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preparing to optimize 16 bit repeat loop

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This commit is contained in:
Irmen de Jong 2021-02-28 17:00:52 +01:00
parent 9fe32c1c34
commit 07b5c44a54
2 changed files with 42 additions and 58 deletions
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62
compiler/src/prog8/compiler/target/cpu6502/codegen/AsmGen.kt
View File

@ -976,10 +976,12 @@ internal class AsmGen(private val program: Program,
val name = asmVariableName(stmt.iterations as IdentifierReference)
when(vardecl.datatype) {
DataType.UBYTE, DataType.BYTE -> {
repeatByteCountVar(name, repeatLabel, endLabel, stmt.body)
assignVariableToRegister(name, RegisterOrPair.A)
repeatByteCountInA(null, repeatLabel, endLabel, stmt.body)
}
DataType.UWORD, DataType.WORD -> {
repeatWordCountVar(name, repeatLabel, endLabel, stmt.body)
assignVariableToRegister(name, RegisterOrPair.AY)
repeatWordCountInAY(null, repeatLabel, endLabel, stmt.body)
}
else -> throw AssemblyError("invalid loop variable datatype $vardecl")
}
@ -1009,22 +1011,26 @@ internal class AsmGen(private val program: Program,
if(constIterations==0)
return
// note: A/Y must have been loaded with the number of iterations already!
// TODO can be even more optimized by iterating over pages
val counterVar = makeLabel("repeatcounter")
out("""
sta $counterVar
cmp #0
bne +
cpy #0
beq $endLabel ; skip if 0 iterations
+ sta $counterVar
sty $counterVar+1
$repeatLabel lda $counterVar
$repeatLabel
lda $counterVar
bne +
lda $counterVar+1
beq $endLabel
+ lda $counterVar
bne +
dec $counterVar+1
+ dec $counterVar
""")
+ dec $counterVar""")
translate(body)
jmp(repeatLabel)
if(constIterations!=null && constIterations>=16 && zeropage.available() > 1) {
// allocate count var on ZP
val zpAddr = zeropage.allocate(counterVar, DataType.UWORD, body.position, errors)
@ -1033,8 +1039,8 @@ $repeatLabel lda $counterVar
out("""
$counterVar .word 0""")
}
out(endLabel)
out(endLabel)
}
private fun repeatByteCountInA(constIterations: Int?, repeatLabel: String, endLabel: String, body: AnonymousScope) {
@ -1055,46 +1061,6 @@ $counterVar .byte 0""")
out(endLabel)
}
private fun repeatByteCountVar(repeatCountVar: String, repeatLabel: String, endLabel: String, body: AnonymousScope) {
// note: cannot use original counter variable because it should retain its original value
val counterVar = makeLabel("repeatcounter")
out(" lda $repeatCountVar | beq $endLabel | sta $counterVar")
out(repeatLabel)
translate(body)
out(" dec $counterVar | bne $repeatLabel")
// inline countervar:
out("""
beq $endLabel
$counterVar .byte 0""")
out(endLabel)
}
private fun repeatWordCountVar(repeatCountVar: String, repeatLabel: String, endLabel: String, body: AnonymousScope) {
// TODO can be even more optimized by iterating over pages
// note: cannot use original counter variable because it should retain its original value
val counterVar = makeLabel("repeatcounter")
out("""
lda $repeatCountVar
sta $counterVar
ora $repeatCountVar+1
beq $endLabel
lda $repeatCountVar+1
sta $counterVar+1""")
out(repeatLabel)
translate(body)
out("""
lda $counterVar
bne +
dec $counterVar+1
+ dec $counterVar
lda $counterVar
ora $counterVar+1
bne $repeatLabel
beq $endLabel
$counterVar .word 0""")
out(endLabel)
}
private fun translate(stmt: WhileLoop) {
checkBooleanExpression(stmt.condition) // we require the condition to be of the form 'x <comparison> <value>'
val booleanCondition = stmt.condition as BinaryExpression

24
examples/test.p8
View File

@ -7,17 +7,35 @@ main {
uword xx1
uword xx2
uword xx3
uword total
uword iterations
c64.SETTIM(0,0,0)
repeat 600 {
repeat 600 {
iterations = 0
repeat iterations {
repeat iterations {
xx1++
xx2++
xx3++
}
}
iterations = 600
repeat iterations {
repeat iterations {
xx1++
xx2++
xx3++
}
}
uword time = c64.RDTIM16()
txt.print("time: ")
txt.print_uw(time)
txt.print("\n$7e40? :\n")
txt.print_uwhex(xx1,true)
txt.nl()
txt.print_uwhex(xx2,true)
txt.nl()
txt.print_uwhex(xx3,true)
}
}