From 97b9c8f320a60a35a3537658e9b00e146995421c Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 12 Sep 2020 18:53:44 +0200
Subject: [PATCH] don't clobber A when trying to save X at functioncall

---
 .../compiler/target/c64/codegen/AsmGen.kt     | 51 ++++++++++---------
 .../target/c64/codegen/FunctionCallAsmGen.kt  |  4 +-
 examples/tehtriz.p8                           |  1 -
 examples/test.p8                              |  3 +-
 4 files changed, 31 insertions(+), 28 deletions(-)

diff --git a/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
index c126be98c..8d91cd64b 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
@@ -552,55 +552,60 @@ internal class AsmGen(private val program: Program,
 
     internal fun fixNameSymbols(name: String) = name.replace("<", "prog8_").replace(">", "")     // take care of the autogenerated invalid (anon) label names
 
-    internal fun saveRegister(register: CpuRegister, forFuncCall: Boolean = false, dontClobberA: Boolean = false) {
+
+    private val saveRegisterLabels = Stack<String>();
+
+    internal fun saveRegister(register: CpuRegister, forFuncCall: Boolean = false) {
         when(register) {
             CpuRegister.A -> out("  pha")
             CpuRegister.X -> {
-                // TODO get rid of REG_X altogheter! replace with sta _save | txa | pha | lda _save
+                // TODO get rid of REG_X altogether!
                 when {
                     CompilationTarget.instance.machine.cpu == CpuType.CPU65c02 -> out("  phx")
                     forFuncCall -> {
-                        if(dontClobberA)
-                            out("  sta  P8ZP_SCRATCH_REG |  txa |  pha |  lda  P8ZP_SCRATCH_REG")
-                        else
-                            out("  txa |  pha")
+                        val save = makeLabel("saveX")
+                        saveRegisterLabels.push(save)
+                        out("""
+                            stx  $save
+                            jmp  +
+$save      .byte 0
++""")
                     }
                     else -> out("  stx  P8ZP_SCRATCH_REG_X")
                 }
             }
             CpuRegister.Y -> {
-                when {
-                    CompilationTarget.instance.machine.cpu == CpuType.CPU65c02 -> out("  phy")
-                    dontClobberA -> out("  sta  P8ZP_SCRATCH_REG |  tya |  pha |  lda  P8ZP_SCRATCH_REG")
-                    else -> out("  tya | pha")
+                if (CompilationTarget.instance.machine.cpu == CpuType.CPU65c02) out("  phy")
+                else {
+                    val save = makeLabel("saveY")
+                    out("""
+                            sty  $save
+                            jmp  +
+$save      .byte 0
++""")
                 }
             }
         }
     }
 
-    internal fun restoreRegister(register: CpuRegister, forFuncCall: Boolean = false, dontClobberA: Boolean=false) {
+    internal fun restoreRegister(register: CpuRegister, forFuncCall: Boolean = false) {
         when(register) {
-            CpuRegister.A -> {
-                require(!dontClobberA)
-                out("  pla")
-            }
+            CpuRegister.A -> out("  pla")
             CpuRegister.X -> {
                 when {
                     CompilationTarget.instance.machine.cpu == CpuType.CPU65c02 -> out("  plx")
                     forFuncCall -> {
-                        if(dontClobberA)
-                            out("  sta  P8ZP_SCRATCH_REG |  pla |  tax |  lda  P8ZP_SCRATCH_REG")
-                        else
-                            out("  pla |  tax")
+                        val save = saveRegisterLabels.pop()
+                        out("  ldx  $save")
                     }
                     else -> out("  ldx  P8ZP_SCRATCH_REG_X")
                 }
             }
             CpuRegister.Y -> {
-                when {
-                    CompilationTarget.instance.machine.cpu == CpuType.CPU65c02 -> out("  ply")
-                    dontClobberA -> out("  sta  P8ZP_SCRATCH_REG |  pla |  tay |  lda  P8ZP_SCRATCH_REG")
-                    else -> out("  pla | tay")
+                if (CompilationTarget.instance.machine.cpu == CpuType.CPU65c02) out("  ply")
+                else {
+                    val save = saveRegisterLabels.pop()
+                    out("  ldy  $save")
                 }
             }
         }
diff --git a/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
index 2227c0fe5..84afb5af7 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
@@ -19,7 +19,7 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
         val sub = stmt.target.targetSubroutine(program.namespace) ?: throw AssemblyError("undefined subroutine ${stmt.target}")
         val saveX = CpuRegister.X in sub.asmClobbers || sub.regXasResult() || sub.regXasParam()
         if(saveX)
-            asmgen.saveRegister(CpuRegister.X, forFuncCall = true, dontClobberA = false)  // we only save X for now (required! is the eval stack pointer), screw A and Y...
+            asmgen.saveRegister(CpuRegister.X, forFuncCall = true)
 
         val subName = asmgen.asmSymbolName(stmt.target)
         if(stmt.args.isNotEmpty()) {
@@ -58,7 +58,7 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
         asmgen.out("  jsr  $subName")
 
         if(saveX)
-            asmgen.restoreRegister(CpuRegister.X, forFuncCall = true, dontClobberA = false)
+            asmgen.restoreRegister(CpuRegister.X, forFuncCall = true)
     }
 
     private fun registerArgsViaStackEvaluation(stmt: IFunctionCall, sub: Subroutine) {
diff --git a/examples/tehtriz.p8 b/examples/tehtriz.p8
index b00edf84d..bb225a9ae 100644
--- a/examples/tehtriz.p8
+++ b/examples/tehtriz.p8
@@ -248,7 +248,6 @@ waitkey:
         c64.CHROUT('K')
 
         while c64.GETIN()!=133 {
-            ; TODO FIX THIS, DOESN'T TRIGGER ANYMORE ON F1
             ; endless loop until user presses F1 to restart the game
         }
     }
diff --git a/examples/test.p8 b/examples/test.p8
index db8039cfc..a25869b83 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,5 +1,4 @@
-%target cx16
-%import cx16textio
+%import c64textio
 ;%import c64flt
 ;%option enable_floats
 ; %zeropage kernalsafe