From b89ad4b3285d98f54396446d523c7aefb59b9a47 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 29 Jul 2023 18:25:52 +0200
Subject: [PATCH] don't optimize empty where choice away! It would call the
 else clause incorrectly.

---
 .../prog8/codegen/intermediate/IRCodeGen.kt   | 15 ++++++++---
 .../compiler/astprocessing/VariousCleanups.kt | 10 -------
 docs/source/todo.rst                          |  2 ++
 examples/test.p8                              | 27 ++++++-------------
 4 files changed, 21 insertions(+), 33 deletions(-)

diff --git a/codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt b/codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt
index 49ab1b0f9..bad29de77 100644
--- a/codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt
+++ b/codeGenIntermediate/src/prog8/codegen/intermediate/IRCodeGen.kt
@@ -413,10 +413,17 @@ class IRCodeGen(
                 result += translateNode(choice.statements)
                 addInstr(result, IRInstruction(Opcode.JUMP, labelSymbol = endLabel), null)
             } else {
-                val choiceLabel = createLabelName()
-                choices.add(choiceLabel to choice)
-                choice.values.children.map { it as PtNumber }.sortedBy { it.number }.forEach { value ->
-                    addInstr(result, IRInstruction(Opcode.BEQ, valueDt, reg1=valueTr.resultReg, immediate = value.number.toInt(), labelSymbol = choiceLabel), null)
+                if(choice.statements.children.isEmpty()) {
+                    // no statements for this choice value, jump to the end immediately
+                    choice.values.children.map { it as PtNumber }.sortedBy { it.number }.forEach { value ->
+                        addInstr(result, IRInstruction(Opcode.BEQ, valueDt, reg1=valueTr.resultReg, immediate = value.number.toInt(), labelSymbol = endLabel), null)
+                    }
+                } else {
+                    val choiceLabel = createLabelName()
+                    choices.add(choiceLabel to choice)
+                    choice.values.children.map { it as PtNumber }.sortedBy { it.number }.forEach { value ->
+                        addInstr(result, IRInstruction(Opcode.BEQ, valueDt, reg1=valueTr.resultReg, immediate = value.number.toInt(), labelSymbol = choiceLabel), null)
+                    }
                 }
             }
         }
diff --git a/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt b/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
index 0b377748b..7b3658af1 100644
--- a/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
+++ b/compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt
@@ -262,15 +262,5 @@ internal class VariousCleanups(val program: Program, val errors: IErrorReporter,
         }
         return noModifications
     }
-
-    override fun after(whenStmt: When, parent: Node): Iterable<IAstModification> {
-        val removals = mutableListOf<Int>()
-        whenStmt.choices.withIndex().forEach { (index, choice) ->
-            if(choice.statements.isEmpty())
-                removals.add(index)
-        }
-        removals.reversed().forEach { whenStmt.choices.removeAt(it) }
-        return noModifications
-    }
 }
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index e38dc43c6..fff5915f8 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -1,6 +1,8 @@
 TODO
 ====
 
+- compiling Rockrunner with -noopt crashes the program soon after startup
+
 - IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction
 - IR: reduce amount of CMP/CMPI after instructions that set the status bits correctly (LOADs? INC? etc), but only after setting the status bits is verified!
 
diff --git a/examples/test.p8 b/examples/test.p8
index 2e97cdea7..681d459c2 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,27 +1,16 @@
-%import gfx2
 %import textio
+%zeropage basicsafe
 
 main {
     sub start() {
-        gfx2.screen_mode(6)         ; 1 and 5 are lo-res and hi-res monochrome
+        ubyte var = 0
 
-        uword xx
-        gfx2.rect(10, 10, 180, 140, 3)
-        gfx2.rect(12, 12, 180, 140, 3)
-
-        cbm.SETTIM(0,0,0)
-
-        for xx in 5 to 100 {
-            gfx2.text(xx, xx, 1, sc:"hello world! should be pixel-aligned.")
-            gfx2.text(xx, xx, 2, sc:"hello world! should be pixel-aligned.")
-            gfx2.text(xx, xx, 3, sc:"hello world! should be pixel-aligned.")
-            gfx2.text(xx, xx, 0, sc:"hello world! should be pixel-aligned.")
+        when var {
+            1 -> txt.print("one")
+            2 -> txt.print("two")
+            0 -> {
+            }
+            else -> txt.print("other")
         }
-
-        gfx2.screen_mode(0)
-        txt.print_uw(cbm.RDTIM16())
-        txt.print(" jiffies")
-
-        repeat { }
 	}
 }