Quoting Jeremy Bennett <[email protected]>:
I've always liked having R0 hard-wired to zero. Having a destination register that ignored what was written to it was useful. However compiler technology has moved on, and I suspect that it now makes no difference. I've copied amylaar, as local GCC guru, to see if he has any comment.
I don't think it would make much of a difference for openrisc, as it has special compare instructions in the first place. The absence of register clobbers (except for LINK_REGNUM) in the machine description speaks for itself. For architectures like Epiphany, where arithmetic operations that write to a register are used to perform comparisons, it would be more of a convenience. But as you can see from the Epiphany machine description, it can still do without, by requiring a temporary register to clobber. _______________________________________________ OpenRISC mailing list [email protected] http://lists.openrisc.net/listinfo/openrisc
