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print warning when bit shifts are too large and result in 0. #83

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This commit is contained in:
Irmen de Jong 2022-10-29 15:23:39 +02:00
parent 3f07cad35d
commit 6830e15b4e
4 changed files with 24 additions and 4 deletions
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8
codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
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@ -20,7 +20,9 @@ import kotlin.math.pow
// TODO add more peephole expression optimizations? Investigate what optimizations binaryen has, also see https://egorbo.com/peephole-optimizations.html
class ExpressionSimplifier(private val program: Program, private val compTarget: ICompilationTarget) : AstWalker() {
class ExpressionSimplifier(private val program: Program,
private val errors: IErrorReporter,
private val compTarget: ICompilationTarget) : AstWalker() {
private val powersOfTwo = (1..16).map { (2.0).pow(it) }.toSet()
private val negativePowersOfTwo = powersOfTwo.map { -it }.toSet()
@ -586,11 +588,13 @@ class ExpressionSimplifier(private val program: Program, private val compTarget:
when (val targetDt = targetIDt.getOr(DataType.UNDEFINED)) {
DataType.UBYTE, DataType.BYTE -> {
if (amount >= 8) {
errors.warn("shift always results in 0", expr.position)
return NumericLiteral(targetDt, 0.0, expr.position)
}
}
DataType.UWORD, DataType.WORD -> {
if (amount >= 16) {
errors.warn("shift always results in 0", expr.position)
return NumericLiteral(targetDt, 0.0, expr.position)
}
else if(amount==8) {
@ -625,6 +629,7 @@ class ExpressionSimplifier(private val program: Program, private val compTarget:
when (idt.getOr(DataType.UNDEFINED)) {
DataType.UBYTE -> {
if (amount >= 8) {
errors.warn("shift always results in 0", expr.position)
return NumericLiteral.optimalInteger(0, expr.position)
}
}
@ -636,6 +641,7 @@ class ExpressionSimplifier(private val program: Program, private val compTarget:
}
DataType.UWORD -> {
if (amount >= 16) {
errors.warn("shift always results in 0", expr.position)
return NumericLiteral.optimalInteger(0, expr.position)
}
else if(amount==8) {

4
codeOptimizers/src/prog8/optimizer/Extensions.kt
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@ -60,8 +60,8 @@ fun Program.inlineSubroutines(): Int {
return inliner.applyModifications()
}
fun Program.simplifyExpressions(target: ICompilationTarget) : Int {
val opti = ExpressionSimplifier(this, target)
fun Program.simplifyExpressions(errors: IErrorReporter, target: ICompilationTarget) : Int {
val opti = ExpressionSimplifier(this, errors, target)
opti.visit(this)
return opti.applyModifications()
}

2
compiler/src/prog8/compiler/Compiler.kt
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@ -361,7 +361,7 @@ private fun optimizeAst(program: Program, compilerOptions: CompilationOptions, e
remover.applyModifications()
while (true) {
// keep optimizing expressions and statements until no more steps remain
val optsDone1 = program.simplifyExpressions(compTarget)
val optsDone1 = program.simplifyExpressions(errors, compTarget)
val optsDone2 = program.splitBinaryExpressions(compilerOptions)
val optsDone3 = program.optimizeStatements(errors, functions, compTarget)
val optsDone4 = program.inlineSubroutines()

14
compiler/src/prog8/compiler/astprocessing/BeforeAsmTypecastCleaner.kt
View File

@ -129,4 +129,18 @@ internal class BeforeAsmTypecastCleaner(val program: Program,
}
return noModifications
}
override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
if(expr.operator=="<<" || expr.operator==">>") {
val shifts = expr.right.constValue(program)
if(shifts!=null) {
val dt = expr.left.inferType(program)
if(dt.istype(DataType.UBYTE) && shifts.number>=8.0)
errors.warn("shift always results in 0", expr.position)
if(dt.istype(DataType.UWORD) && shifts.number>=16.0)
errors.warn("shift always results in 0", expr.position)
}
}
return noModifications
}
}