added 'align_word' and 'align_page' block options to control block start address alignment in the assembler

compiler/src/prog8/compiler/astprocessing/AstChecker.kt

@@ -752,7 +752,7 @@ internal class AstChecker(private val program: Program,
                     err("this directive may only occur in a block or at module level")
                 if(directive.args.isEmpty())
                     err("missing option directive argument(s)")
-                else if(directive.args.map{it.name in setOf("enable_floats", "force_output", "no_sysinit")}.any { !it })
+                else if(directive.args.map{it.name in setOf("enable_floats", "force_output", "no_sysinit", "align_word", "align_page")}.any { !it })
                     err("invalid option directive argument(s)")
             }
             "%target" -> {

compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt

@@ -181,8 +181,13 @@ internal class AsmGen(private val program: Program,
         out("\n\n; ---- block: '${block.name}' ----")
         if(block.address!=null)
             out("* = ${block.address!!.toHex()}")
-        else
-            out("\t.align 2")
+        else {
+            if("align_word" in block.options())
+                out("\t.align 2")
+            else if("align_page" in block.options())
+                out("\t.align $100")
+        }
+
         out("${block.name}\t" + (if("force_output" in block.options()) ".block\n" else ".proc\n"))
 
         outputSourceLine(block)

docs/source/syntaxreference.rst

@@ -120,17 +120,18 @@ Directives
 	Level: module, block.
 	Sets special compiler options.
 
-    - For a module option, there is ``enable_floats``, which will tell the compiler
+    - ``enable_floats`` (module level) tells the compiler
       to deal with floating point numbers (by using various subroutines from the Commodore-64 kernal).
       Otherwise, floating point support is not enabled. Normally you don't have to use this yourself as
       importing the ``floats`` library is required anyway and that will enable it for you automatically.
-    - There's also ``no_sysinit`` which cause the resulting program to *not* include
+    - ``no_sysinit`` (module level) which cause the resulting program to *not* include
       the system re-initialization logic of clearing the screen, resetting I/O config etc. You'll have to
       take care of that yourself. The program will just start running from whatever state the machine is in when the
       program was launched.
-    - When used in a block with the ``force_output`` option, it will force the block to be outputted
-      in the final program. Can be useful to make sure some
-      data is generated that would otherwise be discarded because it's not referenced (such as sprite data).
+    - ``force_output`` (in a block) will force the block to be outputted in the final program.
+      Can be useful to make sure some data is generated that would otherwise be discarded because it's not referenced (such as sprite data).
+    - ``align_word`` (in a block) will make the assembler align the start address of this block on a word boundary in memory (so, an even memory address).
+    - ``align_page`` (in a block) will make the assembler align the start address of this block on a page boundary in memory (so, the LSB of the address is 0).
 
 
 .. data:: %asmbinary "<filename>" [, <offset>[, <length>]]

docs/source/todo.rst

@@ -16,7 +16,7 @@ TODO
 - refactor the compiler optimizers into their own submodule?
 - optimizer: detect variables that are written but never read - mark those as unused too and remove them, such as uword unused = memory("unused222", 20) - also remove the memory slab allocation
 - add a compiler option to not remove unused subroutines. this allows for building library programs
-- make it possible to use cpu opcodes such as 'nop' as variable names by prefixing all asm vars with something such as 'v_'
+- make it possible to use cpu opcodes such as 'nop' as variable names by prefixing all asm vars with something such as ``v_``
 - option to load the built-in library files from a directory instead of the embedded ones (for easier library development/debugging)
 - c64: make the graphics.BITMAP_ADDRESS configurable (VIC banking)
 - some support for recursive subroutines?

examples/test.p8

@@ -4,9 +4,13 @@
 
 main {
 
+;   $1F9C0 - $1F9FF 	PSG registers
+
     sub start() {
         uword xx = &b2.zz
         xx=&b3.zz
+        xx=&b4.zz
+        xx=&b5.zz
 
         txt.print_uwhex(&main, true)
         txt.nl()
@@ -14,6 +18,10 @@ main {
         txt.nl()
         txt.print_uwhex(&b3, true)
         txt.nl()
+        txt.print_uwhex(&b4, true)
+        txt.nl()
+        txt.print_uwhex(&b5, true)
+        txt.nl()
     }
 }
 
@@ -24,3 +32,15 @@ b2 {
 b3 $4001 {
     str zz="bye"
 }
+
+b4 {
+    %option align_word
+
+    str zz="wut"
+}
+
+b5 {
+    %option align_page
+
+    str zz="wut2"
+}