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add some more comparison expression optimizations to compare against 0 if possible

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This commit is contained in:
Irmen de Jong 2021-11-17 00:04:52 +01:00
parent f48d6ca9f8
commit 5d362047e2
2 changed files with 28 additions and 17 deletions
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20
codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
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@ -19,13 +19,7 @@ import kotlin.math.pow
Investigate what optimizations binaryen has, also see https://egorbo.com/peephole-optimizations.html
some of these may already be present:
X ^ -1 => ~x
X >= 1 => X > 0
X < 1 => X <= 0
and some const foldings (that may already be done as well):
Add some const foldings (that may already be done as well):
X + С1 == C2 => X == C2 - C1
((X + C1) + C2) => (X + (C1 + C2))
((X + C1) + (Y + C2)) => ((X + Y) + (C1 + C2))
@ -191,6 +185,12 @@ class ExpressionSimplifier(private val program: Program) : AstWalker() {
}
}
if(leftDt!=DataType.FLOAT && expr.operator == ">=" && rightVal?.number == 1.0) {
// for integers: x >= 1 --> x > 0
expr.operator = ">"
return listOf(IAstModification.ReplaceNode(expr.right, NumericLiteralValue.optimalInteger(0, expr.right.position), expr))
}
if(expr.operator == ">=" && rightVal?.number == 0.0) {
if (leftDt == DataType.UBYTE || leftDt == DataType.UWORD) {
// unsigned >= 0 --> true
@ -198,6 +198,12 @@ class ExpressionSimplifier(private val program: Program) : AstWalker() {
}
}
if(leftDt!=DataType.FLOAT && expr.operator == "<" && rightVal?.number == 1.0) {
// for integers: x < 1 --> x <= 0
expr.operator = "<="
return listOf(IAstModification.ReplaceNode(expr.right, NumericLiteralValue.optimalInteger(0, expr.right.position), expr))
}
if(expr.operator == "<" && rightVal?.number == 0.0) {
if (leftDt == DataType.UBYTE || leftDt == DataType.UWORD) {
// unsigned < 0 --> false

25
examples/test.p8
View File

@ -1,4 +1,5 @@
%import textio
%import floats
main {
@ -7,20 +8,24 @@ main {
ubyte xx = 1.234
ubyte yy = 2.234
uword aw
byte bb
float fl
; TODO: bitwise operations with a negative constant number -> replace the number by its positive 2 complement
aw = xx ^ 65535
aw = ~xx
yy = xx ^ 255
yy = ~xx
if aw<1
yy++
if aw<=0
yy++
; *(&X) => X
; X % 1 => 0
; X / 1 => X
; X ^ -1 => ~x
; X >= 1 => X > 0
; X < 1 => X <= 0
if yy<1
yy++
if yy<=0
yy++
if bb<1
yy++
if bb<=0
yy++
txt.print_ub(yy)
txt.print_uw(aw)