From 225bfc4164e88aa281bc88bc04416ee8dc7857d9 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Fri, 25 Sep 2020 22:51:59 +0200
Subject: [PATCH] fix 16+8 bit add and sub sign extensions

---
 .../assignment/AugmentableAssignmentAsmGen.kt | 70 +++++++++++++------
 examples/testforloops.p8                      |  2 -
 2 files changed, 47 insertions(+), 25 deletions(-)

diff --git a/compiler/src/prog8/compiler/target/c64/codegen/assignment/AugmentableAssignmentAsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/assignment/AugmentableAssignmentAsmGen.kt
index d23e1c614..e865e2586 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/assignment/AugmentableAssignmentAsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/assignment/AugmentableAssignmentAsmGen.kt
@@ -840,22 +840,34 @@ internal class AugmentableAssignmentAsmGen(private val program: Program,
                 // the other variable is a BYTE type so optimize for that
                 when (operator) {
                     // note: ** (power) operator requires floats.
-                    "+" -> asmgen.out("""
-                        lda  $name
-                        clc
-                        adc  $otherName
+                    "+" -> {
+                        asmgen.out("""
+                        ldy  #0
+                        lda  $otherName
+                        bpl  +
+                        dey     ; sign extend
++                       clc
+                        adc  $name
                         sta  $name
-                        bcc  +
-                        inc  $name+1
-+                           """)
-                    "-" -> asmgen.out("""
+                        tya
+                        adc  $name+1
+                        sta  $name+1""")
+                    }
+                    "-" -> {
+                        asmgen.out("""
+                        ldy  #0
+                        lda  $otherName
+                        bpl  +
+                        dey     ; sign extend
++                       sty  P8ZP_SCRATCH_B1
                         lda  $name
                         sec
                         sbc  $otherName
                         sta  $name
-                        bcs  +
-                        dec  $name+1
-+                           """)
+                        lda  $name+1
+                        sbc  P8ZP_SCRATCH_B1
+                        sta  $name+1""")
+                    }
                     "*" -> {
                         asmgen.out("""
                             lda  $otherName
@@ -993,25 +1005,37 @@ internal class AugmentableAssignmentAsmGen(private val program: Program,
 
         when(valueDt) {
             in ByteDatatypes -> {
-                // the other variable is a BYTE type so optimize for that   TODO does this even occur?
+                // the other variable is a BYTE type so optimize for that
                 when (operator) {
                     // note: ** (power) operator requires floats.
-                    "+" -> asmgen.out("""
-                        lda  $name
-                        clc
-                        adc  P8ESTACK_LO+1,x
+                    "+" -> {
+                        asmgen.out("""
+                        ldy  #0
+                        lda  P8ESTACK_LO+1,x
+                        bpl  +
+                        dey         ; sign extend
++                       clc
+                        adc  $name
                         sta  $name
-                        bcc  +
-                        inc  $name+1
-+                           """)
-                    "-" -> asmgen.out("""
+                        tya
+                        adc  $name+1
+                        sta  $name+1""")
+                    }
+                    "-" -> {
+                        asmgen.out("""
+                        ldy  #0
+                        lda  P8ESTACK_LO+1,x
+                        bpl  +
+                        dey         ; sign extend
++                       sty  P8ZP_SCRATCH_B1
                         lda  $name
                         sec
                         sbc  P8ESTACK_LO+1,x
                         sta  $name
-                        bcs  +
-                        dec  $name+1
-+                           """)
+                        lda  $name+1
+                        sbc  P8ZP_SCRATCH_B1
+                        sta  $name+1""")
+                    }
                     "*" -> TODO("mul word byte")
                     "/" -> TODO("div word byte")
                     "%" -> TODO("word remainder byte")
diff --git a/examples/testforloops.p8 b/examples/testforloops.p8
index e48789946..0d907a13a 100644
--- a/examples/testforloops.p8
+++ b/examples/testforloops.p8
@@ -3,8 +3,6 @@
 
 ; Note: this program is compatible with C64 and CX16.
 
-; TODO fix byte var in arrayvar fail
-
 main {
 
     sub start() {