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Re: Design a microcontroller for gcc
> BTW, carry-out from shifts is very rarely used in compiled code.)
Unless you've expanded SI shifts into a pair of HI shifts.
> Besides what DJ said about performance (both pros and cons
> there), the problem is as I said with port complexity, because
> of the way you have to handle condition codes in gcc.
Unless you tell gcc that the condition codes are hard register?
That's what m32c does; it has separate cmp/jmp and most opcodes set
flags, so I just set an attribute that says which flags are set by
each insn. Then, I can add a reorg pass to delete the cmps if the
previous insn that set the flags happened to set them right.
> Anyway, at least keep a way to add reg+reg and reg+integer, load and
> store of memory and load of integer and address without condition
> code effects and your port has a chance to avoid the related bloat.
At least, move/load/store shouldn't touch flags.