Am 30.07.21 um 15:12 schrieb a...@etchedpixels.co.uk:
> On Tue, 27 Jul 2021 23:15:32 +0200
> Philipp Klaus Krause <p...@spth.de> wrote:
>
>> A new calling convention for z80ยน has been implemented in the
>> breaktheworld branch:
>> https://sourceforge.net/p/sdcc/code/HEAD/tree/branches/breaktheworld/
>>
>> Anyone wanting to test it or experiment with it is welcome to use the
>> branch.
I don't think there will be big changes to what is implemented in the
branch, but I can't fully rule them out either - especially wrt. stack
cleanup for funtions returning float. Also, if many SDCC users dislike
the proposed changes, there is still the possibility of not changing the
convention at all.
> It would be useful if you described the change as it's a bit hard to
> assess a new ABI without explanation.
There is documentation in the manual in that branch, but here are the
changes (for z80, z180, z80n - other ports are likely to use something
else):
* Return values:
- Old: l for 8 bit, hl for 16 bit, dehl for 32 bit
- New: a for 8 bit, de for 16 bit, hlde for 32 bit
* Parameters:
- Old: Always all on stack
- New: All on stack for functions with variable arguments, otherwise:
- First parameter in a if 8 bit, hl if 16 bit, hlde if 32 bit.
- If first parameter is in a, and second has 8 bits, it is in l
- If first parameter is in a or hl, and the second has 16 bits,
it is in de
- Other parameters on the stack
* Stack cleanup:
- Always done by caller
- New: Done by caller with the following exceptions:
- Functions that return at most 16 bits (e.g. void, char, int) and
do not have variable arguments
- Functions that return float and
have a first parameter of type float and
do not have variable arguments
> Also can we please have defines
> from the compiler for ABI breakage so that code can do
>
> #if (__SDCC_Z80_ABI == 2)
> #define asmcall xxx
> #else
> #define asmcall yyy
> #endif
The original plan was to just use the version number. But since it now
has become clear that some users would not want the change, if we still
change the default, we'd need such a define to go along with a
--stdccoldcall command-line option to restore the old default behaviour.
Philipp
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