fix a problem with const fold optimization in if expressions, and IR compilation of that

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

@@ -1451,6 +1451,10 @@ class IRCodeGen(
         }
 
         when(val cond=ifElse.condition) {
+            is PtBool -> {
+                // normally this will be optimized away, but not with -noopt
+                translateSimple(cond, Opcode.BSTEQ)
+            }
             is PtTypeCast -> {
                 require(cond.type==DataType.BOOL && cond.value.type in NumericDatatypes)
                 translateSimple(cond, Opcode.BSTEQ)

compiler/src/prog8/compiler/Compiler.kt

@@ -458,8 +458,13 @@ private fun optimizeAst(program: Program, compilerOptions: CompilationOptions, e
             break
     }
     removeUnusedCode(program, errors, compilerOptions)
-    if(errors.noErrors())
+    if(errors.noErrors()) {
+        // last round of optimizations because constFold may have enabled more...
+        program.simplifyExpressions(errors, compilerOptions)
+        program.optimizeStatements(errors, functions, compilerOptions)
         program.constantFold(errors, compilerOptions) // because simplified statements and expressions can result in more constants that can be folded away
+    }
+
     errors.report()
 }
 

examples/test.p8

@@ -1,28 +1,16 @@
-%import bmx
-%import diskio
-%import emudbg
-%import floats
-%import gfx2
-%import graphics
-%import monogfx
-%import palette
-%import psg
-%import sprites
-%import syslib
 %import textio
-%import verafx
-%import conv
-%import cx16logo
-%import math
-%import prog8_lib
-%import string
-%import test_stack
-
 %zeropage basicsafe
 %option no_sysinit
 
 main {
     sub start() {
+        const ubyte x=0
+
+        if x==3 {
+            txt.print("three")
+        } else if x==4 {
+            txt.print("four")
+        }
     }
 }