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Re: [PATCH] RTL docs update

Richard Sandiford wrote:
> ""Seongbae Park (박성배, 朴成培)"" <> writes:
>> +   FIXME: Replace all uses of UNSPEC that appears by itself or as a component
>> +   of a PARALLEL with USE.
> I'm still not convinced by this.  How should SPU's:
> (define_insn "iprefetch"
>   [(unspec [(const_int 0)] UNSPEC_IPREFETCH)]
>   ""
>   "hbrp"
>   [(set_attr "type" "iprefetch")])
> be written in that case?  What should it use or clobber?
> I suppose ports have been known to use top-level CONST_INTs
> to implement a "nop" pattern, e.g. MIPS's:
> (define_insn "nop"
>   [(const_int 0)]
>   ""
>   "%(nop%)"
>   [(set_attr "type"	"nop")
>    (set_attr "mode"	"none")])
> but I think it would be cleaner to move _towards_ rather than
> away from UNSPECs in this case.

Fully agreed.  You certainly can't move away from UNSPEC if you have
multiple such patterns in your backend - it's not possible to
distinguish one USE from another.

Please revert that part of the documentation change.


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