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optimize pointer indexing a bit

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This commit is contained in:
Irmen de Jong 2024-02-03 23:11:53 +01:00
parent abcdfd8e28
commit 8e00408e3e
3 changed files with 47 additions and 31 deletions
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51
codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
View File

@ -797,7 +797,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
else
asmgen.out(" sec | sbc $arrayvarname,y")
assignRegisterByte(target, CpuRegister.A, dt in SignedDatatypes, true)
} else if(expr.operator=="+" && leftMemByte!=null && right.type in ByteDatatypes && optimizedPointerIndexPlusByteIntoA(leftMemByte, right)) {
} else if(expr.operator=="+" && leftMemByte!=null && right.type in ByteDatatypes && optimizedPointerIndexPlusMinusByteIntoA(right, "+", leftMemByte)) {
assignRegisterByte(target, CpuRegister.A, dt in SignedDatatypes, true)
return true
} else if(rightMemByte!=null && left.type in ByteDatatypes && optimizedPointerIndexPlusMinusByteIntoA(left, expr.operator, rightMemByte)) {
@ -987,29 +987,44 @@ internal class AssignmentAsmGen(private val program: PtProgram,
return false
}
private fun optimizedPointerIndexPlusByteIntoA(mem: PtMemoryByte, value: PtExpression): Boolean {
// special optimization for pointervar[y] + bytevalue (actually: @(address) + value)
return false // TODO implement this optimization?
}
private fun optimizedPointerIndexPlusMinusByteIntoA(value: PtExpression, operator: String, mem: PtMemoryByte): Boolean {
// special optimization for bytevalue +/- pointervar[y] (actually: bytevalue +/- @(address) )
val address = mem.address as? PtBinaryExpression
if(address is PtBinaryExpression) {
val offset = address.right.asConstInteger()
if(offset!=null && offset<256) {
// we have value + @(ptr + 255), or value - @(ptr+255)
// TODO()
} else if(address.right.type in ByteDatatypes) {
// we have @(ptr + bytevar) ++ , or @(ptr+bytevar)--
// TODO()
} else if((address.right as? PtTypeCast)?.value?.type in ByteDatatypes) {
// we have @(ptr + bytevar) ++ , or @(ptr+bytevar)--
// TODO()
val ptrVar = address.left as? PtIdentifier
if(ptrVar!=null && asmgen.isZpVar(ptrVar)) {
assignExpressionToRegister(value, RegisterOrPair.A, false)
val pointername = asmgen.asmVariableName(ptrVar)
val constOffset = address.right.asConstInteger()
if (constOffset != null && constOffset < 256) {
// we have value + @(zpptr + 255), or value - @(zpptr+255)
asmgen.out(" ldy #$constOffset")
if (operator == "+")
asmgen.out(" clc | adc ($pointername),y")
else
asmgen.out(" sec | sbc ($pointername),y")
} else if (address.right.type in ByteDatatypes) {
// we have @(ptr + bytevar) ++ , or @(ptr+bytevar)--
asmgen.out(" pha")
assignExpressionToRegister(address.right, RegisterOrPair.Y, false)
asmgen.out(" pla")
if (operator == "+")
asmgen.out(" clc | adc ($pointername),y")
else
asmgen.out(" sec | sbc ($pointername),y")
} else if ((address.right as? PtTypeCast)?.value?.type in ByteDatatypes) {
// we have @(ptr + bytevar as uword) ++ , or @(ptr+bytevar as uword)--
asmgen.out(" pha")
assignExpressionToRegister((address.right as PtTypeCast).value, RegisterOrPair.Y, false)
asmgen.out(" pla")
if (operator == "+")
asmgen.out(" clc | adc ($pointername),y")
else
asmgen.out(" sec | sbc ($pointername),y")
}
return true
}
}
println("TODO: OPTIMIZE POINTER PLUSMINUS ${value.position}")
return false
}

5
docs/source/todo.rst
View File

@ -1,10 +1,7 @@
TODO
====
petaxian is now a lot larger since pointer[idx] is rewritten into @(ptr+idx). Missing some optimized code somewhere now?
VM textelite is now a lot larger too
DO: "TODO implement this optimization"
VM textelite is now a lot larger due to the ptr[i] -> @(ptr+i) rewrite. Fix this.
(after merge in boolean): move all "OperatorXinplace" from expressionGen to AssignmentGen, see if we can get rid of the Result return type.

22
examples/test.p8
View File

@ -10,15 +10,19 @@ main {
ubyte @shared offset=4
uword @shared az = $4000
ubyte @shared value = 22
@($4004) = 99
az[4]--
@(az + offset)--
txt.print_ub(@($4004))
txt.nl()
az[4]++
@(az+offset)++
txt.print_ub(@($4004))
txt.nl()
cx16.r0H = value*4 + az[value]
cx16.r0L = az[value] + value*4
; @($4004) = 99
; az[4]--
; @(az + offset)--
; txt.print_ub(@($4004))
; txt.nl()
; az[4]++
; @(az+offset)++
; txt.print_ub(@($4004))
; txt.nl()
; cx16.r0L = az[4] + value*5
; cx16.r1L = value*5 + az[4]