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*From*: Segher Boessenkool <segher at kernel dot crashing dot org>*To*: Tejas Joshi <tejasjoshi9673 at gmail dot com>*Cc*: gcc at gcc dot gnu dot org, joseph at codesourcery dot com, Martin Jambor <mjambor at suse dot cz>*Date*: Fri, 30 Aug 2019 15:35:25 -0500*Subject*: Re: Expansion of narrowing math built-ins into power instructions*References*: <20190822062503.GI31406@gate.crashing.org> <CACMrGjD9oR6jJrN+XJZYsEW+Oheo4uV2JRxm35KX326A07ayrQ@mail.gmail.com> <20190822095620.GK31406@gate.crashing.org> <ri6h867dcok.fsf@suse.cz> <mptimqmvqit.fsf@arm.com> <CACMrGjCeaPFVHh-chy+aFBHxYJOO0Q_fhkAZ52yUPFL4zLaSBQ@mail.gmail.com> <20190825164717.GO31406@gate.crashing.org> <CACMrGjAsrFSZQgbuaEVqBEnjrL2ANV1bHJwLRz4fKTSfWZETOw@mail.gmail.com> <20190826074211.GQ31406@gate.crashing.org> <CACMrGjBN-Un1-qMLdzdzaR3YRo05ukLm9cpyNzdm4vu346g6Gg@mail.gmail.com>

> > > > [ Please don't top-post ] (I delete everything under your signature, without looking, assuming you just forgot to). On Sat, Aug 31, 2019 at 12:48:42AM +0530, Tejas Joshi wrote: > > For ISA 2.07 (Power 8) you don't have IEEE128 at all, not in hardware > > that is. I don't know if we'll want fadd support in the emulation > > libraries ever; don't worry about it for now, anyway. > > What instructions would need to be expanded for FADDL (long double to > float) and DADDL (long double to double) on power8 (ISA 2.07) and > power9 (ISA 3.0) respectively, along with VSX? (Just as we expanded > FADD to fadds and xsaddsp for vsx). If long double is double, faddl is the same as fadd, and daddl is just normal addition. If long double is double-double, faddl can be done as fadd on the first double precision component of both args, and daddl is just normal addition of those. If long double is IEEE QP, then it is more interesting :-) daddl is xsaddqpo # add qp, with round to odd xscvqpdp # convert qp to dp faddl is xsaddqpo # add qp, with round to odd xscvqpdpo # convert qp to dp, with round to odd xsrsp # convert dp to sp (single precision numbers are stored in double precision format, but this is rounded as single precision) fadds is fadds ; :-) or xsaddsp Both faddl and daddl are the sequences for Power9. There are no instructions for QP format on Power8; see libgcc/config/rs6000/t-float128 for how support for the emulation QP math is built, if you are interested. Segher

**References**:**Re: Expansion of narrowing math built-ins into power instructions***From:*Segher Boessenkool

**Re: Expansion of narrowing math built-ins into power instructions***From:*Tejas Joshi

**Re: Expansion of narrowing math built-ins into power instructions***From:*Segher Boessenkool

**Re: Expansion of narrowing math built-ins into power instructions***From:*Martin Jambor

**Re: Expansion of narrowing math built-ins into power instructions***From:*Richard Sandiford

**Re: Expansion of narrowing math built-ins into power instructions***From:*Tejas Joshi

**Re: Expansion of narrowing math built-ins into power instructions***From:*Segher Boessenkool

**Re: Expansion of narrowing math built-ins into power instructions***From:*Tejas Joshi

**Re: Expansion of narrowing math built-ins into power instructions***From:*Segher Boessenkool

**Re: Expansion of narrowing math built-ins into power instructions***From:*Tejas Joshi

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