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add assignment optimization X=value-X --> X=-X ; X+=value (to avoid need of stack-evaluation)

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Irmen de Jong 2021-11-20 23:43:10 +01:00
parent 107935ed31
commit 2491509c6a
1 changed files with 13 additions and 1 deletions
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14
codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt
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@ -355,14 +355,26 @@ class StatementOptimizer(private val program: Program,
throw FatalAstException("can't infer type of assignment target")
// optimize binary expressions a bit
val targetDt = targetIDt.getOr(DataType.UNDEFINED)
val bexpr=assignment.value as? BinaryExpression
if(bexpr!=null) {
val rightCv = bexpr.right.constValue(program)?.number
if(bexpr.operator=="-" && rightCv==null) {
if(bexpr.right isSameAs assignment.target) {
// X = value - X --> X = -X ; X += value (to avoid need of stack-evaluation)
val negation = PrefixExpression("-", bexpr.right.copy(), bexpr.position)
val addValue = Assignment(assignment.target.copy(), BinaryExpression(bexpr.right, "+", bexpr.left, bexpr.position), assignment.position)
return listOf(
IAstModification.ReplaceNode(bexpr, negation, assignment),
IAstModification.InsertAfter(assignment, addValue, parent as IStatementContainer)
)
}
}
if (rightCv != null && assignment.target isSameAs bexpr.left) {
// assignments of the form: X = X <operator> <expr>
// remove assignments that have no effect (such as X=X+0)
// optimize/rewrite some other expressions
val targetDt = targetIDt.getOr(DataType.UNDEFINED)
val vardeclDt = (assignment.target.identifier?.targetVarDecl(program))?.type
when (bexpr.operator) {
"+" -> {