> subscopes[stmt.body.name] = stmt.body
                 is BranchStatement -> {
                     subscopes[stmt.truepart.name] = stmt.truepart
-                    if(!stmt.elsepart.isEmpty())
+                    if(stmt.elsepart.isNotEmpty())
                         subscopes[stmt.elsepart.name] = stmt.elsepart
                 }
                 is IfStatement -> {
                     subscopes[stmt.truepart.name] = stmt.truepart
-                    if(!stmt.elsepart.isEmpty())
+                    if(stmt.elsepart.isNotEmpty())
                         subscopes[stmt.elsepart.name] = stmt.elsepart
                 }
             }
@@ -368,6 +368,13 @@ interface INameScope {
     }
 
     fun isEmpty() = statements.isEmpty()
+    fun isNotEmpty() = statements.isNotEmpty()
+
+    fun remove(stmt: IStatement) {
+        val removed = statements.remove(stmt)
+        if(!removed)
+            throw FatalAstException("stmt to remove wasn't found in scope")
+    }
 }
 
 
@@ -1153,7 +1160,7 @@ class PostIncrDecr(var target: AssignTarget, val operator: String, override val
 
 class Jump(val address: Int?,
            val identifier: IdentifierReference?,
-           val generatedLabel: String?,
+           val generatedLabel: String?,             // used in code generation scenarios
            override val position: Position) : IStatement {
     override lateinit var parent: Node
 

compiler/src/prog8/ast/AstChecker.kt

@@ -83,7 +83,13 @@ class AstChecker(private val namespace: INameScope,
     override fun process(returnStmt: Return): IStatement {
         val expectedReturnValues = (returnStmt.definingScope() as? Subroutine)?.returnvalues ?: emptyList()
         if(expectedReturnValues.size != returnStmt.values.size) {
-            checkResult.add(SyntaxError("number of return values doesn't match subroutine return spec", returnStmt.position))
+            // if the return value is a function call, check the result of that call instead
+            if(returnStmt.values.size==1 && returnStmt.values[0] is FunctionCall) {
+                val dt = (returnStmt.values[0] as FunctionCall).resultingDatatype(namespace, heap)
+                if(dt!=null && expectedReturnValues.isEmpty())
+                    checkResult.add(SyntaxError("number of return values doesn't match subroutine return spec", returnStmt.position))
+            } else
+                checkResult.add(SyntaxError("number of return values doesn't match subroutine return spec", returnStmt.position))
         }
 
         for (rv in expectedReturnValues.withIndex().zip(returnStmt.values)) {
@@ -176,8 +182,8 @@ class AstChecker(private val namespace: INameScope,
 
     override fun process(label: Label): IStatement {
         // scope check
-        if(label.parent !is Block && label.parent !is Subroutine) {
-            checkResult.add(SyntaxError("Labels can only be defined in the scope of a block or within another subroutine", label.position))
+        if(label.parent !is Block && label.parent !is Subroutine && label.parent !is AnonymousScope) {
+            checkResult.add(SyntaxError("Labels can only be defined in the scope of a block, a loop body, or within another subroutine", label.position))
         }
         return super.process(label)
     }

compiler/src/prog8/compiler/Compiler.kt

@@ -135,9 +135,16 @@ class StackVmProgram(val name: String, val heap: HeapValues) {
 
     fun optimize() {
         println("\nOptimizing stackVM code...")
+        optimizeDataConversionAndUselessDiscards()
+        // todo optimize stackvm code more
 
+        // remove nops (that are not a label)
+        this.instructions.removeIf { it.opcode==Opcode.NOP && it !is LabelInstr }
+    }
+
+    private fun optimizeDataConversionAndUselessDiscards() {
         // - push value followed by a data type conversion -> push the value in the correct type and remove the conversion
-        // - push somthing followed by a discard -> remove both
+        // - push something followed by a discard -> remove both
 
         val typeConversionOpcodes = setOf(
                 Opcode.LSB,
@@ -242,11 +249,6 @@ class StackVmProgram(val name: String, val heap: HeapValues) {
         for(rins in instructionsToReplace) {
             instructions[rins.key] = rins.value
         }
-
-        // remove nops (that are not a label)
-        this.instructions.removeIf { it.opcode==Opcode.NOP && it !is LabelInstr }
-
-        // todo optimize stackvm code more
     }
 
     fun blockvar(scopedname: String, decl: VarDecl) {
@@ -329,7 +331,7 @@ class Compiler(private val options: CompilationOptions) {
 
         val translator = StatementTranslator(intermediate, namespace, heap)
         translator.process(module)
-        println(" ${translator.stmtUniqueSequenceNr} source statements,  ${intermediate.numInstructions} resulting instructions")
+        println(" ${intermediate.numInstructions} vm instructions")
 
         return intermediate
     }
@@ -350,7 +352,7 @@ class Compiler(private val options: CompilationOptions) {
 private class StatementTranslator(private val stackvmProg: StackVmProgram,
                                   private val namespace: INameScope,
                                   private val heap: HeapValues): IAstProcessor {
-    var stmtUniqueSequenceNr = 0
+    var generatedLabelSequenceNumber = 0
         private set
 
     val breakStmtLabelStack : Stack<String> = Stack()
@@ -387,7 +389,7 @@ private class StatementTranslator(private val stackvmProg: StackVmProgram,
 
     private fun translate(statements: List<IStatement>) {
         for (stmt: IStatement in statements) {
-            stmtUniqueSequenceNr++
+            generatedLabelSequenceNumber++
             when (stmt) {
                 is Label -> translate(stmt)
                 is Return -> translate(stmt)
@@ -592,7 +594,10 @@ private class StatementTranslator(private val stackvmProg: StackVmProgram,
         stackvmProg.instr(Opcode.NOP)
     }
 
-    private fun makeLabel(postfix: String): String = "_prog8stmt_${stmtUniqueSequenceNr}_$postfix"
+    private fun makeLabel(postfix: String): String {
+        generatedLabelSequenceNumber++
+        return "_prog8stmt_${generatedLabelSequenceNumber}_$postfix"
+    }
 
     private fun translate(stmt: IfStatement) {
         /*

compiler/src/prog8/optimizing/Extensions.kt

@@ -33,9 +33,14 @@ fun Module.constantFold(globalNamespace: INameScope, heap: HeapValues) {
 fun Module.optimizeStatements(globalNamespace: INameScope, heap: HeapValues): Int {
     val optimizer = StatementOptimizer(globalNamespace, heap)
     this.process(optimizer)
+    for(stmt in optimizer.statementsToRemove) {
+        val scope=stmt.definingScope()
+        scope.remove(stmt)
+    }
+    this.linkParents()  // re-link in final configuration
+
     if(optimizer.optimizationsDone > 0)
         println("[${this.name}] Debug: ${optimizer.optimizationsDone} statement optimizations performed")
-    this.linkParents()  // re-link in final configuration
     return optimizer.optimizationsDone
 }
 

compiler/src/prog8/optimizing/StatementOptimizer.kt

@@ -24,11 +24,11 @@ import prog8.functions.BuiltinFunctions
     todo inline subroutines that are "sufficiently small"
 */
 
-class StatementOptimizer(private val globalNamespace: INameScope, private val heap: HeapValues) : IAstProcessor {
+class StatementOptimizer(private val namespace: INameScope, private val heap: HeapValues) : IAstProcessor {
     var optimizationsDone: Int = 0
         private set
-
-    private var statementsToRemove = mutableListOf<IStatement>()
+    var statementsToRemove = mutableListOf<IStatement>()
+        private set
     private val pureBuiltinFunctions = BuiltinFunctions.filter { it.value.pure }
 
     override fun process(functionCall: FunctionCallStatement): IStatement {
@@ -40,20 +40,59 @@ class StatementOptimizer(private val globalNamespace: INameScope, private val he
             }
         }
 
+        // if it calls a subroutine,
+        // and the first instruction in the subroutine is a jump, call that jump target instead
+        val subroutine = functionCall.target.targetStatement(namespace) as? Subroutine
+        if(subroutine!=null) {
+            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
+            if(first is Jump && first.identifier!=null) {
+                optimizationsDone++
+                return FunctionCallStatement(first.identifier, functionCall.arglist, functionCall.position)
+            }
+        }
+
         return super.process(functionCall)
     }
 
+    override fun process(functionCall: FunctionCall): IExpression {
+        // if it calls a subroutine,
+        // and the first instruction in the subroutine is a jump, call that jump target instead
+        val subroutine = functionCall.target.targetStatement(namespace) as? Subroutine
+        if(subroutine!=null) {
+            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
+            if(first is Jump && first.identifier!=null) {
+                optimizationsDone++
+                return FunctionCall(first.identifier, functionCall.arglist, functionCall.position)
+            }
+        }
+        return super.process(functionCall)
+    }
+
+    override fun process(returnStmt: Return): IStatement {
+        // if the return value is a subroutine call, replace this with a jump to the subroutine
+        if(returnStmt.values.size==1 && returnStmt.values[0] is FunctionCall) {
+            val call = returnStmt.values[0] as FunctionCall
+            if(call.target.targetStatement(namespace) is Subroutine) {
+                optimizationsDone++
+                return Jump(null, call.target, null, call.position)
+            }
+        }
+        return super.process(returnStmt)
+    }
+
     override fun process(ifStatement: IfStatement): IStatement {
         super.process(ifStatement)
-        val constvalue = ifStatement.condition.constValue(globalNamespace, heap)
+        val constvalue = ifStatement.condition.constValue(namespace, heap)
         if(constvalue!=null) {
             return if(constvalue.asBooleanValue){
                 // always true -> keep only if-part
                 printWarning("condition is always true", ifStatement.position)
+                optimizationsDone++
                 ifStatement.truepart
             } else {
                 // always false -> keep only else-part
                 printWarning("condition is always false", ifStatement.position)
+                optimizationsDone++
                 ifStatement.elsepart
             }
         }
@@ -69,6 +108,7 @@ class StatementOptimizer(private val globalNamespace: INameScope, private val he
                 // loopvar/reg = range value , follow by block
                 val assignment = Assignment(AssignTarget(forLoop.loopRegister, forLoop.loopVar, null, forLoop.position), null, range.from, forLoop.position)
                 forLoop.body.statements.add(0, assignment)
+                optimizationsDone++
                 return forLoop.body
             }
         }
@@ -77,15 +117,22 @@ class StatementOptimizer(private val globalNamespace: INameScope, private val he
 
     override fun process(whileLoop: WhileLoop): IStatement {
         super.process(whileLoop)
-        val constvalue = whileLoop.condition.constValue(globalNamespace, heap)
+        val constvalue = whileLoop.condition.constValue(namespace, heap)
         if(constvalue!=null) {
             return if(constvalue.asBooleanValue){
-                // always true
+                // always true -> print a warning, and optimize into body + jump
                 printWarning("condition is always true", whileLoop.position)
-                whileLoop
+                val label = Label("__back", whileLoop.condition.position)
+                whileLoop.body.statements.add(0, label)
+                whileLoop.body.statements.add(Jump(null,
+                        IdentifierReference(listOf("__back"), whileLoop.condition.position),
+                        null, whileLoop.condition.position))
+                optimizationsDone++
+                return whileLoop.body
             } else {
                 // always false -> ditch whole statement
                 printWarning("condition is always false", whileLoop.position)
+                optimizationsDone++
                 AnonymousScope(mutableListOf(), whileLoop.position)
             }
         }
@@ -94,18 +141,38 @@ class StatementOptimizer(private val globalNamespace: INameScope, private val he
 
     override fun process(repeatLoop: RepeatLoop): IStatement {
         super.process(repeatLoop)
-        val constvalue = repeatLoop.untilCondition.constValue(globalNamespace, heap)
+        val constvalue = repeatLoop.untilCondition.constValue(namespace, heap)
         if(constvalue!=null) {
             return if(constvalue.asBooleanValue){
                 // always true -> keep only the statement block
                 printWarning("condition is always true", repeatLoop.position)
+                optimizationsDone++
                 repeatLoop.body
             } else {
-                // always false
+                // always false -> print a warning, and optimize into body + jump
                 printWarning("condition is always false", repeatLoop.position)
-                repeatLoop
+                val label = Label("__back", repeatLoop.untilCondition.position)
+                repeatLoop.body.statements.add(0, label)
+                repeatLoop.body.statements.add(Jump(null,
+                        IdentifierReference(listOf("__back"), repeatLoop.untilCondition.position),
+                        null, repeatLoop.untilCondition.position))
+                optimizationsDone++
+                return repeatLoop.body
             }
         }
         return repeatLoop
     }
+
+    override fun process(jump: Jump): IStatement {
+        val subroutine = jump.identifier?.targetStatement(namespace) as? Subroutine
+        if(subroutine!=null) {
+            // if the first instruction in the subroutine is another jump, shortcut this one
+            val first = subroutine.statements.asSequence().filterNot { it is VarDecl || it is Directive }.firstOrNull()
+            if(first is Jump) {
+                optimizationsDone++
+                return first
+            }
+        }
+        return jump
+    }
 }