From 4aba0c740543114b196b2cb2a7301b97ec43428f Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Thu, 29 Apr 2021 00:48:16 +0200
Subject: [PATCH] unused variables are removed more aggressively (no longer
 checking asm blocks for their names)

---
 compiler/src/prog8/compiler/Compiler.kt           |  2 +-
 compiler/src/prog8/optimizer/CallGraph.kt         |  2 +-
 compiler/src/prog8/optimizer/UnusedCodeRemover.kt | 14 ++++++++------
 docs/source/todo.rst                              |  1 -
 examples/test.p8                                  |  6 ------
 5 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/compiler/src/prog8/compiler/Compiler.kt b/compiler/src/prog8/compiler/Compiler.kt
index 8aa9275ae..d133dc3d7 100644
--- a/compiler/src/prog8/compiler/Compiler.kt
+++ b/compiler/src/prog8/compiler/Compiler.kt
@@ -317,7 +317,7 @@ private fun writeAssembly(programAst: Program,
     programAst.processAstBeforeAsmGeneration(errors, compilerOptions.compTarget)
     errors.report()
 
-    printAst(programAst)
+    // printAst(programAst)
 
     compilerOptions.compTarget.machine.initializeZeropage(compilerOptions)
     val assembly = asmGeneratorFor(compilerOptions.compTarget,
diff --git a/compiler/src/prog8/optimizer/CallGraph.kt b/compiler/src/prog8/optimizer/CallGraph.kt
index 1e670a104..58b71c242 100644
--- a/compiler/src/prog8/optimizer/CallGraph.kt
+++ b/compiler/src/prog8/optimizer/CallGraph.kt
@@ -182,7 +182,7 @@ class CallGraph(private val program: Program) : IAstVisitor {
             return false
 
         val allReferencedVardecls = allIdentifiersAndTargets.filter { it.value is VarDecl }.map { it.value }.toSet()
-        return decl !in allReferencedVardecls && !nameInAssemblyCode(decl.name)
+        return decl !in allReferencedVardecls // Don't check assembly just for occurrences of variables, if they're not used in prog8 itself, just kill them
     }
 
     private fun nameInAssemblyCode(name: String) = allAssemblyNodes.any { it.assembly.contains(name) }
diff --git a/compiler/src/prog8/optimizer/UnusedCodeRemover.kt b/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
index 8a365cbb5..bee3d85bc 100644
--- a/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
+++ b/compiler/src/prog8/optimizer/UnusedCodeRemover.kt
@@ -104,12 +104,14 @@ internal class UnusedCodeRemover(private val program: Program,
     }
 
     override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
-        val forceOutput = "force_output" in decl.definingBlock().options()
-        if(!forceOutput && !decl.autogeneratedDontRemove && callgraph.unused(decl)) {
-            if(decl.type == VarDeclType.VAR && !decl.definingBlock().isInLibrary)
-                errors.warn("removing unused variable '${decl.name}'", decl.position)
-
-            return listOf(IAstModification.Remove(decl, decl.definingScope()))
+        if(decl.type==VarDeclType.VAR) {
+            val forceOutput = "force_output" in decl.definingBlock().options()
+            if (!forceOutput && !decl.autogeneratedDontRemove && !decl.definingBlock().isInLibrary) {
+                if (callgraph.unused(decl)) {
+                    errors.warn("removing unused variable '${decl.name}'", decl.position)
+                    return listOf(IAstModification.Remove(decl, decl.definingScope()))
+                }
+            }
         }
 
         return noModifications
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 95b87878f..42e9f395a 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -2,7 +2,6 @@
 TODO
 ====
 
-- fix problem that unused vars are no longer properly removed
 - BeforeAsmGenerationAstChanger no longer needs to move vardecls??
 
 - simplify cx16.joystick_get2() once this cx16 rom issue is resolved: https://github.com/commanderx16/x16-rom/issues/203
diff --git a/examples/test.p8 b/examples/test.p8
index 223d2415e..55b2e47c5 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -3,12 +3,6 @@ main {
 
     sub start() {
 
-        ; TODO WHY AREN'T UNUSED VARS REMOVED ANY LONGER???
-
-        ubyte xx1
-        ubyte yy1=22
-        ubyte zz1=33
-
         repeat {
             ubyte xx
             ubyte yy=xx