> -----Original Message----- > From: Richard Sandiford [mailto:rdsandif...@googlemail.com] > Sent: Monday, March 04, 2013 3:54 PM > To: Moore, Catherine > Cc: gcc-patches@gcc.gnu.org; Rozycki, Maciej > Subject: Re: FW: [PATCH] [MIPS] microMIPS gcc support > > "Moore, Catherine" <catherine_mo...@mentor.com> writes: > > Hi Richard, > - Predicates should always check the code though. E.g.: > > (define_predicate "umips_addius5_imm" > (and (match_code "const_int") > (match_test "IN_RANGE (INTVAL (op), -8, 7)"))) > > - In general, please try to make the names of the predicates as generic > as possible. There's nothing really add-specific about the predicate > above. Or microMIPS-specific either really: some of these predicates > are probably going to be useful for MIPS16 too. > > The existing MIPS16 functions follow the convention: > > "n" if negated (optional) > + "s" or "u" for signed vs. unsigned > + "imm" > + number of significant bits > + "_" > + multiplication factor or, er, "b" for "+1"... > > It might be nice to have a similar convention for microMIPS. > The choices there are a bit more exotic, so please feel free to > diverge from the MIPS16 one above; we can switch MIPS16 over once > the microMIPS one is settled. In fact, a new convention that's > compact enough to be used in both predicate and constraint names > would be great. E.g. for the umips_addius5_imm predicate above, > a name like "Ys5" would be easier to remember than "Zo"/"Yo".
How compact would you consider "compact enough"? I would need to change the existing "Y" constraints as well. Would YG --> Yvec0 be too long? I think trying to invent some convention with less than four letter will be difficult and even with four, I doubt it could be uniformly followed. I think we could get descriptive with four, however. Let me know what you think. > > That said，I realise things like umips_addiur2_imm_p are a bit > hard to describe this way and might need to stay instruction-specific. > > - We already have a "ks" constraint for the stack pointer. > > - I like the choice of "u" for M16_REGS. Kind of lucky that that letter's > still free. :-) As you've probably noticed though, we're running desparately > short of contraint letters, so if you also need names for other less > frequently-used classes, it might be better to use "k..." for those. > > Thanks, > Richard
