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get rid of failed mccarthy shortcut evaluation
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Irmen de Jong
parent
af98d01053
commit
06184bdcb1
@ -200,17 +200,6 @@ internal class StatementReorderer(val program: Program,
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&& maySwapOperandOrder(expr))
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return listOf(IAstModification.SwapOperands(expr))
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if (expr.operator == "and") {
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val leftBinExpr = expr.left as? BinaryExpression
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if (leftBinExpr?.operator == "and")
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return mcCarthyAndExpression(expr, parent)
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}
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if (expr.operator == "or") {
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val leftBinExpr = expr.left as? BinaryExpression
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if (leftBinExpr?.operator == "or")
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return mcCarthyOrExpression(expr, parent)
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}
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// when using a simple bit shift and assigning it to a variable of a different type,
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// try to make the bit shifting 'wide enough' to fall into the variable's type.
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// with this, for instance, uword x = 1 << 10 will result in 1024 rather than 0 (the ubyte result).
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@ -332,17 +321,6 @@ internal class StatementReorderer(val program: Program,
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// rewrite in-place assignment expressions a bit so that the assignment target usually is the leftmost operand
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val binExpr = assignment.value as? BinaryExpression
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if(binExpr!=null) {
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if (binExpr.operator == "and") {
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val leftBinExpr = binExpr.left as? BinaryExpression
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if (leftBinExpr?.operator == "and")
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return mcCarthyAndAssignment(binExpr, assignment, parent)
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}
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if (binExpr.operator == "or") {
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val leftBinExpr = binExpr.left as? BinaryExpression
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if (leftBinExpr?.operator == "or")
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return mcCarthyOrAssignment(binExpr, assignment, parent)
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}
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if(binExpr.left isSameAs assignment.target) {
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// A = A <operator> 5, unchanged
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return noModifications
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@ -448,124 +426,6 @@ internal class StatementReorderer(val program: Program,
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checkUnusedReturnValues(functionCallStatement, function, errors)
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return tryReplaceCallWithGosub(functionCallStatement, parent, program, options)
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}
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private fun mcCarthyAndAssignment(andExpr: BinaryExpression, assignment: Assignment, assignmentParent: Node): Iterable<IAstModification> {
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val terms = findTerms(andExpr, "and")
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if(terms.any { it.constValue(program)?.asBooleanValue == false }) {
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errors.warn("expression is always false", andExpr.position)
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return listOf(IAstModification.ReplaceNode(andExpr, NumericLiteral.fromBoolean(false, andExpr.position), assignment))
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}
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val replacement = doShortcutEvaluation(
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assignment.target,
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assignment.target.inferType(program).getOr(DataType.UNDEFINED),
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terms,
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"==",
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false,
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assignment.position
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)
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return listOf(IAstModification.ReplaceNode(assignment, replacement, assignmentParent))
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}
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private fun mcCarthyOrAssignment(orExpr: BinaryExpression, assignment: Assignment, assignmentParent: Node): Iterable<IAstModification> {
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val terms = findTerms(orExpr, "or")
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if(terms.any { it.constValue(program)?.asBooleanValue == true }) {
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errors.warn("expression is always true", orExpr.position)
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return listOf(IAstModification.ReplaceNode(orExpr, NumericLiteral.fromBoolean(true, orExpr.position), assignment))
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}
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val replacement = doShortcutEvaluation(
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assignment.target,
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assignment.target.inferType(program).getOr(DataType.UNDEFINED),
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terms,
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"!=",
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false,
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assignment.position
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)
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return listOf(IAstModification.ReplaceNode(assignment, replacement, assignmentParent))
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}
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private fun mcCarthyAndExpression(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
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val terms = findTerms(expr, "and")
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if(terms.any { it.constValue(program)?.asBooleanValue == false }) {
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errors.warn("expression is always false", expr.position)
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return listOf(IAstModification.ReplaceNode(expr, NumericLiteral.fromBoolean(false, expr.position), parent))
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}
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val (tempvarName, _) = program.getTempVar(DataType.UBYTE)
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val assignTarget = AssignTarget(IdentifierReference(tempvarName, expr.position), null, null, position = expr.position)
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val replacement = doShortcutEvaluation(assignTarget, DataType.UBYTE, terms, "==", true, expr.position)
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val exprStmt = expr.containingStatement
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return listOf(
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IAstModification.InsertBefore(exprStmt, replacement, exprStmt.definingScope),
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IAstModification.ReplaceNode(expr, assignTarget.identifier!!.copy(), parent)
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)
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}
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private fun mcCarthyOrExpression(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
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val terms = findTerms(expr, "or")
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if(terms.any { it.constValue(program)?.asBooleanValue == true }) {
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errors.warn("expression is always true", expr.position)
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return listOf(IAstModification.ReplaceNode(expr, NumericLiteral.fromBoolean(false, expr.position), parent))
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}
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val (tempvarName, _) = program.getTempVar(DataType.UBYTE)
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val assignTarget = AssignTarget(IdentifierReference(tempvarName, expr.position), null, null, position = expr.position)
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val replacement = doShortcutEvaluation(assignTarget, DataType.UBYTE, terms, "!=", true, expr.position)
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val exprStmt = expr.containingStatement
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return listOf(
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IAstModification.InsertBefore(exprStmt, replacement, exprStmt.definingScope),
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IAstModification.ReplaceNode(expr, assignTarget.identifier!!.copy(), parent)
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)
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}
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private fun findTerms(expr: BinaryExpression, operator: String, terms: List<Expression> = emptyList()): List<Expression> {
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if(expr.operator!=operator)
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return listOf(expr) + terms
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val leftBinExpr = expr.left as? BinaryExpression ?: return listOf(expr.left, expr.right) + terms
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return findTerms(leftBinExpr, operator, listOf(expr.right)+terms)
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}
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private fun doShortcutEvaluation(
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target: AssignTarget,
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targetDt: DataType,
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terms: List<Expression>,
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checkZeroOperator: String,
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convertToBool: Boolean,
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position: Position
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): AnonymousScope {
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val replacement = AnonymousScope(mutableListOf(), position)
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val doneLabel = program.makeLabel("and", position)
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for ((idx, term) in terms.withIndex()) {
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val value: Expression = if (term is IFunctionCall
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&& term.target.nameInSource == listOf("boolean")
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&& term.args[0].inferType(program).isAssignableTo(targetDt)
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)
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term.args[0].copy()
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else
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term.copy()
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val assignTerm = Assignment(target.copy(), value, AssignmentOrigin.OPTIMIZER, position)
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replacement.statements.add(assignTerm)
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if (idx < terms.size - 1) {
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val targetCheck = BinaryExpression(target.toExpression(), checkZeroOperator,
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NumericLiteral(DataType.UBYTE, 0.0, position), position)
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val jumpDone = program.jumpLabel(doneLabel)
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val ifStmt = IfElse(targetCheck,
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AnonymousScope(mutableListOf(jumpDone), position),
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AnonymousScope(mutableListOf(), Position.DUMMY),
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position)
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replacement.statements.add(ifStmt)
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} else if(idx==terms.size-1) {
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if(convertToBool) {
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assignTerm.value = BuiltinFunctionCall(IdentifierReference(listOf("boolean"), assignTerm.position), mutableListOf(value), assignTerm.position)
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}
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if(targetDt !in ByteDatatypes)
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assignTerm.value = TypecastExpression(assignTerm.value, targetDt, true, assignTerm.position)
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}
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}
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replacement.statements.add(doneLabel)
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return replacement
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}
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}
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@ -489,9 +489,8 @@ logical: ``not`` ``and`` ``or`` ``xor``
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.. note::
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Unlike most other programming languages, there is no short-cirquit or McCarthy-evaluation
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for the ``and`` and ``or`` operators at this time. This means that prog8 currently always evaluates
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all operands from these logical expressions, even when one of them already determines the outcome.
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This may be changed in a future language version.
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for the logical ``and`` and ``or`` operators. This means that prog8 currently always evaluates
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all operands from these logical expressions, even when one of them already determines the outcome!
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range creation: ``to``
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Creates a range of values from the LHS value to the RHS value, inclusive.
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@ -3,10 +3,6 @@ TODO
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For next release
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^^^^^^^^^^^^^^^^
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- add McCarthy evaluation to shortcircuit and/or expressions. Both conditional expressions and assignments!
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StatementReorder.after(assignment).
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TODO: boolean expressions.
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- add unit tests for all 4 mcarthy shortcut cases.
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- can we optimize redundant calls to boolean() away? imageviewer.prg got larger because of them
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- add some more optimizations in vmPeepholeOptimizer
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- vm Instruction needs to know what the read-registers/memory are, and what the write-register/memory is.
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@ -1,7 +1,7 @@
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%import textio
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%zeropage basicsafe
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; NOTE: meant to test to virtual machine output target (use -target vitual)
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; NOTE: meant to test to virtual machine output target (use -target virtual)
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main {
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