added @shared flag to vardecl to mark variable as shared with assembly code elsewhere, to not have it optimized away

compiler/src/prog8/optimizer/CallGraph.kt

@@ -174,7 +174,7 @@ class CallGraph(private val program: Program) : IAstVisitor {
     }
 
     fun unused(decl: VarDecl): Boolean {
-        if(decl.type!=VarDeclType.VAR || decl.autogeneratedDontRemove)
+        if(decl.type!=VarDeclType.VAR || decl.autogeneratedDontRemove || decl.sharedWithAsm)
             return false
 
         if(decl.definingBlock() !in usedBlocks)

compiler/src/prog8/optimizer/StatementOptimizer.kt

@@ -30,6 +30,7 @@ internal class StatementOptimizer(private val program: Program,
             val decl = VarDecl(VarDeclType.VAR, returnvar.second, ZeropageWish.DONTCARE, null, retvarName, null,
                 isArray = false,
                 autogeneratedDontRemove = true,
+                sharedWithAsm = false,
                 position = returnvar.third
             )
             returnvar.first.statements.add(0, decl)

compiler/src/prog8/optimizer/UnusedCodeRemover.kt

@@ -103,7 +103,7 @@ internal class UnusedCodeRemover(private val program: Program,
     override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
         if(decl.type==VarDeclType.VAR) {
             val forceOutput = "force_output" in decl.definingBlock().options()
-            if (!forceOutput && !decl.autogeneratedDontRemove && !decl.definingBlock().isInLibrary) {
+            if (!forceOutput && !decl.autogeneratedDontRemove && !decl.sharedWithAsm && !decl.definingBlock().isInLibrary) {
                 if (callgraph.unused(decl)) {
                     errors.warn("removing unused variable '${decl.name}'", decl.position)
                     return listOf(IAstModification.Remove(decl, decl.definingScope()))

compiler/test/UnitTests.kt

@@ -502,7 +502,7 @@ class TestMemory {
 
     @Test
     private fun createTestProgramForMemoryRefViaVar(address: Int, vartype: VarDeclType): AssignTarget {
-        val decl = VarDecl(vartype, DataType.BYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, Position.DUMMY)
+        val decl = VarDecl(vartype, DataType.BYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, false, Position.DUMMY)
         val memexpr = IdentifierReference(listOf("address"), Position.DUMMY)
         val target = AssignTarget(null, null, DirectMemoryWrite(memexpr, Position.DUMMY), Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
@@ -522,7 +522,7 @@ class TestMemory {
 
     @Test
     fun testInValidRamC64_variable() {
-        val decl = VarDecl(VarDeclType.VAR, DataType.BYTE, ZeropageWish.DONTCARE, null, "address", null, false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.VAR, DataType.BYTE, ZeropageWish.DONTCARE, null, "address", null, false, false, false, Position.DUMMY)
         val target = AssignTarget(IdentifierReference(listOf("address"), Position.DUMMY), null, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
         val subroutine = Subroutine("test", emptyList(), emptyList(), emptyList(), emptyList(), emptySet(), null, false, false, mutableListOf(decl, assignment), Position.DUMMY)
@@ -535,7 +535,7 @@ class TestMemory {
     @Test
     fun testInValidRamC64_memmap_variable() {
         val address = 0x1000
-        val decl = VarDecl(VarDeclType.MEMORY, DataType.UBYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.MEMORY, DataType.UBYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, false, Position.DUMMY)
         val target = AssignTarget(IdentifierReference(listOf("address"), Position.DUMMY), null, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
         val subroutine = Subroutine("test", emptyList(), emptyList(), emptyList(), emptyList(), emptySet(), null, false, false, mutableListOf(decl, assignment), Position.DUMMY)
@@ -548,7 +548,7 @@ class TestMemory {
     @Test
     fun testNotInValidRamC64_memmap_variable() {
         val address = 0xd020
-        val decl = VarDecl(VarDeclType.MEMORY, DataType.UBYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.MEMORY, DataType.UBYTE, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, false, Position.DUMMY)
         val target = AssignTarget(IdentifierReference(listOf("address"), Position.DUMMY), null, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
         val subroutine = Subroutine("test", emptyList(), emptyList(), emptyList(), emptyList(), emptySet(), null, false, false, mutableListOf(decl, assignment), Position.DUMMY)
@@ -560,7 +560,7 @@ class TestMemory {
 
     @Test
     fun testInValidRamC64_array() {
-        val decl = VarDecl(VarDeclType.VAR, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", null, false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.VAR, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", null, false, false, false, Position.DUMMY)
         val arrayindexed = ArrayIndexedExpression(IdentifierReference(listOf("address"), Position.DUMMY), ArrayIndex(NumericLiteralValue.optimalInteger(1, Position.DUMMY), Position.DUMMY), Position.DUMMY)
         val target = AssignTarget(null, arrayindexed, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
@@ -574,7 +574,7 @@ class TestMemory {
     @Test
     fun testInValidRamC64_array_memmapped() {
         val address = 0x1000
-        val decl = VarDecl(VarDeclType.MEMORY, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.MEMORY, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, false, Position.DUMMY)
         val arrayindexed = ArrayIndexedExpression(IdentifierReference(listOf("address"), Position.DUMMY), ArrayIndex(NumericLiteralValue.optimalInteger(1, Position.DUMMY), Position.DUMMY), Position.DUMMY)
         val target = AssignTarget(null, arrayindexed, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)
@@ -588,7 +588,7 @@ class TestMemory {
     @Test
     fun testNotValidRamC64_array_memmapped() {
         val address = 0xe000
-        val decl = VarDecl(VarDeclType.MEMORY, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, Position.DUMMY)
+        val decl = VarDecl(VarDeclType.MEMORY, DataType.ARRAY_UB, ZeropageWish.DONTCARE, null, "address", NumericLiteralValue.optimalInteger(address, Position.DUMMY), false, false, false, Position.DUMMY)
         val arrayindexed = ArrayIndexedExpression(IdentifierReference(listOf("address"), Position.DUMMY), ArrayIndex(NumericLiteralValue.optimalInteger(1, Position.DUMMY), Position.DUMMY), Position.DUMMY)
         val target = AssignTarget(null, arrayindexed, null, Position.DUMMY)
         val assignment = Assignment(target, NumericLiteralValue.optimalInteger(0, Position.DUMMY), Position.DUMMY)

compilerAst/src/prog8/ast/AstToplevel.kt

@@ -297,7 +297,7 @@ class Program(val name: String,
             val varName = "string_${internedStringsBlock.statements.size}"
             val decl = VarDecl(
                 VarDeclType.VAR, DataType.STR, ZeropageWish.NOT_IN_ZEROPAGE, null, varName, string,
-                isArray = false, autogeneratedDontRemove = true, position = string.position
+                isArray = false, autogeneratedDontRemove = true, sharedWithAsm = false, position = string.position
             )
             internedStringsBlock.statements.add(decl)
             decl.linkParents(internedStringsBlock)

compilerAst/src/prog8/ast/antlr/Antr2Kotlin.kt

@@ -69,6 +69,7 @@ private fun prog8Parser.VariabledeclarationContext.toAst(encoding: IStringEncodi
                 it.expression().toAst(encoding),
                 vd.ARRAYSIG() != null || vd.arrayindex() != null,
                 false,
+                vd.SHARED()!=null,
                 it.toPosition()
         )
     }
@@ -85,6 +86,7 @@ private fun prog8Parser.VariabledeclarationContext.toAst(encoding: IStringEncodi
                 cvarinit.expression().toAst(encoding),
                 vd.ARRAYSIG() != null || vd.arrayindex() != null,
                 false,
+                vd.SHARED() != null,
                 cvarinit.toPosition()
         )
     }
@@ -101,6 +103,7 @@ private fun prog8Parser.VariabledeclarationContext.toAst(encoding: IStringEncodi
                 mvarinit.expression().toAst(encoding),
                 vd.ARRAYSIG() != null || vd.arrayindex() != null,
                 false,
+                vd.SHARED()!=null,
                 mvarinit.toPosition()
         )
     }
@@ -603,6 +606,7 @@ private fun prog8Parser.VardeclContext.toAst(encoding: IStringEncoding): VarDecl
             null,
             ARRAYSIG() != null || arrayindex() != null,
             false,
+            SHARED()!=null,
             toPosition()
     )
 }

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

@@ -164,6 +164,7 @@ open class VarDecl(val type: VarDeclType,
                    var value: Expression?,
                    val isArray: Boolean,
                    val autogeneratedDontRemove: Boolean,
+                   val sharedWithAsm: Boolean,
                    override val position: Position) : Statement(), ISymbolStatement {
     override lateinit var parent: Node
     var allowInitializeWithZero = true
@@ -183,7 +184,7 @@ open class VarDecl(val type: VarDeclType,
             val declaredType = ArrayToElementTypes.getValue(arrayDt)
             val arraysize = ArrayIndex.forArray(array)
             return VarDecl(VarDeclType.VAR, declaredType, ZeropageWish.NOT_IN_ZEROPAGE, arraysize, autoVarName, array,
-                    isArray = true, autogeneratedDontRemove = true, position = array.position)
+                    isArray = true, autogeneratedDontRemove = true, sharedWithAsm = false, position = array.position)
         }
 
         fun defaultZero(dt: DataType, position: Position) = when(dt) {
@@ -239,7 +240,7 @@ open class VarDecl(val type: VarDeclType,
     }
 
     fun copy(): VarDecl {
-        val c = VarDecl(type, declaredDatatype, zeropage, arraysize, name, value, isArray, autogeneratedDontRemove, position)
+        val c = VarDecl(type, declaredDatatype, zeropage, arraysize, name, value, isArray, autogeneratedDontRemove, sharedWithAsm, position)
         c.allowInitializeWithZero = this.allowInitializeWithZero
         return c
     }
@@ -247,7 +248,7 @@ open class VarDecl(val type: VarDeclType,
 
 // a vardecl used only for subroutine parameters
 class ParameterVarDecl(name: String, declaredDatatype: DataType, position: Position)
-    : VarDecl(VarDeclType.VAR, declaredDatatype, ZeropageWish.DONTCARE, null, name, null, false, true, position)
+    : VarDecl(VarDeclType.VAR, declaredDatatype, ZeropageWish.DONTCARE, null, name, null, false, true, false, position)
 
 class ArrayIndex(var indexExpr: Expression,
                  override val position: Position) : Node {

docs/source/programming.rst

@@ -202,6 +202,16 @@ Example::
     byte  @zp  zeropageCounter = 42
 
 
+*shared tag:*
+If you add the ``@shared`` tag to the variable declaration, the compiler will know that this variable
+is a prog8 variable shared with some assembly code elsewhere. This means that the assembly code can
+refer to the variable even if it's otherwise not used in prog8 code itself.
+(usually, these kinds of 'unused' variables are optimized away by the compiler, resulting in an error
+when assembling the rest of the code). Example::
+
+    byte  @shared  assemblyVariable = 42
+
+
 Integers
 ^^^^^^^^
 

docs/source/syntaxreference.rst

@@ -235,9 +235,11 @@ for them. You can give them an initial value as well. That value can be a simple
 or an expression. If you don't provide an intial value yourself, zero will be used.
 You can add a ``@zp`` zeropage-tag, to tell the compiler to prioritize it
 when selecting variables to be put into zeropage.
+You can add a ``@shared`` shared-tag, to tell the compiler that the variable is shared
+with some assembly code and that it should not be optimized away if not used elsewhere.
 The syntax is::
 
-	<datatype>  [ @zp ]  <variable name>   [ = <initial value> ]
+	<datatype>  [ @shared ] [ @zp ]  <variable name>   [ = <initial value> ]
 
 Various examples::
 
@@ -252,7 +254,8 @@ Various examples::
     byte[5]     values                  ; array of 5 bytes, initially set to zero
     byte[5]     values  = 255           ; initialize with five 255 bytes
 
-    word  @zp   zpword = 9999           ; prioritize this when selecting vars for zeropage storage
+    word  @zp     zpword = 9999         ; prioritize this when selecting vars for zeropage storage
+    word  @shared asmvar                ; variable is used in assembly code but not elsewhere
 
 
 Data types

docs/source/todo.rst

@@ -2,8 +2,7 @@
 TODO
 ====
 
-- possible idea: option to mark vardecls 'shared' to indicate they should not be optimized away because they're shared with assembly code?
+- should give error when passing invalid command line arguments
-  However: who even needs variables declared in prog8 code that are only used by assembly???
 
 - test all examples (including imgviewer, assembler and petaxian) before release of the new version
 

examples/test.p8

@@ -4,12 +4,31 @@ main {
 
     sub start() {
 
+        ubyte @shared xx=99
+        uword @shared asmvar
+        %asm {{
+            inc  xx
+            lda  asmvar
+            ldy  asmvar+1
+        }}
+        txt.nl()
+
         str string1 = "stringvalue\n"
         str string2 = "stringvalue\n"
         str string3 = "stringvalue\n"
         str string4 = "a"
         str string5 = "bb"
 
+        txt.print(string1)
+        txt.print(string2)
+        txt.print(string3)
+        string1[1]='?'
+        string2[2] = '?'
+        string3[3] = '?'
+        txt.print(string1)
+        txt.print(string2)
+        txt.print(string3)
+
         txt.print("a")
         txt.print("a")
         txt.print(string4)
@@ -18,9 +37,6 @@ main {
         txt.print(string5)
         txt.print("\n")
         txt.print("\n\n")
-        txt.print(string1)
-        txt.print(string2)
-        txt.print(string3)
         txt.print("hello\n")
         txt.print("hello\n")
         txt.print("hello\n")

parser/antlr/prog8.g4

@@ -62,11 +62,14 @@ ZEROPAGE :
     '@zp'
     ;
 
+SHARED :
+    '@shared'
+    ;
+
 ARRAYSIG :
     '[]'
     ;
 
-
 cpuregister: 'A' | 'X' | 'Y';
 register: 'A' | 'X' | 'Y' | 'AX' | 'AY' | 'XY' | 'Pc' | 'Pz' | 'Pn' | 'Pv' | 'R0' | 'R1' | 'R2' | 'R3' | 'R4' | 'R5' | 'R6' | 'R7' | 'R8' | 'R9' | 'R10' | 'R11' | 'R12' | 'R13' | 'R14' | 'R15';
 
@@ -134,7 +137,7 @@ directive :
 
 directivearg : stringliteral | identifier | integerliteral ;
 
-vardecl: datatype ZEROPAGE? (arrayindex | ARRAYSIG) ? varname=identifier ;
+vardecl: datatype SHARED? ZEROPAGE? (arrayindex | ARRAYSIG) ? varname=identifier ;
 
 varinitializer : vardecl '=' expression ;