Library doesn't preserve IY register in SMSlib_PSGaiden.c

[aralbrec]

Unless programs are compiled with the --reserve-regs-iy flag, SDCC expects the IY register to be preserved across calls just like IX.

In SMSlib_PSGaiden.c, IY is used but is not saved. IX is saved.

[sverx]

According to the SDCC manual, if I got the meaning correctly, it should be the other way around.
As we're not using the --reserve-regs-iy flag, IY can be used as a temporary register, as written in section 4.3 of the manual:

Register A, B, C, D, E, H, L and IY are used as a temporary registers for holding variables.

[aralbrec]

I mistyped there - in the above I meant the --reserve-regs-iy flag which I have corrected in the original post.

Despite what the manual says, I have come across instances where sdcc has used an old IY value across a function call that did not indicate IY was preserved. I tried some test compiles tonight to try to find an example without success but I will continue to try a few more and see if I can find an example.

[sverx]

If you find that some generated code is assuming that IY is unchanged after a call, then it might be an SDCC error - or you might have called a function that has a __preserves_regs( ) declaration attached to it.
In either case please let me know. I'm leaving this open for your feedback :)

(I also edited my last post to fix that --reserve-regs-iy)

[sverx]

closing this