Apple-2-SW/prog8
1
0
Fork 0
mirror of https://github.com/irmen/prog8.git synced 2024-11-26 11:49:22 +00:00
Code Issues Projects Releases Wiki Activity

doc

Browse Source
This commit is contained in:
Irmen de Jong 2024-06-29 13:39:08 +02:00
parent 8efa89165c
commit bbf621a8c4
3 changed files with 6 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
docs/source/programming.rst
View File

@ -342,16 +342,14 @@ See also :ref:`pointervars_programming`
**LSB/MSB split word arrays:**
For (u)word arrays, you can make the compiler layout the array in memory as two separate arrays,
one with the LSBs and one with the MSBs of the word values. This is more efficient when storing
and reading words from the array (the index can be used twice).
Add the ``@split`` tag to the variable declaration to do this.
In the assembly code, the array will be generated as two byte arrays namely ``name_lsb`` and ``name_msb``.
Note that the maximum length of a split word array is 256! (regular word arrays are limited to 128 elements).
one with the LSBs and one with the MSBs of the word values. This makes it more efficient to access
values from the array (smaller and faster code). It also doubles the maximum size of the array from 128 words to 256 words!
The ``@split`` tag should be added to the variable declaration to do this.
In the assembly code, the array will then be generated as two byte arrays namely ``name_lsb`` and ``name_msb``.
.. caution::
Not all array operations are supported yet on "split word arrays".
The compiler may give an unpleasant error or crash when you hit such a case in your code.
If this happens simply revert to a regular word array and please report the issue,
If you get an error message, simply revert to a regular word array and please report the issue,
so that more support can be added in the future where it is needed.

2
docs/source/syntaxreference.rst
View File

@ -344,7 +344,7 @@ Tag Effect
@requirezp force the variable into Zero page. If ZP is full, compilation will fail.
@nozp force the variable to normal system ram, never place it into zeropage.
@shared means the variable is shared with some assembly code and that it cannot be optimized away if not used elsewhere.
@split (only valid on (u)word arrays) Makes the array to be placed in memory as 2 separate byte arrays; one with the LSBs one with the MSBs of the word values. May improve performance.
@split (only valid on (u)word arrays) Makes the array to be placed in memory as 2 separate byte arrays; one with the LSBs one with the MSBs of the word values. Usually improves performance and code size.
========== ======

2
docs/source/todo.rst
View File

@ -1,8 +1,6 @@
TODO
====
docs: stress more that the @split for word arrays can provide significant code efficiency over normal linear word array
optimizer bug, see "optimizing inlined functions must reference proper scopes" unittest (skipped for now)
causes compiler error for virtual: just calling txt.cls() gives compile error undefined symbol clear_screen