From 2668bf8519f5e590316bf5f657cf1e6da1d82441 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 9 Dec 2023 21:48:22 +0100
Subject: [PATCH] fix void optimization issue

---
 .../src/prog8/optimizer/UnusedCodeRemover.kt  | 21 ++++++---
 docs/source/todo.rst                          | 10 -----
 examples/test.p8                              | 45 ++++++++++++++++---
 3 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt b/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
index 66f52ef16..81418df0b 100644
--- a/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
+++ b/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
@@ -139,13 +139,20 @@ class UnusedCodeRemover(private val program: Program,
                                     )
                                 } else if(assignment.value is IFunctionCall) {
                                     // replace the unused variable's initializer function call by a void
-                                    errors.warn("replaced unused variable '${decl.name}' with void call, maybe this can be removed altogether", decl.position)
-                                    val fcall = assignment.value as IFunctionCall
-                                    val voidCall = FunctionCallStatement(fcall.target, fcall.args, true, fcall.position)
-                                    return listOf(
-                                        IAstModification.ReplaceNode(decl, voidCall, parent),
-                                        IAstModification.Remove(assignment, assignment.parent as IStatementContainer)
-                                    )
+                                    // but only if the vardecl immediately precedes it!
+                                    if(singleUse.parent.parent === parent) {
+                                        val declIndex = (parent as IStatementContainer).statements.indexOf(decl)
+                                        val singleUseIndex = (parent as IStatementContainer).statements.indexOf(singleUse.parent)
+                                        if(declIndex==singleUseIndex-1) {
+                                            errors.warn("replaced unused variable '${decl.name}' with void call, maybe this can be removed altogether", decl.position)
+                                            val fcall = assignment.value as IFunctionCall
+                                            val voidCall = FunctionCallStatement(fcall.target, fcall.args, true, fcall.position)
+                                            return listOf(
+                                                IAstModification.ReplaceNode(decl, voidCall, parent),
+                                                IAstModification.Remove(assignment, assignment.parent as IStatementContainer)
+                                            )
+                                        }
+                                    }
                                 } else {
                                     errors.warn("variable '${decl.name}' is unused but has non-trivial initialization assignment. Leaving this in but maybe it can be removed altogether", decl.position)
                                 }
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 95abbeda6..2f8247868 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -2,16 +2,6 @@
 TODO
 ====
 
-
-- fix problem with conversion to void call messing up the return '!':
-            if cx16.r0L==9 {
-                ; process TAB
-                uword cmd = grab_cmdline()
-                return '!'
-            }
-
-
-
 - [on branch: shortcircuit] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
 
 ...
diff --git a/examples/test.p8 b/examples/test.p8
index 881129f80..705953b6e 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,9 +1,44 @@
-%option enable_floats
+%import textio
+%import string
+%zeropage basicsafe
+
 main {
     sub start() {
-        uword w1 = 000_1234_5__
-        uword w2 = $ff_ee
-        uword w3 = %11_0000_111111__0000
-        float fl = 3_000_001.141_592_654
+        cx16.set_chrin_keyhandler(0, &keystroke_handler)
+        cbm.CHRIN()
+    }
+
+    sub keystroke_handler() -> ubyte {
+        %asm {{
+            sta  cx16.r0L
+        }}
+        uword cmdxx = grab_cmdline()
+        if_cs {
+            ; first entry, decide if we want to override
+            if cx16.r0L==9 {
+                ; intercept TAB
+                sys.clear_carry()
+                return 0
+            }
+            sys.set_carry()
+            return 0
+        } else {
+            if cx16.r0L==9 {
+                %asm {{
+                    brk ; BOOM
+                }}
+                uword cmd = grab_cmdline()
+                if cmd and cmd[0] {
+                    ;cx16.r5++
+                }
+                return '!'
+            }
+            return 0    ; eat all other characters
+        }
+
+        sub grab_cmdline() -> uword {
+            cx16.r9++
+            return $5000
+        }
     }
 }