From 67b0890a6e5a4f70881d564c82108f0d2eaaa21b Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 25 Dec 2021 23:30:09 +0100
Subject: [PATCH] remove unneeded var inits when an assignment is already
 present

---
 compiler/src/prog8/compiler/Compiler.kt                   | 4 ++--
 .../prog8/compiler/astprocessing/StatementReorderer.kt    | 8 ++++++++
 compiler/test/TestOptimization.kt                         | 7 ++++---
 compiler/test/TestSubroutines.kt                          | 6 +++---
 examples/test.p8                                          | 8 ++++++++
 5 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/compiler/src/prog8/compiler/Compiler.kt b/compiler/src/prog8/compiler/Compiler.kt
index 9f90b282b..3df6c6324 100644
--- a/compiler/src/prog8/compiler/Compiler.kt
+++ b/compiler/src/prog8/compiler/Compiler.kt
@@ -76,8 +76,8 @@ fun compileProgram(args: CompilerArguments): CompilationResult {
                 )
             postprocessAst(program, args.errors, compilationOptions)
 
-            println("*********** AST BEFORE ASSEMBLYGEN *************")
-            printProgram(program)
+//            println("*********** AST BEFORE ASSEMBLYGEN *************")
+//            printProgram(program)
 
             if (args.writeAssembly) {
                 when (val result = writeAssembly(program, args.errors, args.outputDir, args.quietAssembler, compilationOptions)) {
diff --git a/compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt b/compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt
index 03d11b61f..df017928c 100644
--- a/compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt
+++ b/compiler/src/prog8/compiler/astprocessing/StatementReorderer.kt
@@ -59,6 +59,14 @@ internal class StatementReorderer(val program: Program,
                             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
                         val hasNextForWithThisLoopvar = nextFor?.loopVar?.nameInSource==listOf(decl.name)
                         if (!hasNextForWithThisLoopvar) {
diff --git a/compiler/test/TestOptimization.kt b/compiler/test/TestOptimization.kt
index e070f24da..0eb0f01aa 100644
--- a/compiler/test/TestOptimization.kt
+++ b/compiler/test/TestOptimization.kt
@@ -633,14 +633,13 @@ class TestOptimization: FunSpec({
         uword zz
         zz = 60
         ubyte xx
-        xx = 0
         xx = sin8u(xx)
         xx += 6
          */
         val stmts = result.program.entrypoint.statements
-        stmts.size shouldBe 8
+        stmts.size shouldBe 7
         stmts.filterIsInstance<VarDecl>().size shouldBe 3
-        stmts.filterIsInstance<Assignment>().size shouldBe 5
+        stmts.filterIsInstance<Assignment>().size shouldBe 4
     }
 
     test("only substitue assignments with 0 after a =0 initializer if it is the same variable") {
@@ -666,6 +665,8 @@ class TestOptimization: FunSpec({
         yy = 0
         xx += 10
          */
+        printProgram(result.program)
+
         val stmts = result.program.entrypoint.statements
         stmts.size shouldBe 7
         stmts.filterIsInstance<VarDecl>().size shouldBe 2
diff --git a/compiler/test/TestSubroutines.kt b/compiler/test/TestSubroutines.kt
index ac56cdae0..88a43e025 100644
--- a/compiler/test/TestSubroutines.kt
+++ b/compiler/test/TestSubroutines.kt
@@ -206,14 +206,14 @@ class TestSubroutines: FunSpec({
         val block = module.statements.single() as Block
         val thing = block.statements.filterIsInstance<Subroutine>().single {it.name=="thing"}
         block.name shouldBe "main"
-        thing.statements.size shouldBe 11          // rr paramdecl, xx, xx assign, yy decl, yy init 0, yy assign, other, other assign 0, zz, zz assign, return
+        thing.statements.size shouldBe 10          // rr paramdecl, xx, xx assign, yy decl, yy assign, other, other assign 0, zz, zz assign, return
         val xx = thing.statements[1] as VarDecl
         withClue("vardecl init values must have been moved to separate assignments") {
             xx.value shouldBe null
         }
         val assignXX = thing.statements[2] as Assignment
-        val assignYY = thing.statements[5] as Assignment
-        val assignZZ = thing.statements[9] as Assignment
+        val assignYY = thing.statements[4] as Assignment
+        val assignZZ = thing.statements[8] as Assignment
         assignXX.target.identifier!!.nameInSource shouldBe listOf("xx")
         assignYY.target.identifier!!.nameInSource shouldBe listOf("yy")
         assignZZ.target.identifier!!.nameInSource shouldBe listOf("zz")
diff --git a/examples/test.p8 b/examples/test.p8
index b1f07e8e4..d06525874 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -2,6 +2,14 @@
 %zeropage basicsafe
 
 main {
+    ubyte @shared foo=99
+      sub thing(uword rr) {
+        ubyte @shared xx = rr[1]    ; should still work as var initializer that will be rewritten
+        ubyte @shared yy
+        yy = rr[2]
+        uword @shared other
+        ubyte @shared zz = other[3]
+      }
     sub start() {
         ubyte @shared xx
         repeat {