mirror of
https://github.com/KarolS/millfork.git
synced 2024-05-31 18:41:30 +00:00
87 lines
3.0 KiB
Markdown
87 lines
3.0 KiB
Markdown
[< back to index](../doc_index.md)
|
||
|
||
# Optimization hints
|
||
|
||
Optimization hints are optional annotations for functions and variables
|
||
that allow the compiler to make extra assumptions that help with code optimization.
|
||
|
||
The general idea is that removing or disabling optimization hints will not break the code,
|
||
but adding invalid optimization hints may break the code.
|
||
|
||
Every optimization hint's name starts with an exclamation mark.
|
||
|
||
Optimization hints marked with **(X)** currently do nothing and are planned to be implemented in the future.
|
||
|
||
## Hints for functions
|
||
|
||
* `!preserves_memory` – the function does not write to memory
|
||
|
||
* `!idempotent` – calling the function multiple times in succession has no effect
|
||
|
||
* `!hot` – the function is hot and should be optimized for speed at the cost of increased size
|
||
|
||
* `!cold` **(X)** – the function is cold and should be optimized for size at the cost of increased run time
|
||
|
||
* `!odd` – the function returns an odd value
|
||
|
||
* `!even` – the function returns an even value
|
||
|
||
## Hints for 6502 assembly functions
|
||
|
||
These hints have only effect when used on an assembly function on a 6502 target:
|
||
|
||
* `!preserves_a` – the function preserves the contents of the A register
|
||
|
||
* `!preserves_x` – the function preserves the contents of the X register
|
||
|
||
* `!preserves_y` – the function preserves the contents of the Y register
|
||
|
||
* `!preserves_c` – the function preserves the contents of the carry flag
|
||
|
||
## Hints for 8080/Z80/LR35902 assembly functions
|
||
|
||
These hints have only effect when used on an assembly function on a 8080-like target:
|
||
|
||
* `!preserves_a` – the function preserves the contents of the A register
|
||
|
||
* `!preserves_bc` – the function preserves the contents of the B and C registers
|
||
|
||
* `!preserves_de` – the function preserves the contents of the D and E registers
|
||
|
||
* `!preserves_hl` – the function preserves the contents of the H and L registers
|
||
|
||
* `!preserves_hl` – the function preserves the contents of the H and L registers
|
||
|
||
* `!preserves_cf` – the function preserves the contents of the carry flag
|
||
|
||
## Hints for 6809 assembly functions
|
||
|
||
These hints have only effect when used on an assembly function on a 6809 target:
|
||
|
||
* `!preserves_a` – the function preserves the contents of the A register
|
||
|
||
* `!preserves_b` – the function preserves the contents of the B register
|
||
|
||
* `!preserves_d` – the function preserves the contents of the A and B register
|
||
|
||
* `!preserves_dp` **(X)** – the function preserves the contents of the DP register; exceptionally this can also be used on non-assembly functions
|
||
|
||
* `!preserves_x` – the function preserves the contents of the X register
|
||
|
||
* `!preserves_y` – the function preserves the contents of the Y register
|
||
|
||
* `!preserves_u` – the function preserves the contents of the U register
|
||
|
||
* `!preserves_c` – the function preserves the contents of the carry flag
|
||
|
||
## Hints for variables
|
||
|
||
* `!odd` **(X)** – the variable can only contain odd values
|
||
|
||
* `!even` **(X)** – the variable can only contain even values
|
||
|
||
|
||
|
||
|
||
|