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fix problematic optimizations to logical expressions

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This commit is contained in:
Irmen de Jong 2022-07-02 00:54:38 +02:00
parent 965340ff90
commit 24d13dd120
5 changed files with 37 additions and 107 deletions
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11
compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt
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@ -115,17 +115,6 @@ class AstPreprocessor(val program: Program, val errors: IErrorReporter, val comp
return noModifications
}
override fun after(expr: PrefixExpression, parent: Node): Iterable<IAstModification> {
if(expr.operator == "not") {
// not(x) --> x==0
// this means that "not" will never occur anywhere again in the ast after this
val dt = expr.expression.inferType(program).getOr(DataType.UBYTE)
val replacement = BinaryExpression(expr.expression, "==", NumericLiteral(dt,0.0, expr.position), expr.position)
return listOf(IAstModification.ReplaceNodeSafe(expr, replacement, parent))
}
return noModifications
}
override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
val nextAssignment = decl.nextSibling() as? Assignment
if(nextAssignment!=null && nextAssignment.origin!=AssignmentOrigin.VARINIT) {

55
compiler/src/prog8/compiler/astprocessing/NotExpressionChanger.kt
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@ -8,6 +8,7 @@ import prog8.ast.expressions.NumericLiteral
import prog8.ast.expressions.PrefixExpression
import prog8.ast.walk.AstWalker
import prog8.ast.walk.IAstModification
import prog8.code.core.DataType
import prog8.code.core.IErrorReporter
import prog8.code.core.IntegerDatatypes
@ -39,54 +40,6 @@ internal class NotExpressionChanger(val program: Program, val errors: IErrorRepo
}
}
}
val left = expr.left as? BinaryExpression
val right = expr.right as? BinaryExpression
val leftValue = left?.right?.constValue(program)?.number
val rightValue = right?.right?.constValue(program)?.number
if(expr.operator == "or") {
if(left?.operator=="==" && right?.operator=="==" && leftValue==0.0 && rightValue==0.0) {
// (a==0) or (b==0) -> (a and b)==0
val orExpr = BinaryExpression(left.left, "and", right.left, expr.position)
val equalsZero = BinaryExpression(orExpr, "==", NumericLiteral.fromBoolean(false, expr.position), expr.position)
return listOf(IAstModification.ReplaceNode(expr, equalsZero, parent))
}
}
else if(expr.operator == "and") {
if(left?.operator=="==" && right?.operator=="==" && leftValue==0.0 && rightValue==0.0) {
// (a==0) and (b==0) -> (a or b)==0
val orExpr = BinaryExpression(left.left, "or", right.left, expr.position)
val equalsZero = BinaryExpression(orExpr, "==", NumericLiteral.fromBoolean(false, expr.position), expr.position)
return listOf(IAstModification.ReplaceNode(expr, equalsZero, parent))
}
}
return noModifications
}
override fun after(expr: BinaryExpression, parent: Node): Iterable<IAstModification> {
// not a or not b -> not(a and b)
if(expr.operator=="or") {
val left = expr.left as? PrefixExpression
val right = expr.right as? PrefixExpression
if(left?.operator=="not" && right?.operator=="not") {
val andExpr = BinaryExpression(left.expression, "and", right.expression, expr.position)
val notExpr = PrefixExpression("not", andExpr, expr.position)
return listOf(IAstModification.ReplaceNode(expr, notExpr, parent))
}
}
// not a and not b -> not(a or b)
if(expr.operator=="and") {
val left = expr.left as? PrefixExpression
val right = expr.right as? PrefixExpression
if(left?.operator=="not" && right?.operator=="not") {
val andExpr = BinaryExpression(left.expression, "or", right.expression, expr.position)
val notExpr = PrefixExpression("not", andExpr, expr.position)
return listOf(IAstModification.ReplaceNode(expr, notExpr, parent))
}
}
return noModifications
}
@ -116,6 +69,12 @@ internal class NotExpressionChanger(val program: Program, val errors: IErrorRepo
return listOf(IAstModification.ReplaceNode(expr, subBinExpr, parent))
}
}
// all other not(x) --> x==0
// this means that "not" will never occur anywhere again in the ast after this
val dt = expr.expression.inferType(program).getOr(DataType.UBYTE)
val replacement = BinaryExpression(expr.expression, "==", NumericLiteral(dt,0.0, expr.position), expr.position)
return listOf(IAstModification.ReplaceNodeSafe(expr, replacement, parent))
}
return noModifications
}

22
compiler/test/TestOptimization.kt
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@ -251,15 +251,15 @@ class TestOptimization: FunSpec({
(initY2.value as NumericLiteral).number shouldBe 11.0
}
xtest("various 'not' operator rewrites even without optimizations on") {
test("various 'not' operator rewrites even without optimizations on") {
val src = """
main {
sub start() {
ubyte a1
ubyte a2
a1 = not not a1 ; a1 = a1==0
a1 = not a1 or not a2 ; a1 = (a1 and a2)==0
a1 = not a1 and not a2 ; a1 = (a1 or a2)==0
a1 = not a1 or not a2 ; a1 = a1==0 | a2==0
a1 = not a1 and not a2 ; a1 = a1==0 & a2==0
}
}
"""
@ -273,20 +273,8 @@ class TestOptimization: FunSpec({
val value3 = (stmts[6] as Assignment).value as BinaryExpression
value1.operator shouldBe "=="
value1.right shouldBe NumericLiteral(DataType.UBYTE, 0.0, Position.DUMMY)
value2.operator shouldBe "=="
value2.right shouldBe NumericLiteral(DataType.UBYTE, 0.0, Position.DUMMY)
value3.operator shouldBe "=="
value3.right shouldBe NumericLiteral(DataType.UBYTE, 0.0, Position.DUMMY)
val left1 = value1.left as IdentifierReference
val left2 = value2.left as BinaryExpression
val left3 = value3.left as BinaryExpression
left1.nameInSource shouldBe listOf("a1")
left2.operator shouldBe "and"
(left2.left as IdentifierReference).nameInSource shouldBe listOf("a1")
(left2.right as IdentifierReference).nameInSource shouldBe listOf("a2")
left3.operator shouldBe "or"
(left3.left as IdentifierReference).nameInSource shouldBe listOf("a1")
(left3.right as IdentifierReference).nameInSource shouldBe listOf("a2")
value2.operator shouldBe "|"
value3.operator shouldBe "&"
}
test("intermediate assignment steps generated for typecasted expression") {

4
docs/source/todo.rst
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@ -3,8 +3,6 @@ TODO
For next release
^^^^^^^^^^^^^^^^
- re-enable unittest "various 'not' operator rewrites even without optimizations on" when not-problem is fixed
- petaxian roller.p8 line 49 (also see test.p8) generates large code compared to 8.2
- code gen for if statements has become inefficient? vm/6502?
@ -22,8 +20,6 @@ For next release
- compiling logical.p8 to virtual with optimization generates a lot larger code as without optimizations.
this is not the case for the 6502 codegen.
- bin expr splitter: split logical expressions on ands/ors/xors ?
- add some more optimizations in vmPeepholeOptimizer
- vm Instruction needs to know what the read-registers/memory are, and what the write-register/memory is.
this info is needed for more advanced optimizations and later code generation steps.

52
examples/test.p8
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@ -8,41 +8,39 @@ main {
sub start() {
ubyte a1 = 0
ubyte a2 = 128
uword w1 = 0
ubyte vv
; if not a1 and not w1
; txt.print("1")
; if (0==a1) and (0==w1)
; txt.print("a")
; txt.nl()
a1 = 0
w1 = 4096
if not a1 and not w1
txt.print("fail ")
else
if not a1
txt.print("ok ")
if (0==a1) and (0==w1)
txt.print("fail ")
else
txt.print("ok ")
txt.print("fail ")
vv = not a1
txt.print_ub(vv)
txt.nl()
a1=128
w1=2
if not a1 and not w1
txt.print("fail")
if (0==a1) and (0==w1)
txt.print("fail")
if not a1
txt.print("fail ")
else
txt.print("ok ")
vv = not a1
txt.print_ub(vv)
txt.nl()
w1=2
if not a1 and not w1
txt.print("fail")
if (0==a1) and (0==w1)
txt.print("fail")
if not w1
txt.print("ok ")
else
txt.print("fail ")
vv = not w1
txt.print_ub(vv)
txt.nl()
w1 = 4096
if not w1
txt.print("fail ")
else
txt.print("ok ")
vv = not w1
txt.print_ub(vv)
txt.nl()
; petaxian roller.p8 line 49