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slight expression rewrite in case of certain in-place assignments, to try to get the in-place variable operand to the leftmost position

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This commit is contained in:
Irmen de Jong 2020-07-30 01:30:21 +02:00
parent 7ac6c8f2d1
commit fbe3ce008b
8 changed files with 116 additions and 42 deletions
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1
compiler/src/prog8/ast/AstToSourceCode.kt
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@ -289,6 +289,7 @@ class AstToSourceCode(val output: (text: String) -> Unit, val program: Program):
override fun visit(assignment: Assignment) {
val binExpr = assignment.value as? BinaryExpression
if(binExpr!=null && binExpr.left isSameAs assignment.target) {
// we only support the inplace assignments of the form A = A <operator> <value>
assignment.target.accept(this)
output(" ${binExpr.operator}= ")
binExpr.right.accept(this)

51
compiler/src/prog8/ast/processing/StatementReorderer.kt
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@ -14,8 +14,8 @@ internal class StatementReorderer(val program: Program) : AstWalker() {
// - in every scope, most directives and vardecls are moved to the top.
// - the 'start' subroutine is moved to the top.
// - (syntax desugaring) a vardecl with a non-const initializer value is split into a regular vardecl and an assignment statement.
// - (syntax desugaring) augmented assignment is turned into regular assignment.
// - (syntax desugaring) struct value assignment is expanded into several struct member assignments.
// - in-place assignments are reordered a bit so that they are mostly of the form A = A <operator> <rest>
// - sorts the choices in when statement.
// - insert AddressOf (&) expression where required (string params to a UWORD function param etc).
@ -118,6 +118,55 @@ internal class StatementReorderer(val program: Program) : AstWalker() {
return noModifications
}
override fun after(assignment: Assignment, parent: Node): Iterable<IAstModification> {
// rewrite in-place assignment expressions a bit so that the assignment target usually is the leftmost operand
val binExpr = assignment.value as? BinaryExpression
if(binExpr!=null) {
if(binExpr.left isSameAs assignment.target) {
// A = A <operator> 5, unchanged
return noModifications
}
if(binExpr.operator in associativeOperators) {
if (binExpr.right isSameAs assignment.target) {
// A = v <associative-operator> A ==> A = A <associative-operator> v
return listOf(IAstModification.SwapOperands(binExpr))
}
val leftBinExpr = binExpr.left as? BinaryExpression
if(leftBinExpr?.operator == binExpr.operator) {
return if(leftBinExpr.left isSameAs assignment.target) {
// A = (A <associative-operator> x) <same-operator> y ==> A = A <associative-operator> (x <same-operator> y)
val newRight = BinaryExpression(leftBinExpr.right, binExpr.operator, binExpr.right, binExpr.position)
val newValue = BinaryExpression(leftBinExpr.left, binExpr.operator, newRight, binExpr.position)
listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
} else {
// A = (x <associative-operator> A) <same-operator> y ==> A = A <associative-operator> (x <same-operator> y)
val newRight = BinaryExpression(leftBinExpr.left, binExpr.operator, binExpr.right, binExpr.position)
val newValue = BinaryExpression(leftBinExpr.right, binExpr.operator, newRight, binExpr.position)
listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
}
}
val rightBinExpr = binExpr.right as? BinaryExpression
if(rightBinExpr?.operator == binExpr.operator) {
return if(rightBinExpr.left isSameAs assignment.target) {
// A = x <associative-operator> (A <same-operator> y) ==> A = A <associative-operator> (x <same-operator> y)
val newRight = BinaryExpression(binExpr.left, binExpr.operator, rightBinExpr.right, binExpr.position)
val newValue = BinaryExpression(rightBinExpr.left, binExpr.operator, newRight, binExpr.position)
listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
} else {
// A = x <associative-operator> (y <same-operator> A) ==> A = A <associative-operator> (x <same-operator> y)
val newRight = BinaryExpression(binExpr.left, binExpr.operator, rightBinExpr.left, binExpr.position)
val newValue = BinaryExpression(rightBinExpr.right, binExpr.operator, newRight, binExpr.position)
listOf(IAstModification.ReplaceNode(binExpr, newValue, assignment))
}
}
}
}
return noModifications
}
private fun flattenStructAssignmentFromStructLiteral(structAssignment: Assignment, program: Program): List<Assignment> {
val identifier = structAssignment.target.identifier!!
val identifierName = identifier.nameInSource.single()

29
compiler/src/prog8/ast/statements/AstStatements.kt
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@ -348,6 +348,35 @@ open class Assignment(var target: AssignTarget, var value: Expression, override
override fun toString(): String {
return("Assignment(target: $target, value: $value, pos=$position)")
}
val isInplace: Boolean
get() {
val binExpr = value as? BinaryExpression
if(binExpr!=null) {
if(binExpr.left isSameAs target)
return true // A = A <operator> 5
if(binExpr.operator in associativeOperators) {
if (binExpr.right isSameAs target)
return true // A = v <associative-operator> A
val leftBinExpr = binExpr.left as? BinaryExpression
if(leftBinExpr?.operator == binExpr.operator) {
// A = (A <associative-operator> x) <same-operator> y
// A = (x <associative-operator> A) <same-operator> y
return leftBinExpr.left isSameAs target || leftBinExpr.right isSameAs target
}
val rightBinExpr = binExpr.right as? BinaryExpression
if(rightBinExpr?.operator == binExpr.operator) {
// A = y <associative-operator> (A <same-operator> x)
// A = y <associative-operator> (x <same-operator> y)
return rightBinExpr.left isSameAs target || rightBinExpr.right isSameAs target
}
}
}
return false
}
}
data class AssignTarget(var identifier: IdentifierReference?,

2
compiler/src/prog8/compiler/Main.kt
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@ -192,7 +192,7 @@ private fun writeAssembly(programAst: Program, errors: ErrorReporter, outputDir:
programAst.processAstBeforeAsmGeneration(errors)
errors.handle()
printAst(programAst) // TODO
// printAst(programAst)
val assembly = CompilationTarget.asmGenerator(
programAst,

4
compiler/src/prog8/compiler/target/c64/codegen/AssignmentAsmGen.kt
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@ -18,7 +18,9 @@ import prog8.compiler.toHex
internal class AssignmentAsmGen(private val program: Program, private val errors: ErrorReporter, private val asmgen: AsmGen) {
internal fun translate(assign: Assignment) {
// TODO check for in-place assignment A = A <operator> X and generate better code for that
if(assign.isInplace)
translateNormalAssignment(assign) // TODO generate better code here for in-place assignments
else
translateNormalAssignment(assign)
}

4
compiler/src/prog8/optimizer/ExpressionSimplifier.kt
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@ -84,10 +84,6 @@ internal class ExpressionSimplifier(private val program: Program) : AstWalker()
}
override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
// TODO: (A +/- B) +/- C ==> A +/- ( B +/- C)
// TODO: (A * / B) * / C ==> A * / ( B * / C)
val leftVal = expr.left.constValue(program)
val rightVal = expr.right.constValue(program)

2
docs/source/syntaxreference.rst
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@ -404,7 +404,7 @@ assignment: ``=``
Note that an assignment sometimes is not possible or supported.
augmented assignment: ``+=`` ``-=`` ``*=`` ``/=`` ``**=`` ``&=`` ``|=`` ``^=`` ``<<=`` ``>>=``
Syntactic sugar; ``aa += xx`` is equivalent to ``aa = aa + xx``
This is syntactic sugar; ``aa += xx`` is equivalent to ``aa = aa + xx``
postfix increment and decrement: ``++`` ``--``
Syntactic sugar; ``aa++`` is equivalent to ``aa = aa + 1``, and ``aa--`` is equivalent to ``aa = aa - 1``.

63
examples/test.p8
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@ -4,11 +4,6 @@
%zeropage basicsafe
%option enable_floats
; todo: add these to the Expression Simplifier so that all the below assignments become a simple in-place assignment:
; (A +/- B) +/- C ==> A +/- ( B +/- C)
; (A * / B) * / C ==> A * / ( B * / C)
main {
sub start() {
@ -16,35 +11,37 @@ main {
ubyte wv
ubyte wv2
wv *= wv2
wv = wv + wv + wv
wv += 10
wv += 20
wv += 30
wv += 1 + wv2
wv += 2 + wv2
wv += 3 + wv2
wv += wv2 + 1
wv += wv2 + 2
wv += wv2 + 3
wv = wv + 1 + wv2
wv = wv + 2 + wv2
wv = wv + 3 + wv2
wv = 1 + wv2 + wv
wv = 2 + wv2 + wv
wv = 3 + wv2 + wv
wv = wv + wv2 + 1
wv = wv + wv2 + 2
wv = wv + wv2 + 3
wv = wv2 + 1 + wv
wv = wv2 + 2 + wv
wv = wv2 + 3 + wv
; wv *= wv2
;
; wv += 10
; wv += 20
; wv += 30
;
; wv += 1 + wv2
; wv += 2 + wv2
; wv += 3 + wv2
;
; wv += wv2 + 1
; wv += wv2 + 2
; wv += wv2 + 3
;
; wv = wv + 1 + wv2
; wv = wv + 2 + wv2
; wv = wv + 3 + wv2
;
; wv = 1 + wv2 + wv
; wv = 2 + wv2 + wv
; wv = 3 + wv2 + wv
;
; wv = wv + wv2 + 1
; wv = wv + wv2 + 2
; wv = wv + wv2 + 3
;
; wv = wv2 + 1 + wv
; wv = wv2 + 2 + wv
; wv = wv2 + 3 + wv
wv = wv2 + wv + 1
wv = wv2 + wv + 2