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add some more const folding patterns

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This commit is contained in:
Irmen de Jong 2021-11-20 22:33:13 +01:00
parent eacf8b896a
commit 31491c62c5
2 changed files with 47 additions and 25 deletions
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34
codeOptimizers/src/prog8/optimizer/ConstantFoldingOptimizer.kt
View File

@ -79,7 +79,7 @@ class ConstantFoldingOptimizer(private val program: Program) : AstWalker() {
return noModifications
}
/**
/*
* Try to constfold a binary expression.
* Compile-time constant sub expressions will be evaluated on the spot.
* For instance, "9 * (4 + 2)" will be optimized into the integer literal 54.
@ -186,13 +186,43 @@ class ConstantFoldingOptimizer(private val program: Program) : AstWalker() {
}
}
val evaluator = ConstExprEvaluator()
// const fold when both operands are a const
if(leftconst != null && rightconst != null) {
val evaluator = ConstExprEvaluator()
val result = evaluator.evaluate(leftconst, expr.operator, rightconst)
modifications += IAstModification.ReplaceNode(expr, result, parent)
}
val leftBinExpr = expr.left as? BinaryExpression
val rightBinExpr = expr.right as? BinaryExpression
if(expr.operator=="+" || expr.operator=="-") {
if(leftBinExpr!=null && rightBinExpr!=null) {
val c1 = leftBinExpr.right.constValue(program)
val c2 = rightBinExpr.right.constValue(program)
if(leftBinExpr.operator=="+" && rightBinExpr.operator=="+") {
if (c1 != null && c2 != null) {
// (X + C1) <plusmin> (Y + C2) => (X <plusmin> Y) + (C1 <plusmin> C2)
val c3 = evaluator.evaluate(c1, expr.operator, c2)
val xwithy = BinaryExpression(leftBinExpr.left, expr.operator, rightBinExpr.left, expr.position)
val newExpr = BinaryExpression(xwithy, "+", c3, expr.position)
modifications += IAstModification.ReplaceNode(expr, newExpr, parent)
}
}
else if(leftBinExpr.operator=="*" && rightBinExpr.operator=="*"){
if (c1 != null && c2 != null && c1==c2) {
//(X * C) <plusmin> (Y * C) => (X <plusmin> Y) * C
val xwithy = BinaryExpression(leftBinExpr.left, expr.operator, rightBinExpr.left, expr.position)
val newExpr = BinaryExpression(xwithy, "*", c1, expr.position)
modifications += IAstModification.ReplaceNode(expr, newExpr, parent)
}
}
}
}
return modifications
}

38
examples/test.p8
View File

@ -6,19 +6,11 @@ main {
ubyte xx = 1
ubyte yy = 2
byte b1
byte b2
;; TODO add these constant folders:
;
;; (X + C1) + (Y + C2) => (X + Y) + (C1 + C2)
;; (X + C1) - (Y + C2) => (X - Y) + (C1 - C2)
;; ---> together: (X + C1) <plusmin> (Y + C2) => (X <plusmin> Y) + (C1 <plusmin> C2)
;; (X * C) + (Y * C) => (X + Y) * C
;; (X * C) - (Y * C) => (X - Y) * C
;; ---> together: (X * C) <plusmin> (Y * C) => (X <plusmin> Y) * C
;
;; (X - C1) + (Y - C2) => (X + Y) - (C1 + C2)
;; (X - C1) <plusmin> (Y - C2) => (X <plusmin> Y) - (C1 <plusmin> C2)
;; (X - C1) - (Y - C2) => (X - Y) - (C1 - C2)
;
@ -43,22 +35,22 @@ main {
txt.print_ub(yy) ; 40
txt.nl()
xx=100
yy=8
yy = (xx+5)-(yy+10)
txt.print_ub(yy) ; 87
b1=100
b2=8
b2 = (b1+5)-(b2+10)
txt.print_b(b2) ; 87
txt.nl()
xx=50
yy=40
yy = (xx-5)+(yy-10)
txt.print_ub(yy) ; 75
b1=50
b2=40
b2 = (b1-5)+(b2-10)
txt.print_b(b2) ; 75
txt.nl()
xx=50
yy=20
yy = (xx-5)-(yy-10)
txt.print_ub(yy) ; 35
b1=50
b2=20
b2 = (b1-5)-(b2-10)
txt.print_b(b2) ; 35
txt.nl()
repeat {