On Mon, Sep 7, 2020 at 10:46 AM Qian, Jianhua <qia...@cn.fujitsu.com> wrote: > > Hi Richard > > > -----Original Message----- > > From: Richard Biener <richard.guent...@gmail.com> > > Sent: Monday, September 7, 2020 3:41 PM > > To: Qian, Jianhua/钱 建华 <qia...@cn.fujitsu.com> > > Cc: gcc@gcc.gnu.org > > Subject: Re: A problem with one instruction multiple latencies and pipelines > > > > On Mon, Sep 7, 2020 at 8:10 AM Qian, Jianhua <qia...@cn.fujitsu.com> wrote: > > > > > > Hi > > > > > > I'm adding a new machine model. I have a problem when writing the > > "define_insn_reservation" for instruction scheduling. > > > How to write the "define_insn_reservation" for one instruction that there > > > are > > different latencies and pipelines according to parameter. > > > > > > For example, the ADD (shifted register) instruction in a64fx > > > > > > Instruction Option Latency > > Pipeline > > > ADD (shifted register) <amount> = 0 1 EX* > > | EAG* > > > <amount> = [1-4] && <shift>=LSL 1+1 > > (EXA + EXA) | (EXB + EXB) > > > 2+1 (EXA > > + EXA) | (EXB + EXB) > > > > > > In aarch64.md ADD (shifted register) instruction is defined as following． > > > (define_insn "*add_<shift>_<mode>" > > > [(set (match_operand:GPI 0 "register_operand" "=r") > > > (plus:GPI (ASHIFT:GPI (match_operand:GPI 1 "register_operand" > > "r") > > > (match_operand:QI 2 > > "aarch64_shift_imm_<mode>" "n")) > > > (match_operand:GPI 3 "register_operand" "r")))] > > > "" > > > "add\\t%<w>0, %<w>3, %<w>1, <shift> %2" > > > [(set_attr "type" "alu_shift_imm")] > > > ) > > > > > > It could not be distinguished by the type "alu_shift_imm" when writing > > "define_insn_reservation" for ADD (shifted register). > > > What should I do? > > > > Just a guess - I'm not very familiar with the pipeline modeling, you > > probably > > need to expose two alternatives so you can assign a different type to the > > second > > one. > I'm considering such method, > but if I do that I'm afraid it has side effects on other machine models of > aarch64 series. > Some instructions' definition will be changed in aarch64.md file. > > > Other than that modeling the more restrictive (or permissive?) variant might > > work good enough in practice. > Is your mean that an approximate modeling is good enough?
Yes. > > a64fx is probably out-of-order anyway. > Yes, a64fx is an out-of-order architecture. > > Regards > Qian > > > > > Richard. > > > > > Regards > > > Qian > > > > > > > > > > > > > >
