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improved codegen for for loops downto 0
This commit is contained in:
Irmen de Jong
parent
4a2dcd20d1
commit
699a2bb7ab
@ -60,13 +60,18 @@ internal class ForLoopsAsmGen(
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// pre-check for end already reached
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if(iterableDt==DataType.ARRAY_B) {
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asmgen.out(" sta $modifiedLabel+1")
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if(stepsize<0)
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asmgen.out("""
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clc
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sbc $varname
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bvc +
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eor #${'$'}80
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+ bpl $endLabel""")
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if(stepsize<0) {
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if(range.to.asConstInteger()==0 && asmgen.options.optimize) {
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throw AssemblyError("downto 0 (signed byte) should have been replaced by an until-loop")
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} else {
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asmgen.out("""
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clc
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sbc $varname
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bvc +
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eor #${'$'}80
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+ bpl $endLabel""")
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}
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}
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else
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asmgen.out("""
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sec
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@ -75,12 +80,17 @@ internal class ForLoopsAsmGen(
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eor #${'$'}80
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+ bmi $endLabel""")
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} else {
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if(stepsize<0)
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asmgen.out("""
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cmp $varname
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beq +
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bcs $endLabel
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if(stepsize<0) {
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if(range.to.asConstInteger()==0 && asmgen.options.optimize) {
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throw AssemblyError("downto 0 (unsigned byte) should have been replaced by an until-loop")
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} else {
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asmgen.out("""
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cmp $varname
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beq +
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bcs $endLabel
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+""")
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}
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}
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else
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asmgen.out(" cmp $varname | bcc $endLabel")
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asmgen.out(" sta $modifiedLabel+1")
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@ -160,6 +170,8 @@ $modifiedLabel cmp #0 ; modified
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// words, step 1 or -1
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stepsize == 1 || stepsize == -1 -> {
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if(range.to.asConstInteger()==0 && asmgen.options.optimize)
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throw AssemblyError("downto 0 (words) should have been replaced by an until-loop")
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val varname = asmgen.asmVariableName(stmt.variable)
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assignLoopvarWord(stmt, range)
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asmgen.assignExpressionToRegister(range.to, RegisterOrPair.AY)
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@ -486,7 +498,7 @@ $loopLabel sty $indexVar
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if(iterableDt==DataType.ARRAY_B || iterableDt==DataType.ARRAY_UB) {
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if(range.last==range.first) return translateForSimpleByteRangeAsc(stmt, range)
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if(range.step==1 && range.last>range.first) return translateForSimpleByteRangeAsc(stmt, range)
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if(range.step==-1 && range.last<range.first) return translateForSimpleByteRangeDesc(stmt, range)
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if(range.step==-1 && range.last<range.first) return translateForSimpleByteRangeDesc(stmt, range, iterableDt==DataType.ARRAY_UB)
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}
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else if(iterableDt==DataType.ARRAY_W || iterableDt==DataType.ARRAY_UW) {
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if(range.last==range.first) return translateForSimpleWordRangeAsc(stmt, range)
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@ -632,41 +644,41 @@ $endLabel""")
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asmgen.loopEndLabels.removeLast()
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}
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private fun translateForSimpleByteRangeDesc(stmt: PtForLoop, range: IntProgression) {
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private fun translateForSimpleByteRangeDesc(stmt: PtForLoop, range: IntProgression, unsigned: Boolean) {
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val loopLabel = asmgen.makeLabel("for_loop")
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val endLabel = asmgen.makeLabel("for_end")
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asmgen.loopEndLabels.add(endLabel)
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val varname = asmgen.asmVariableName(stmt.variable)
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asmgen.out("""
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lda #${range.first}
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sta $varname
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lda #${range.first}
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sta $varname
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$loopLabel""")
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asmgen.translate(stmt.statements)
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when (range.last) {
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0 -> {
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asmgen.out("""
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lda $varname
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beq $endLabel
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dec $varname""")
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asmgen.jmp(loopLabel)
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asmgen.out(endLabel)
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if(!unsigned || range.first<=127) {
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asmgen.out("""
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dec $varname
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bpl $loopLabel""")
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} else {
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asmgen.out("""
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dec $varname
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lda $varname
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cmp #255
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bne $loopLabel""")
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}
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}
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1 -> {
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asmgen.out("""
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dec $varname
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bne $loopLabel
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$endLabel""")
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bne $loopLabel""")
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}
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else -> {
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asmgen.out("""
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dec $varname
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lda $varname
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cmp #${range.last-1}
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bne $loopLabel
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$endLabel""")
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bne $loopLabel""")
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}
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}
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asmgen.loopEndLabels.removeLast()
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}
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private fun translateForSimpleWordRangeAsc(stmt: PtForLoop, range: IntProgression) {
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@ -708,13 +720,22 @@ $loopLabel""")
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sty $varname+1
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$loopLabel""")
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asmgen.translate(stmt.statements)
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if(range.last==0) {
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asmgen.out("""
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lda $varname
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bne ++
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lda $varname+1
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beq $endLabel""")
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} else {
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asmgen.out("""
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lda $varname
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cmp #<${range.last}
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bne +
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lda $varname+1
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cmp #>${range.last}
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beq $endLabel""")
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}
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asmgen.out("""
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lda $varname
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cmp #<${range.last}
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bne +
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lda $varname+1
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cmp #>${range.last}
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beq $endLabel
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+ lda $varname
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bne +
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dec $varname+1
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@ -518,6 +518,12 @@ Loops
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-----
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The *for*-loop is used to let a variable iterate over a range of values. Iteration is done in steps of 1, but you can change this.
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.. sidebar::
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Optimization
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Usually a loop in descending order downto 0 or 1, produces more efficient assembly code than the same loop in ascending order.
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The loop variable must be declared separately as byte or word earlier, so that you can reuse it for multiple occasions.
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Iterating with a floating point variable is not supported. If you want to loop over a floating-point array, use a loop with an integer index variable instead.
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If the from value is already outside of the loop range, the whole for loop is skipped.
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@ -1,6 +1,12 @@
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TODO
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====
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improve codegen for for loops downto 0,1 when start value is not const.
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IR: Improve codegen for for loops downto 0. (BPL if <=127 etc like 6502 codegen?)
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Improve register load order in subroutine call args assignments:
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in certain situations, the "wrong" order of evaluation of function call arguments is done which results
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in overwriting registers that already got their value, which requires a lot of stack juggling (especially on plain 6502 cpu!)
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165
examples/test.p8
165
examples/test.p8
@ -5,139 +5,46 @@
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main {
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sub start() {
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ubyte @shared x
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uword @shared w
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bool flag1, flag2
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sys.clear_carry()
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flag1 = onlyCarry()
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if flag1
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txt.print("1: ok\n")
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else
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txt.print("1: fail\n")
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x=1
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flag1 = onlyZero()
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if flag1
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txt.print("2: ok\n")
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else
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txt.print("2: fail\n")
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sys.clear_carry()
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flag1, x = carryAndByte()
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if flag1 and x==42
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txt.print("3: ok\n")
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else
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txt.print("3: fail\n")
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sys.clear_carry()
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flag1, w = carryAndWord()
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if flag1 and w==4242
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txt.print("4: ok\n")
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else
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txt.print("4: fail\n")
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sys.clear_carry()
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flag1, x, w = carryAndValues()
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if flag1 and x==99 and w==9999
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txt.print("5: ok\n")
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else
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txt.print("5: fail\n")
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x = 1
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sys.clear_carry()
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flag1, flag2 = onlyCarryAndZero()
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if flag1 and flag2
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txt.print("6: ok\n")
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else
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txt.print("6: fail\n")
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x = 1
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sys.clear_carry()
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flag1, flag2, x = carryAndZeroAndByte()
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if flag1 and flag2 and x==33
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txt.print("7: ok\n")
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else
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txt.print("7: fail\n")
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x = 1
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sys.clear_carry()
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flag1, flag2, x, w = carryAndNegativeAndByteAndWord()
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if flag1 and flag2 and x==55 and w==51400
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txt.print("8: ok\n")
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else
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txt.print("8: fail\n")
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}
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ubyte x
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uword w
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uword @shared wstart=50000
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ubyte @shared bstart=127
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uword y
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uword duration
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byte b
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asmsub carryAndNegativeAndByteAndWord() -> bool @Pc, bool @Pn, ubyte @X, uword @AY {
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%asm {{
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ldx #55
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lda #200
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ldy #200
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sec
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rts
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}}
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}
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cbm.SETTIM(0,0,0)
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repeat 5000 {
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y=0
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; for x in bstart downto 0 {
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; y++
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; }
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x = bstart
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do {
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y++
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x--
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} until x==255
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}
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txt.print_uw(cbm.RDTIM16())
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if y!=128
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txt.print("error 1\n")
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asmsub carryAndZeroAndByte() -> bool @Pc, bool @Pz, ubyte @Y {
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%asm {{
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ldy #33
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lda #0
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sec
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rts
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}}
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}
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/*
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for w in 65535 downto 0 {
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y++
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}
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if y!=0
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txt.print("error 10\n")
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y=0
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for w in 0 to 65535 {
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y++
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}
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if y!=0
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txt.print("error 11\n")
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*/
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asmsub onlyCarryAndZero() -> bool @Pc, bool @Pz {
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%asm {{
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lda #0
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sec
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rts
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}}
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}
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asmsub carryAndValues() -> bool @Pc, ubyte @X, uword @AY {
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%asm {{
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ldx #99
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lda #<9999
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ldy #>9999
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sec
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rts
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}}
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}
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asmsub carryAndWord() -> bool @Pc, uword @AY {
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%asm {{
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lda #<4242
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ldy #>4242
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sec
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rts
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}}
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}
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asmsub carryAndByte() -> bool @Pc, ubyte @A {
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%asm {{
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lda #42
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sec
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rts
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}}
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}
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asmsub onlyCarry() -> bool @Pc {
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%asm {{
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sec
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rts
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}}
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}
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asmsub onlyZero() -> bool @Pz {
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%asm {{
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lda #0
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rts
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}}
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txt.print("\nall done\n")
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}
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}
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