Richard Biener <richard.guent...@gmail.com> writes: > On Fri, Sep 13, 2013 at 10:33 AM, Richard Sandiford > <rdsandif...@googlemail.com> wrote: >> Richard Biener <richard.guent...@gmail.com> writes: >>>> Yeah. I don't think it makes sense to canonise PSI to 32 bits when we >>>> know it has fewer than 32 bits. It's still going to be wrong, and will >>>> still defeat one of the main purposes of canonical constants, which is >>>> to make equality obvious. E.g. we'd still treat PSI constants >>>> >>>> (const_int 0x...ff80000000) >>>> >>>> and >>>> >>>> (const_int 0x...ffc0000000) >>>> >>>> as different, even though they're both zero for a 24-bit PSI. >>>> >>>> This partial integer mode stuff is just a big hack. Like you say, >>>> we can only really do something sensible if we know what the real >>>> precision is. >>>> >>>> So I'd rather leave things as they are for this series. The precision >>>> effectively becomes 65535 thanks to the underlying unsigned short array, >>>> so like you say, trunc_int_for_mode is a no-op for partial modes. >>>> Changing GEN_INT to gen_int_mode shouldn't make any difference. >>>> >>>> What do you think about the patch for CC modes? >>> >>> I wonder if we can do without changing gen_int_mode by fixing the callers >>> like you did for cse.c (that patch is ok). >> >> But the point of the gen_int_mode patch is that (for better or worse) >> CONST_INT is the right choice of rtx for constant CC values. I'd like >> eventually to get rid of all GEN_INT callers, and some of those callers >> will sometimes or always be handling CC modes. This would then crop up >> again in a legitimate context. >> >> IMO, cse.c was buggy not because it was trying to generate a CCmode >> CONST_INT, but because anchor optimisations involve addition, which >> isn't defined for CC modes. >> >> I think gen_int_mode should do the right thing for all CONST_INT modes. >> gen_int_mode (X, MODE) should really be the moral equivalent of >> gen_rtx_CONST_INT (MODE, X), despite the confusingly-swapped parameters. > > Yeah, ok. But the GEN_INT changes have already uncovered quite some bugs > so maybe let us discover a few more CCmode bugs first? ...
OK, sounds fair. I'll hold off the gen_int_mode change until I have legitimate use. I went ahead and applied the cse.c change. Thanks, Richard
