From 3b0d7ea960b60998b7e9d132248c4dc796da9f00 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Wed, 8 Nov 2023 22:04:41 +0100
Subject: [PATCH] better const-evaluation of addressOf a memory mapped variable

---
 .../optimizer/ConstantIdentifierReplacer.kt      | 16 ++++++++++++++--
 compiler/test/ast/TestVariousCompilerAst.kt      | 13 +++++++++++++
 .../src/prog8/ast/expressions/AstExpressions.kt  | 10 +++++++++-
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt b/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
index 6f1bc8f33..a1208b55d 100644
--- a/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
+++ b/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
@@ -251,7 +251,16 @@ internal class ConstantIdentifierReplacer(private val program: Program, private
             return noModifications
         }
 
-        if(decl.type== VarDeclType.CONST || decl.type== VarDeclType.VAR) {
+        if(decl.isArray && decl.type==VarDeclType.MEMORY) {
+            val memaddr = decl.value?.constValue(program)
+            if(memaddr!=null && memaddr !== decl.value) {
+                return listOf(IAstModification.SetExpression(
+                    { decl.value = it }, memaddr, decl
+                ))
+            }
+        }
+
+        if(decl.type==VarDeclType.CONST || decl.type==VarDeclType.VAR) {
             if(decl.isArray){
                 val arraysize = decl.arraysize
                 if(arraysize==null) {
@@ -291,8 +300,11 @@ internal class ConstantIdentifierReplacer(private val program: Program, private
     }
 
     private fun createConstArrayInitializerValue(decl: VarDecl): ArrayLiteral? {
-        // convert the initializer range expression from a range or int, to an actual array.
 
+        if(decl.type==VarDeclType.MEMORY)
+            return null     // memory mapped arrays can never have an initializer value other than the address where they're mapped.
+
+        // convert the initializer range expression from a range or int, to an actual array.
         when(decl.datatype) {
             DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W, DataType.ARRAY_W_SPLIT, DataType.ARRAY_UW_SPLIT -> {
                 val rangeExpr = decl.value as? RangeExpression
diff --git a/compiler/test/ast/TestVariousCompilerAst.kt b/compiler/test/ast/TestVariousCompilerAst.kt
index 16b66ff48..a6918bc28 100644
--- a/compiler/test/ast/TestVariousCompilerAst.kt
+++ b/compiler/test/ast/TestVariousCompilerAst.kt
@@ -366,5 +366,18 @@ main {
         compileText(VMTarget(), optimize=false, src, writeAssembly=false, errors = errors) shouldBe null
         errors.errors.single() shouldContain  "cannot use byte value"
     }
+
+    test("const eval of address-of a memory mapped variable") {
+        val src = """
+main {
+    sub start() {
+        &ubyte mappedvar = 1000
+        cx16.r0 = &mappedvar
+        &ubyte[8] array = &mappedvar
+        cx16.r0 = &array
+    }
+}"""
+        compileText(VMTarget(), optimize=false, src, writeAssembly=false) shouldNotBe null
+    }
 })
 
diff --git a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
index 8cdfeccdd..b3f79a3c8 100644
--- a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
+++ b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
@@ -395,7 +395,15 @@ data class AddressOf(var identifier: IdentifierReference, var arrayIndex: ArrayI
     }
 
     override fun copy() = AddressOf(identifier.copy(), arrayIndex?.copy(), position)
-    override fun constValue(program: Program): NumericLiteral? = null
+    override fun constValue(program: Program): NumericLiteral? {
+        val target = this.identifier.targetStatement(program) as? VarDecl
+        if(target?.type==VarDeclType.MEMORY) {
+            val address = target.value?.constValue(program)
+            if(address!=null)
+                return NumericLiteral(DataType.UWORD, address.number, position)
+        }
+        return null
+    }
     override fun referencesIdentifier(nameInSource: List<String>) = identifier.nameInSource==nameInSource || arrayIndex?.referencesIdentifier(nameInSource)==true
     override fun inferType(program: Program) = InferredTypes.knownFor(DataType.UWORD)
     override fun accept(visitor: IAstVisitor) = visitor.visit(this)