From 68a6f99c9fb8796d2cceffde0f41649f6dd7b015 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Mon, 7 Aug 2023 01:49:00 +0200
Subject: [PATCH] optimization of < in expressions

---
 .../cpu6502/assignment/AssignmentAsmGen.kt    | 78 +++++++++++++------
 examples/test.p8                              | 24 +++---
 2 files changed, 71 insertions(+), 31 deletions(-)

diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
index 2fed282ec..cb91d8cd0 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
@@ -996,8 +996,8 @@ internal class AssignmentAsmGen(private val program: PtProgram,
     private fun assignOptimizedComparisonBytes(expr: PtBinaryExpression, assign: AsmAssignment): Boolean {
         val signed = expr.left.type == DataType.BYTE || expr.right.type ==  DataType.BYTE
         when(expr.operator) {
-            "==" -> byteEquals(expr, signed)
-            "!=" -> byteNotEquals(expr, signed)
+            "==" -> byteEquals(expr)
+            "!=" -> byteNotEquals(expr)
             "<" -> byteLess(expr, signed)
             "<=" -> byteLessEquals(expr, signed)
             ">" -> byteGreater(expr, signed)
@@ -1005,15 +1005,15 @@ internal class AssignmentAsmGen(private val program: PtProgram,
             else -> return false
         }
 
-        assignRegisterByte(assign.target, CpuRegister.A, signed)
+        assignRegisterByte(assign.target, CpuRegister.A, false)
         return true
     }
 
-    private fun byteEquals(expr: PtBinaryExpression, signed: Boolean) {
+    private fun byteEquals(expr: PtBinaryExpression) {
         when (expr.right) {
             is PtNumber -> {
                 val number = (expr.right as PtNumber).number.toInt()
-                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
+                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A)
                 asmgen.out("""
                     cmp  #$number
                     beq  +
@@ -1024,7 +1024,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
             }
             is PtIdentifier -> {
                 val varname = (expr.right as PtIdentifier).name
-                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
+                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A)
                 asmgen.out("""
                     cmp  $varname
                     beq  +
@@ -1046,11 +1046,11 @@ internal class AssignmentAsmGen(private val program: PtProgram,
         }
     }
 
-    private fun byteNotEquals(expr: PtBinaryExpression, signed: Boolean) {
+    private fun byteNotEquals(expr: PtBinaryExpression) {
         when(expr.right) {
             is PtNumber -> {
                 val number = (expr.right as PtNumber).number.toInt()
-                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
+                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A)
                 asmgen.out("""
                     cmp  #$number
                     bne  +
@@ -1061,7 +1061,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
             }
             is PtIdentifier -> {
                 val varname = (expr.right as PtIdentifier).name
-                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A, signed)
+                asmgen.assignExpressionToRegister(expr.left, RegisterOrPair.A)
                 asmgen.out("""
                     cmp  $varname
                     bne  +
@@ -1084,27 +1084,61 @@ internal class AssignmentAsmGen(private val program: PtProgram,
     }
 
     private fun byteLess(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)
         when(expr.right) {
-//            is PtNumber -> {
-//                TODO("< number")
-//            }
-//            is PtIdentifier -> {
-//                TODO("< variable")
-//            }
+            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  #$80
++                       asl  a
+                        rol  a
+                        and  #1
+                        eor  #1""")
+                }
+                else
+                    asmgen.out("""
+                        cmp  #$number
+                        asl  a
+                        and  #1
+                        eor  #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
+                        eor  #1""")
+                }
+                else
+                    asmgen.out("""
+                        cmp  $varname
+                        rol  a
+                        and  #1
+                        eor  #1""")
+            }
             else -> {
                 asmgen.assignByteOperandsToAAndVar(expr.right, expr.left, "P8ZP_SCRATCH_B1")
                 if(signed)
                     asmgen.out("""
                         clc
                         sbc  P8ZP_SCRATCH_B1
-                        bvc  +
+                        bvs  +
                         eor  #$80
-+                       bpl  +
-                        lda  #0
-                        beq  ++
-+                       lda  #1                        
-+""")
++                       asl  a
+                        rol  a
+                        and  #1
+                        eor  #1""")
                 else
                     asmgen.out("""
                         tay
diff --git a/examples/test.p8 b/examples/test.p8
index b1526b5ac..7d2164f19 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,21 +4,27 @@
 main {
     sub start() {
         ubyte a = 1
-        ubyte var1 = 1
+        ubyte var1 = 2
         ubyte var2 = 4
 
+        if a==1 and a<4 {
+            a++
+        }
         if a==var1 and a<var2 {
             a++
         }
-        txt.print_ub(a)  ; 2        code 1e8
+        txt.print_ub(a)  ; 3
 
-;        if a>4 or a<2 {
-;            a++
-;        }
-;
-;        if a>=2 and a<4 {
-;            a++
-;        }
+        byte sa = 1
+        byte svar1 = 2
+        byte svar2 = 4
 
+        if sa==1 and sa<4 {
+            sa++
+        }
+        if sa==svar1 and sa<svar2 {
+            sa++
+        }
+        txt.print_b(sa)  ; 3        code 287
     }
 }