mirror of
https://github.com/KarolS/millfork.git
synced 2025-02-09 21:30:55 +00:00
55 lines
1.4 KiB
Markdown
55 lines
1.4 KiB
Markdown
|
[< back to index](../index.md)
|
||
|
|
|
||
|
|
# Millfork calling convention
|
||
|
|
|
||
|
|
**Note:** all the info below may change without any warning and is given only for debugging purposes.
|
||
|
|
|
||
|
|
## 6502
|
||
|
|
|
||
|
|
#### Parameters:
|
||
|
|
|
||
|
|
* if the function has one parameter of size one byte, it is passed via the A register
|
||
|
|
|
||
|
|
* otherwise, all parameters are passed via static locations
|
||
|
|
|
||
|
|
#### Return values:
|
||
|
|
|
||
|
|
* one-byte return values are passed via the A register
|
||
|
|
|
||
|
|
* two-byte return values are passed via the A (low byte) and X (high byte) register
|
||
|
|
|
||
|
|
#### Register preservation:
|
||
|
|
|
||
|
|
* callee may clobber all three registers (A, X, Y) and most flags (Z, V, C, N, and also I if using inline assembly)
|
||
|
|
|
||
|
|
* callee expects the D flag to be clear and will leave it clear
|
||
|
|
|
||
|
|
* on 65816: callee will preserve the emulation flag
|
||
|
|
(setting the emulation flag correctly is the responsibility of the initialization code)
|
||
|
|
|
||
|
|
* on 65816 in native mode:
|
||
|
|
|
||
|
|
* callee expects the M and X flag to be set and will leave them set
|
||
|
|
(8-bit accumulator and index registers by default)
|
||
|
|
|
||
|
|
* callee expects the direct page register to be set to 0000 and will not change it
|
||
|
|
|
||
|
|
## Z80
|
||
|
|
|
||
|
|
#### Parameters:
|
||
|
|
|
||
|
|
* all parameters are passed via static locations
|
||
|
|
|
||
|
|
#### Return values:
|
||
|
|
|
||
|
|
* one-byte return values are passed via the A register
|
||
|
|
|
||
|
|
* two-byte return values are passed via the HL register pair
|
||
|
|
|
||
|
|
#### Register preservation:
|
||
|
|
|
||
|
|
* callee may clobber all flags
|
||
|
|
|
||
|
|
* callee may clobber all registers except for IX, IY and shadow registers
|
||
|
|
|