From 9ea69c07b8d3c853da42a7ef2241f82eb8b6b602 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 14 Oct 2023 07:18:37 +0200
Subject: [PATCH] optimize word array reads with indexvar

---
 .../cpu6502/assignment/AssignmentAsmGen.kt    | 11 ++---
 docs/source/todo.rst                          |  8 +---
 examples/test.p8                              | 41 +++++++++++++------
 3 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
index ce3743ebf..f2ed04c63 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt
@@ -88,8 +88,8 @@ internal class AssignmentAsmGen(private val program: PtProgram,
                         assignRegisterpairWord(assign.target, RegisterOrPair.AY)
                     } else {
                         asmgen.loadScaledArrayIndexIntoRegister(value, elementDt, CpuRegister.Y)
-                        asmgen.out("  lda  ${arrayVarName}_lsb,y |  tax |  lda  ${arrayVarName}_msb,y |  tay |  txa")
-                        assignRegisterpairWord(assign.target, RegisterOrPair.AY)
+                        asmgen.out("  lda  ${arrayVarName}_lsb,y |  ldx  ${arrayVarName}_msb,y")
+                        assignRegisterpairWord(assign.target, RegisterOrPair.AX)
                     }
                     return
                 }
@@ -122,8 +122,8 @@ internal class AssignmentAsmGen(private val program: PtProgram,
                         }
                         in WordDatatypes  -> {
                             asmgen.loadScaledArrayIndexIntoRegister(value, elementDt, CpuRegister.Y)
-                            asmgen.out("  lda  $arrayVarName,y |  tax |  lda  $arrayVarName+1,y |  tay |  txa")
-                            assignRegisterpairWord(assign.target, RegisterOrPair.AY)
+                            asmgen.out("  lda  $arrayVarName,y |  ldx  $arrayVarName+1,y")
+                            assignRegisterpairWord(assign.target, RegisterOrPair.AX)
                         }
                         DataType.FLOAT -> {
                             asmgen.loadScaledArrayIndexIntoRegister(value, elementDt, CpuRegister.A)
@@ -2209,7 +2209,8 @@ internal class AssignmentAsmGen(private val program: PtProgram,
                 else
                     program.memsizer.memorySize(arrayDt!!, constIndex)  // add arrayIndexExpr * elementsize  to the address of the array variable.
             } else {
-                TODO("address-of array element $sourceName with non-const index at ${target.position}")
+                val eltSize = program.memsizer.memorySize(ArrayToElementTypes.getValue(arrayDt!!))
+                TODO("address-of array element $sourceName size $eltSize with non-const index at ${target.position}")
             }
         } else 0
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index cf9de7f04..31ed498a3 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -1,13 +1,7 @@
 TODO
 ====
 
-- optimize word array assignment to not use tax/tay etc but simply lda+ldx:  (note: with and without @split!)
-        uword pstep = w_array[index] ->
-            ldy  p8_index
-            lda  p8_w_array,y
-            ldx  p8_w_array+1,y
-            sta  p8_pstep
-            stx  p8_pstep+1
+- fix TODO  "address-of array element" in assignAddressOf()
 
 - gfx2: use vera auto in/decrement in the flood fill routine
 
diff --git a/examples/test.p8 b/examples/test.p8
index 108a3a747..8d3b96799 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,18 +1,33 @@
+%import textio
+%zeropage basicsafe
+
 main {
     sub start() {
-        cx16.r1H = %00000001        ; enable auto-indent
-        cx16.r2L = 4
-        cx16.r2H = 80
-        cx16.r3L = 8
-        cx16.r3H = 11<<4 | 7;  background_color<<4 | text_color
-        cx16.r4 = 0
-        cx16.r1L = 0
-        cx16.rombank($d)
-        %asm {{
-            ldx #2
-            ldy #64
-            jmp $c006
-        }}
+        uword[] w_array = [1111,2222,3333,4444]
+        uword[] @split split_array = [1111,2222,3333,4444]
+        ubyte index = 2
+
+        uword value = 9999
+        w_array[index] = value
+        split_array[index] = value
+
+        uword pstep = w_array[index]
+        uword psteps = split_array[index]
+        ;; uword @zp ptr = &w_array[index]
+
+        txt.print_uw(pstep)
+        txt.nl()
+        txt.print_uw(psteps)
+        txt.nl()
+;        txt.print_uw(peekw(ptr))
+;        txt.nl()
+
+        w_array[index] += 10
+        split_array[index] += 10
+        txt.print_uw(w_array[index])
+        txt.nl()
+        txt.print_uw(split_array[index])
+        txt.nl()
     }
 }