use var initializer assignments in a clearer way

codeGeneration/src/prog8/codegen/target/cpu6502/codegen/AsmGen.kt

@@ -220,11 +220,7 @@ class AsmGen(private val program: Program,
         if(options.dontReinitGlobals) {
             block.statements.asSequence().filterIsInstance<VarDecl>().forEach {
                 it.zeropage = ZeropageWish.NOT_IN_ZEROPAGE
-                val init = it.nextSibling() as? Assignment
-                if(init?.target?.identifier?.targetVarDecl(program) === it) {
-                    // put the init value back into the vardecl
-                    it.value = init.value
-                }
+                it.findInitializer(program)?.let { initializer -> it.value = initializer.value }    // put the init value back into the vardecl
             }
         }
 

compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt

@@ -85,4 +85,16 @@ class AstPreprocessor(val program: Program, val errors: IErrorReporter) : AstWal
         }
         return noModifications
     }
+
+    override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
+        val nextAssignment = decl.nextSibling() as? Assignment
+        if(nextAssignment!=null && nextAssignment.origin!=AssignmentOrigin.VARINIT) {
+            // check if it's a proper initializer assignment for the variable
+            if(decl.value==null && nextAssignment.target.identifier?.targetVarDecl(program)===decl) {
+                if(!nextAssignment.value.referencesIdentifier(nextAssignment.target.identifier!!.nameInSource))
+                    nextAssignment.origin = AssignmentOrigin.VARINIT
+            }
+        }
+        return noModifications
+    }
 }

compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt

@@ -58,16 +58,9 @@ internal class StatementReorderer(val program: Program,
                             // no need to zero out the special internal returnvalue intermediates.
                             return noModifications
                         }
-                        val nextStmt  = decl.nextSibling()
-                        val nextAssign = nextStmt as? Assignment
-                        if(nextAssign!=null && !nextAssign.isAugmentable) {
-                            val target = nextAssign.target.identifier?.targetStatement(program)
-                            if(target === decl) {
-                                // an initializer assignment for a vardecl is already here
-                                return noModifications
-                            }
-                        }
-                        val nextFor = nextStmt as? ForLoop
+                        if(decl.findInitializer(program)!=null)
+                            return noModifications   // an initializer assignment for a vardecl is already here
+                        val nextFor = decl.nextSibling() as? ForLoop
                         val hasNextForWithThisLoopvar = nextFor?.loopVar?.nameInSource==listOf(decl.name)
                         if (!hasNextForWithThisLoopvar) {
                             // Add assignment to initialize with zero

compiler/test/TestCompilerOnCharLit.kt

@@ -10,7 +10,6 @@ import prog8.ast.base.DataType
 import prog8.ast.base.VarDeclType
 import prog8.ast.expressions.IdentifierReference
 import prog8.ast.expressions.NumericLiteralValue
-import prog8.ast.statements.Assignment
 import prog8.codegen.target.Cx16Target
 import prog8tests.helpers.assertSuccess
 import prog8tests.helpers.compileText
@@ -76,7 +75,7 @@ class TestCompilerOnCharLit: FunSpec({
         withClue("initializer value should have been moved to separate assignment"){
             decl.value shouldBe null
         }
-        val assignInitialValue = decl.nextSibling() as Assignment
+        val assignInitialValue = decl.findInitializer(program)!!
         assignInitialValue.target.identifier!!.nameInSource shouldBe listOf("ch")
         withClue("char literal should have been replaced by ubyte literal") {
             assignInitialValue.value shouldBe instanceOf<NumericLiteralValue>()

compiler/test/TestOptimization.kt

@@ -604,24 +604,26 @@ class TestOptimization: FunSpec({
                 uword @shared zz
                 zz += 60            ; NOT ok to remove initializer, should evaluate to 60
                 ubyte @shared xx
-                xx = 6+sin8u(xx)     ; NOT ok to remove initializer
+                xx = 6+sin8u(xx)     ; is not an initializer because it references xx
             }
         }
         """
         val result = compileText(C64Target, optimize=true, src, writeAssembly=false).assertSuccess()
+        printProgram(result.program)
         /* expected result:
         uword yy
         yy = 20
         uword zz
         zz = 60
         ubyte xx
+        xx = 0
         xx = sin8u(xx)
         xx += 6
          */
         val stmts = result.program.entrypoint.statements
-        stmts.size shouldBe 7
+        stmts.size shouldBe 8
         stmts.filterIsInstance<VarDecl>().size shouldBe 3
-        stmts.filterIsInstance<Assignment>().size shouldBe 4
+        stmts.filterIsInstance<Assignment>().size shouldBe 5
     }
 
     test("only substitue assignments with 0 after a =0 initializer if it is the same variable") {

compilerAst/src/prog8/ast/statements/AstStatements.kt

@@ -272,6 +272,12 @@ class VarDecl(val type: VarDeclType,
         copy.allowInitializeWithZero = this.allowInitializeWithZero
         return copy
     }
+
+    fun findInitializer(program: Program): Assignment? =
+        (parent as IStatementContainer).statements
+        .asSequence()
+        .filterIsInstance<Assignment>()
+        .singleOrNull { it.origin==AssignmentOrigin.VARINIT && it.target.identifier?.targetVarDecl(program) === this }
 }
 
 class ArrayIndex(var indexExpr: Expression,
@@ -399,6 +405,12 @@ class Assignment(var target: AssignTarget, var value: Expression, var origin: As
 
             return false
         }
+
+    fun initializerFor(program: Program) =
+            if(origin==AssignmentOrigin.VARINIT)
+                target.identifier!!.targetVarDecl(program)
+            else
+                null
 }
 
 data class AssignTarget(var identifier: IdentifierReference?,

docs/source/todo.rst

@@ -3,7 +3,6 @@ TODO
 
 For next compiler release (7.7)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- use the assignment origin? in codegen? (origin VARINIT)
 - optimize codegen of pipe operator to avoid needless assigns to temp var