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Compiler Speed Trials
#22
britlion Wrote:Oh yes - this:
Code:
LD HL, $2758      ; ??
   EXX          
   RET

I'm pretty sure this is setting HL' to the required value for BASIC before exiting. The Basic interpreter (and in particular the Interrupt service routine) assume that IY is pointed at the system variables and HL' is set to a specific value. I assume this one. Otherwise the spectrum can crash hard when dropping to BASIC from machine code.
Yes, I guess it's just that. If you look to ZX BASIC generated code, it stores IX (not needed), IY and HL', and recovers them on exit (unless returning with an error, RST #8). It's a pity IY is used for TIME interrupt, because IY could be very handy for managing data structures like Objects and structs. I think It would be a good idea to use IM2 for people wanting time-frames counting, without using IY.
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