fixed zp vars 0 initialization

Author: irmen

codeGenCpu6502/src/prog8/codegen/cpu6502/ProgramAndVarsGen.kt

@@ -328,10 +328,9 @@ internal class ProgramAndVarsGen(
         if (initializers.isNotEmpty()) {
             asmgen.out("prog8_init_vars\t.block")
             initializers.forEach { assign ->
-                if((assign.value as? PtNumber)?.number != 0.0 || allocator.isZpVar(assign.target.identifier!!.name))
+                val constvalue = assign.value as? PtNumber
+                if(constvalue==null || constvalue.number!=0.0 || allocator.isZpVar(assign.target.identifier!!.name))
                     asmgen.translate(assign)
-                else
-                    throw AssemblyError("non-zp variable should not be initialized to zero; it will be zeroed as part of BSS clear")
                 // the other variables that should be set to zero are done so as part of the BSS section clear.
             }
             asmgen.out("  rts\n  .bend")

codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt

@@ -75,7 +75,7 @@ class IRCodeGen(
                         initsToRemove += block to initialization
                     }
                     is PtNumber -> {
-                        require(initValue.number!=0.0) { "variable should not be initialized with 0, it will already be zeroed as part of BSS clear, initializer=$initialization" }
+                        require(initValue.number!=0.0 || variable.zpwish!=ZeropageWish.NOT_IN_ZEROPAGE) {"non-zp variable should not be initialized with 0, it will already be zeroed as part of BSS clear, initializer=$initialization" }
                         variable.setOnetimeInitNumeric(initValue.number)
                         initsToRemove += block to initialization
                     }

compiler/src/prog8/compiler/Compiler.kt

@@ -468,7 +468,7 @@ private fun processAst(program: Program, errors: IErrorReporter, compilerOptions
     errors.report()
     program.constantFold(errors, compilerOptions)
     errors.report()
-    program.reorderStatements(errors)
+    program.reorderStatements(compilerOptions, errors)
     errors.report()
     program.desugaring(errors, compilerOptions)
     errors.report()

compiler/src/prog8/compiler/astprocessing/AstExtensions.kt

@@ -20,8 +20,8 @@ internal fun Program.checkValid(errors: IErrorReporter, compilerOptions: Compila
     checker.visit(this)
 }
 
-internal fun Program.reorderStatements(errors: IErrorReporter) {
-    val reorder = StatementReorderer(this, errors)
+internal fun Program.reorderStatements(options: CompilationOptions, errors: IErrorReporter) {
+    val reorder = StatementReorderer(this, options, errors)
     reorder.visit(this)
     if(errors.noErrors()) {
         reorder.applyModifications()

compiler/src/prog8/compiler/astprocessing/SimplifiedAstMaker.kt

@@ -165,8 +165,11 @@ class SimplifiedAstMaker(private val program: Program, private val errors: IErro
             }
         }
 
-        if(srcAssign.origin == AssignmentOrigin.VARINIT && srcAssign.parent is Block && srcAssign.value.constValue(program)?.number==0.0)
-            throw FatalAstException("should not have a redundant block-level variable=0 assignment; it will be zeroed as part of BSS clear")
+        if(srcAssign.origin == AssignmentOrigin.VARINIT && srcAssign.parent is Block && srcAssign.value.constValue(program)?.number==0.0) {
+            val zeropages = srcAssign.target.targetIdentifiers().mapNotNull { it.targetVarDecl()?.zeropage }
+            if(zeropages.any {it==ZeropageWish.NOT_IN_ZEROPAGE})
+                throw FatalAstException("should not have a redundant block-level variable=0 assignment for a non-ZP variable; it will be zeroed as part of BSS clear")
+        }
 
         val assign = PtAssignment(srcAssign.position, srcAssign.origin==AssignmentOrigin.VARINIT)
         val multi = srcAssign.target.multi

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

@@ -5,13 +5,11 @@ import prog8.ast.expressions.*
 import prog8.ast.statements.*
 import prog8.ast.walk.AstWalker
 import prog8.ast.walk.IAstModification
-import prog8.code.core.AssociativeOperators
-import prog8.code.core.BaseDataType
-import prog8.code.core.DataType
-import prog8.code.core.IErrorReporter
+import prog8.code.core.*
 
 internal class StatementReorderer(
     val program: Program,
+    val options: CompilationOptions,
     val errors: IErrorReporter
 ) : AstWalker() {
     // Reorders the statements in a way the compiler needs.
@@ -114,10 +112,17 @@ internal class StatementReorderer(
     }
 
     private fun canSkipInitializationWith0(decl: VarDecl): Boolean {
-        // if the variable is declared in a block, we can omit the init with 0 because
-        // the variable will be initialized to zero when the BSS section is cleared as a whole.
-        if(decl.parent is Block)
-            return true
+        if(decl.parent is Block) {
+            // if the variable is declared in a block and is NOT in ZEROPAGE, we can omit the init with 0 because
+            // the variable will be initialized to zero when the BSS section is cleared as a whole.
+            if (decl.zeropage == ZeropageWish.NOT_IN_ZEROPAGE)
+                return true
+
+            // block level zp var that is not in zeropage, doesn't have to be cleared (will be done as part of bss clear at startup)
+            // note: subroutine level var HAS to be cleared because it needs to be zero at every subroutine call!
+            if (decl.zeropage == ZeropageWish.DONTCARE && options.zeropage == ZeropageType.DONTUSE)
+                return true
+        }
 
         // if there is an assignment to the variable below it (regular assign, or For loop),
         // and there is nothing important in between, we can skip the initialization.

compiler/test/codegeneration/TestVariables.kt

@@ -10,7 +10,10 @@ import prog8.ast.statements.Assignment
 import prog8.ast.statements.AssignmentOrigin
 import prog8.ast.statements.ForLoop
 import prog8.ast.statements.VarDecl
+import prog8.code.ast.PtAssignment
+import prog8.code.ast.PtNumber
 import prog8.code.target.C64Target
+import prog8.code.target.Cx16Target
 import prog8tests.helpers.ErrorReporterForTests
 import prog8tests.helpers.compileText
 
@@ -106,6 +109,7 @@ class TestVariables: FunSpec({
 
     test("global var init with array lookup should sometimes be const") {
         val src="""
+%zeropage dontuse            
 main {
 
     bool[] barray =  [true, false, true, false]
@@ -220,4 +224,85 @@ main {
         (st[5] as Assignment).target.identifier?.nameInSource shouldBe listOf("v1")
         (st[6] as Assignment).target.identifier?.nameInSource shouldBe listOf("v0")
     }
+
+    test("nondirty zp variables should be explicitly initialized to 0") {
+        val src="""
+main {
+    ubyte @shared @requirezp zpvar
+    ubyte @shared @requirezp @dirty dirtyzpvar
+
+    sub start() {
+        ubyte @shared @requirezp zpvar2
+        ubyte @shared @requirezp @dirty dirtyzpvar2
+    }
+}"""
+
+        val result = compileText(Cx16Target(), false, src, outputDir, writeAssembly = true)!!.codegenAst
+
+        val main = result!!.allBlocks().first { it.name=="p8b_main" }
+        main.children.size shouldBe 4
+        val zeroassignlobal =  main.children.single { it is PtAssignment } as PtAssignment
+        (zeroassignlobal.value as PtNumber).number shouldBe 0.0
+        zeroassignlobal.target.identifier!!.name shouldBe "p8b_main.p8v_zpvar"
+
+        val st = result.entrypoint()!!.children
+        st.size shouldBe 4
+        val zeroassign =  st.single { it is PtAssignment } as PtAssignment
+        (zeroassign.value as PtNumber).number shouldBe 0.0
+        zeroassign.target.identifier!!.name shouldBe "p8b_main.p8s_start.p8v_zpvar2"
+    }
+
+    test("nondirty non zp variables in block scope should not be explicitly initialized to 0 (bss clear takes care of it)") {
+        val src="""
+%zeropage dontuse
+
+main {
+    ubyte @shared v1
+    ubyte @shared @dirty dv1
+    sub start() {
+        ubyte @shared v2
+        ubyte @shared @dirty dv2
+    }
+}"""
+
+        val result = compileText(Cx16Target(), false, src, outputDir, writeAssembly = true)!!.codegenAst
+
+        // block level should not be intialized to 0 (will be done by BSS clear)
+        val main = result!!.allBlocks().first { it.name=="p8b_main" }
+        main.children.size shouldBe 3
+        main.children.any { it is PtAssignment } shouldBe false
+
+        // subroutine should be initialized to 0 because that needs to be done on every call to the subroutine
+        val st = result.entrypoint()!!.children
+        st.size shouldBe 4
+        val zeroassign =  st.single { it is PtAssignment } as PtAssignment
+        (zeroassign.value as PtNumber).number shouldBe 0.0
+        zeroassign.target.identifier!!.name shouldBe "p8b_main.p8s_start.p8v_v2"
+    }
+
+    test("nondirty explicit non zp variables in block scope should not be explicitly initialized to 0 (bss clear takes care of it)") {
+        val src="""
+main {
+    ubyte @shared @nozp v1
+    ubyte @shared @dirty @nozp dv1
+    sub start() {
+        ubyte @shared @nozp v2
+        ubyte @shared @dirty @nozp dv2
+    }
+}"""
+
+        val result = compileText(Cx16Target(), false, src, outputDir, writeAssembly = true)!!.codegenAst
+
+        // block level should not be intialized to 0 (will be done by BSS clear)
+        val main = result!!.allBlocks().first { it.name=="p8b_main" }
+        main.children.size shouldBe 3
+        main.children.any { it is PtAssignment } shouldBe false
+
+        // subroutine should be initialized to 0 because that needs to be done on every call to the subroutine
+        val st = result.entrypoint()!!.children
+        st.size shouldBe 4
+        val zeroassign =  st.single { it is PtAssignment } as PtAssignment
+        (zeroassign.value as PtNumber).number shouldBe 0.0
+        zeroassign.target.identifier!!.name shouldBe "p8b_main.p8s_start.p8v_v2"
+    }
 })

docs/source/todo.rst

@@ -1,7 +1,9 @@
 TODO
 ====
 
-BUG: fix ZP variables no longer getting initialized to 0 (see test.p8)
+Since fixing the missing zp-var initialization, programs grew in size again (assem)
+Are there any redundant block-level variable initializations to 0 that we can remove in peephole optimization for example?
+
 
 STRUCTS: are being developed in their own separate branch for now, called "structs".
 Idea is to make it feature complete in the IR/Virtual target, then merge it to master?, and then start building the 6502 code generation for it.

examples/test.p8

@@ -4,13 +4,47 @@
 %zpallowed 224,255
 
 main {
-    uword @shared @requirezp var1 = 0
-    uword @shared @requirezp var2 = 0
-    uword @shared @requirezp var3 = 0
-    uword @shared @requirezp var4 = 0
-    uword @shared @requirezp var5 = 0
+    uword @shared @requirezp zpvar1
+    uword @shared @requirezp zpvar2
+    uword @shared @requirezp zpvar3
+    uword @shared @requirezp zpvar4
+    uword @shared @requirezp zpvar5
+    uword @shared @requirezp @dirty dzpvar1
+    uword @shared @requirezp @dirty dzpvar2
+    uword @shared @requirezp @dirty dzpvar3
+    uword @shared @requirezp @dirty dzpvar4
+    uword @shared @requirezp @dirty dzpvar5
+    uword @shared @nozp var1
+    uword @shared @nozp var2
+    uword @shared @nozp var3
+    uword @shared @nozp var4
+    uword @shared @nozp var5
+    uword @shared @nozp @dirty dvar1
+    uword @shared @nozp @dirty dvar2
+    uword @shared @nozp @dirty dvar3
+    uword @shared @nozp @dirty dvar4
+    uword @shared @nozp @dirty dvar5
 
     sub start() {
+        txt.print("address start of zpvars: ")
+        txt.print_uw(&zpvar1)
+        txt.nl()
+        txt.print("address start of normal vars: ")
+        txt.print_uw(&var1)
+        txt.nl()
+
+        txt.print("non-dirty zp should all be 0: ")
+        txt.print_uw(zpvar1)
+        txt.spc()
+        txt.print_uw(zpvar2)
+        txt.spc()
+        txt.print_uw(zpvar3)
+        txt.spc()
+        txt.print_uw(zpvar4)
+        txt.spc()
+        txt.print_uw(zpvar5)
+        txt.nl()
+        txt.print("non-dirty should all be 0:    ")
         txt.print_uw(var1)
         txt.spc()
         txt.print_uw(var2)
@@ -22,6 +56,29 @@ main {
         txt.print_uw(var5)
         txt.nl()
 
+        txt.print("dirty zp may be random: ")
+        txt.print_uw(dzpvar1)
+        txt.spc()
+        txt.print_uw(dzpvar2)
+        txt.spc()
+        txt.print_uw(dzpvar3)
+        txt.spc()
+        txt.print_uw(dzpvar4)
+        txt.spc()
+        txt.print_uw(dzpvar5)
+        txt.nl()
+        txt.print("dirty may be random: ")
+        txt.print_uw(dvar1)
+        txt.spc()
+        txt.print_uw(dvar2)
+        txt.spc()
+        txt.print_uw(dvar3)
+        txt.spc()
+        txt.print_uw(dvar4)
+        txt.spc()
+        txt.print_uw(dvar5)
+        txt.nl()
+
         repeat {}
     }
 }

simpleAst/src/prog8/code/SymbolTable.kt

@@ -200,7 +200,7 @@ class StStaticVariable(name: String,
         // Certain codegens might want to put them back into the variable directly.
         // For strings and arrays this doesn't occur - these are always already specced at creation time.
 
-        require(number!=0.0) { "variable should not be initialized with 0, it will already be zeroed as part of BSS clear" }
+        require(number!=0.0 || zpwish!=ZeropageWish.NOT_IN_ZEROPAGE) { "non-zp variable should not be initialized with 0, it will already be zeroed as part of BSS clear" }
         initializationNumericValue = number
     }