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optimization of < and >= in expressions

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This commit is contained in:
Irmen de Jong 2023-08-07 02:51:25 +02:00
parent 68a6f99c9f
commit 0d63cdcb96
3 changed files with 83 additions and 45 deletions
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101
codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
View File

@ -1084,6 +1084,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
}
private fun byteLess(expr: PtBinaryExpression, signed: Boolean) {
// note: this is the inverse of byteGreaterEqual
when(expr.right) {
is PtNumber -> {
val number = (expr.right as PtNumber).number.toInt()
@ -1102,7 +1103,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
else
asmgen.out("""
cmp #$number
asl a
rol a
and #1
eor #1""")
}
@ -1128,6 +1129,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
eor #1""")
}
else -> {
// note: left and right operands get reversed here to reduce code size
asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
if(signed)
asmgen.out("""
@ -1137,22 +1139,18 @@ internal class AssignmentAsmGen(private val program: PtProgram,
eor #$80
+ asl a
rol a
and #1
eor #1""")
and #1""")
else
asmgen.out("""
tay
lda #0
cpy P8ZP_SCRATCH_B1
beq +
cmp P8ZP_SCRATCH_B1
rol a
+""")
and #1""")
}
}
}
private fun byteLessEquals(expr: PtBinaryExpression, signed: Boolean) {
// TODO no need to use a temporary variable if the right expression is a literal number or a variable name (or register name)
// TODO optimize: no need to use a temporary variable if the right expression is a literal number or a variable name (or register name)
asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
if(signed)
asmgen.out("""
@ -1173,7 +1171,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
}
private fun byteGreater(expr: PtBinaryExpression, signed: Boolean) {
// TODO no need to use a temporary variable if the right expression is a literal number or a variable name (or register name)
// TODO optimize: no need to use a temporary variable if the right expression is a literal number or a variable name (or register name)
asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
if(signed)
asmgen.out("""
@ -1195,28 +1193,67 @@ internal class AssignmentAsmGen(private val program: PtProgram,
}
private fun byteGreaterEquals(expr: PtBinaryExpression, signed: Boolean) {
// TODO no need to use a temporary variable if the right expression is a literal number or a variable name (or register name)
asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
if(signed)
asmgen.out("""
clc
sbc P8ZP_SCRATCH_B1
bvc +
eor #$80
+ bmi +
lda #0
beq ++
+ lda #1
+""")
else
asmgen.out("""
cmp P8ZP_SCRATCH_B1
beq +
bcc +
lda #0
beq ++
+ lda #1
+""")
// note: this is the inverse of byteLess
when(expr.right) {
is PtNumber -> {
val number = (expr.right as PtNumber).number.toInt()
asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
if(signed) {
asmgen.out("""
sec
sbc #$number
bvs +
eor #$80
+ asl a
rol a
and #1""")
}
else
asmgen.out("""
cmp #$number
rol a
and #1""")
}
is PtIdentifier -> {
val varname = (expr.right as PtIdentifier).name
asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
if(signed) {
asmgen.out("""
sec
sbc $varname
bvs +
eor #$80
+ asl a
rol a
and #1""")
}
else
asmgen.out("""
cmp $varname
rol a
and #1""")
}
else -> {
// note: left and right operands get reversed here to reduce code size
asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
if(signed)
asmgen.out("""
clc
sbc P8ZP_SCRATCH_B1
bvs +
eor #$80
+ asl a
rol a
and #1
eor #1""")
else
asmgen.out("""
cmp P8ZP_SCRATCH_B1
rol a
and #1
eor #1""")
}
}
}
private fun assignOptimizedComparisonWords(expr: PtBinaryExpression, assign: AsmAssignment): Boolean {

3
docs/source/todo.rst
View File

@ -1,7 +1,8 @@
TODO
====
- try to reduce the number of temp variables in comparison expressions like if a>4 or a<2 .... See assignOptimizedComparisonBytes().
- optimize byteLessEquals() and byteGreater() in AssignmentAsmGen.
- in other codegen for comparisons, try to reduce lda #0/lda #1 by rol a using the carry from the cmp if possible.
- investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
- IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction

24
examples/test.p8
View File

@ -3,28 +3,28 @@
main {
sub start() {
ubyte a = 1
ubyte var1 = 2
ubyte var2 = 4
ubyte a = 2
ubyte var1 = 3
ubyte var2 = 1
if a==1 and a<4 {
if a==2 and a>=1 {
a++
}
if a==var1 and a<var2 {
if a==var1 and a>=var2 {
a++
}
txt.print_ub(a) ; 3
txt.print_ub(a) ; 4
byte sa = 1
byte svar1 = 2
byte svar2 = 4
byte sa = 2
byte svar1 = 3
byte svar2 = 1
if sa==1 and sa<4 {
if sa==2 and sa>=1 {
sa++
}
if sa==svar1 and sa<svar2 {
if sa==svar1 and sa>=svar2 {
sa++
}
txt.print_b(sa) ; 3 code 287
txt.print_b(sa) ; 4 code 287
}
}