Andreas Krebbel writes: > On 06/28/2016 04:16 PM, Jiong Wang wrote: > ... >> So my first impression is TARGET_LEGITIMATE_ADDRESS_P on s390 do need a >> fix here. The following draft patch fix this, my fix may be in >> correct as normally we will allow illegal constant offset if it's >> associated with virtual frame register before virtual register >> elimination, I don't know if that should be considered here. Also I >> don't know if such check should be constrainted under some architecture >> features. >> >> --- a/gcc/config/s390/s390.c >> +++ b/gcc/config/s390/s390.c >> @@ -4374,6 +4374,11 @@ s390_legitimate_address_p (machine_mode mode, rtx >> addr, bool strict) >> || REGNO_REG_CLASS (REGNO (ad.indx)) == ADDR_REGS)) >> return false; >> } >> + >> + if (ad.disp >> + && !s390_short_displacement (ad.disp)) >> + return false; >> + >> return true; >> } > > Whether short displacement is required or not depends on the instruction. We > always relied on reload > to take care of this. legitimate_address_p needs to accept the union of all > valid adresses on > S/390. That change probably would cause a severe performance regression. > >> Meanwhile I feel LRA might be too strict here, as we can't assume all >> address legitimized before lra, right? we still need to handle reload >> illegal address. While now, a reload of >> >> set (mem (reg + reg + offset)) regA >> >> (The offset is out of range that the inner address doesn't pass >> constraint check.) >> >> into >> >> regB <- reg + reg + offset >> (set (mem (regB)) regA) > > This is exactly what is supposed to happen in that case. All addresses which > might be invalid to be > used directly in an insn can be handled with load address or load address > relative long (+ secondary > reload for odd addresses). > >> is treate as spill after r237277, so I feel the following check in >> lra-constraints.c also needs a relax? >> >> if (no_regs_p && !(REG_P (op) && hard_regno[nop] < 0)) >> >> >> Comments?
I am testing a fix which teach LRA don't add spill cost if it's "offmemok". -- Regards, Jiong
