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6502: Functions shouldn't use index registers if not necessary

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This commit is contained in:
Karol Stasiak 2019-03-18 21:54:26 +01:00
parent c829c5eb37
commit 69ccd993b2
4 changed files with 119 additions and 1 deletions
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2
src/main/scala/millfork/OptimizationPresets.scala
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@ -253,6 +253,8 @@ object OptimizationPresets {
AlwaysGoodOptimizations.TailCallOptimization,
AlwaysGoodOptimizations.UnusedCodeRemoval,
AlwaysGoodOptimizations.UnusedLabelRemoval,
UseAccumulatorInsteadOfXRegister,
UseAccumulatorInsteadOfYRegister,
VariableToRegisterOptimization,
TwoVariablesToIndexRegistersOptimization,
)

2
src/main/scala/millfork/assembly/mos/AssemblyLine.scala
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@ -553,7 +553,7 @@ case class AssemblyLine(opcode: Opcode.Value, addrMode: AddrMode.Value, var para
def concernsX: Boolean = addrMode == AbsoluteX || addrMode == LongAbsoluteX || addrMode == ZeroPageX || addrMode == IndexedX || ConcernsXAlways(opcode)
def concernsY: Boolean = addrMode == AbsoluteY || addrMode == ZeroPageY || addrMode == IndexedY || addrMode == LongIndexedY || ConcernsYAlways(opcode)
def concernsY: Boolean = addrMode == AbsoluteY || addrMode == ZeroPageY || addrMode == IndexedY || addrMode == IndexedSY || addrMode == LongIndexedY || ConcernsYAlways(opcode)
def treatment(state: State.Value): Treatment.Value = opcode match {
case LABEL => Unchanged // TODO: ???

95
src/main/scala/millfork/assembly/mos/opt/UseAccumulatorInsteadOfIndexRegister.scala Normal file
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@ -0,0 +1,95 @@
package millfork.assembly.mos.opt
import millfork.CompilationFlag
import millfork.assembly.{AssemblyOptimization, OptimizationContext}
import millfork.assembly.mos.{AssemblyLine, AssemblyLine0, OpcodeClasses}
import millfork.env.NormalFunction
import scala.collection.mutable
/**
* @author Karol Stasiak
*/
object UseAccumulatorInsteadOfYRegister extends UseAccumulatorInsteadOfIndexRegister(true)
object UseAccumulatorInsteadOfXRegister extends UseAccumulatorInsteadOfIndexRegister(false)
class UseAccumulatorInsteadOfIndexRegister(doY: Boolean) extends AssemblyOptimization[AssemblyLine] {
override def name: String = if (doY) "Use accumulator instead of the Y register" else "Use accumulator instead of the X register"
override def optimize(f: NormalFunction, code: List[AssemblyLine], context: OptimizationContext): List[AssemblyLine] = {
val log = context.log
if (f.params.length == 1) return code
if (!doY && f.returnType.size == 2) return code
val requiresResult = f.returnType.size == 1 || f.returnType.size == 2
if (doY) {
if (!code.exists(line => line.concernsY)) return code
} else {
if (!code.exists(line => line.concernsX)) return code
}
var resultDumped = true
val result = mutable.ListBuffer[AssemblyLine]()
val supportsInc = context.options.flag(CompilationFlag.EmitCmosOpcodes)
for(line <- code) {
import millfork.assembly.mos.Opcode._
import millfork.assembly.mos.AddrMode._
if (doY) {
if (OpcodeClasses.ChangesY(line.opcode)) resultDumped = false
} else {
if (OpcodeClasses.ChangesX(line.opcode)) resultDumped = false
}
line match {
case AssemblyLine0(_, ZeroPageY, _) => return code
case AssemblyLine0(_, AbsoluteY | ZeroPageY | IndexedSY | IndexedY | LongIndexedY, _) if doY => return code
case AssemblyLine0(_, AbsoluteX | ZeroPageX | IndexedX | LongAbsoluteX, _) if !doY => return code
case AssemblyLine0(SAY | SHY | XAA | LAS | AHX | SAX | HuSAX | SBX | SHX, _, _) => return code
case AssemblyLine0(TSX | TXS, _, _) if !doY => return code
case AssemblyLine0(INY, _, _) if doY =>
if (supportsInc) result += AssemblyLine.implied(INC)
else return code
case AssemblyLine0(INX, _, _) if !doY =>
if (supportsInc) result += AssemblyLine.implied(INC)
else return code
case AssemblyLine0(DEY, _, _) if doY =>
if (supportsInc) result += AssemblyLine.implied(DEC)
else return code
case AssemblyLine0(DEX, _, _) if !doY =>
if (supportsInc) result += AssemblyLine.implied(DEX)
else return code
case AssemblyLine0(LDY, _, _) if doY => result += line.copy(opcode = LDA)
case AssemblyLine0(LDX, _, _) if !doY => result += line.copy(opcode = LDA)
case AssemblyLine0(LAX, _, _) if !doY =>
result += line.copy(opcode = LDA)
resultDumped = true
case AssemblyLine0(STY, _, _) if doY => result += line.copy(opcode = STA)
case AssemblyLine0(STX, _, _) if !doY => result += line.copy(opcode = STA)
case AssemblyLine0(TYA, _, _) if doY =>
result += line.copy(opcode = TAY)
resultDumped = true
case AssemblyLine0(TXA, _, _) if !doY =>
result += line.copy(opcode = TAX)
resultDumped = true
case AssemblyLine0(CPY, _, _) if doY => result += line.copy(opcode = CMP)
case AssemblyLine0(CPX, _, _) if !doY => result += line.copy(opcode = CMP)
case AssemblyLine0(op, _, _) if OpcodeClasses.NoopDiscardsFlags(op) => result += line
case AssemblyLine0(op, _, _) if OpcodeClasses.ConcernsAAlways(op) => return code
case AssemblyLine0(op, Implied, _) if OpcodeClasses.ConcernsAIfImplied(op) => return code
case AssemblyLine0(RTS | RTI | JMP, _, _) =>
if (requiresResult && !resultDumped) return code
else result += line
case AssemblyLine0(LABEL, _, _) =>
resultDumped = false
result += line
case AssemblyLine0(op, _, _) if OpcodeClasses.ShortBranching(op) => result += line
case AssemblyLine0(op, _, _) if !OpcodeClasses.AllLinear(op) => return code
case _ => result += line
}
}
log.debug(name)
if (log.traceEnabled) {
code.foreach(l => log.trace(l.toString))
log.trace(" ↓")
result.foreach(l => log.trace(l.toString))
}
result.toList
}
}

21
src/test/scala/millfork/test/AssemblyOptimizationSuite.scala
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@ -637,4 +637,25 @@ class AssemblyOptimizationSuite extends FunSuite with Matchers {
}
}
test("Using accumulator") {
EmuCrossPlatformBenchmarkRun(Cpu.Mos)(
"""
|
|byte __last_used_device @$ba
|noinline byte last_used_device() {
| byte device
| device = __last_used_device
| if device == 0 { device = 8 }
| return device
|}
|
|
|void main() {
| last_used_device()
|}
""".stripMargin
) { m =>
}
}
}