On Tue, Jul 13, 2021 at 7:48 AM Wang, Pengfei <pengfei.w...@intel.com> wrote: > > Hi H.J., > > Our LLVM implementation currently use %xmm0 for both _Complex's real part and > imaginary part. Do we have special reason to use two registers? > We are using one register on X64. Considering the performance, especially the > register pressure, should it be better to use one register for _Complex > _Float16 on 32 bits target?
x86-64 psABI is unrelated to i386 psABI. Using a pair of registers is more natural for complex _Float16. Since it is only used for function return value, I don't think there is a register pressure issue. > Thanks > Pengfei > > -----Original Message----- > From: H.J. Lu <hjl.to...@gmail.com> > Sent: Tuesday, July 13, 2021 10:26 PM > To: Wang, Pengfei <pengfei.w...@intel.com>; llvm-...@lists.llvm.org > Cc: Joseph Myers <jos...@codesourcery.com>; GCC Patches > <gcc-patches@gcc.gnu.org>; GNU C Library <libc-al...@sourceware.org>; IA32 > System V Application Binary Interface <ia32-...@googlegroups.com> > Subject: Re: [llvm-dev] [PATCH] Add optional _Float16 support > > On Mon, Jul 12, 2021 at 8:59 PM Wang, Pengfei <pengfei.w...@intel.com> wrote: > > > > > Return _Float16 and _Complex _Float16 values in %xmm0/%xmm1 registers. > > > > Can you please explain the behavior here? Is there difference between > > _Float16 and _Complex _Float16 when return? I.e., 1, In which case will > > _Float16 values return in both %xmm0 and %xmm1? > > 2, For a single _Float16 value, are both real part and imaginary part > > returned in %xmm0? Or returned in %xmm0 and %xmm1 respectively? > > Here is the v2 patch to add the missing _Float16 bits. The PDF file is at > > https://gitlab.com/x86-psABIs/i386-ABI/-/wikis/Intel386-psABI > > > Thanks > > Pengfei > > > > -----Original Message----- > > From: llvm-dev <llvm-dev-boun...@lists.llvm.org> On Behalf Of H.J. Lu > > via llvm-dev > > Sent: Friday, July 2, 2021 6:28 AM > > To: Joseph Myers <jos...@codesourcery.com> > > Cc: llvm-...@lists.llvm.org; GCC Patches <gcc-patches@gcc.gnu.org>; > > GNU C Library <libc-al...@sourceware.org>; IA32 System V Application > > Binary Interface <ia32-...@googlegroups.com> > > Subject: Re: [llvm-dev] [PATCH] Add optional _Float16 support > > > > On Thu, Jul 1, 2021 at 3:10 PM Joseph Myers <jos...@codesourcery.com> wrote: > > > > > > On Thu, 1 Jul 2021, H.J. Lu via Gcc-patches wrote: > > > > > > > 2. Return _Float16 and _Complex _Float16 values in %xmm0/%xmm1 > > > > registers. > > > > > > That restricts use of _Float16 to processors with SSE. Is that what > > > we want in the ABI, or should _Float16 be available with base 32-bit > > > x86 architecture features only, much like _Float128 and the decimal > > > FP types > > > > Yes, _Float16 requires XMM registers. > > > > > are? (If it is restricted to SSE, we can of course ensure relevant > > > libgcc functions are built with SSE enabled, and likewise in glibc > > > if that gains > > > _Float16 functions, though maybe with some extra complications to > > > get relevant testcases to run whenever possible.) > > > > > > > _Float16 functions in libgcc should be compiled with SSE enabled. > > > > BTW, _Float16 software emulation may require more than just SSE since we > > need to do _Float16 load and store with XMM registers. > > There is no 16bit load/store for XMM registers without AVX512FP16. > > > > -- > > H.J. > > _______________________________________________ > > LLVM Developers mailing list > > llvm-...@lists.llvm.org > > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > > > > -- > H.J. -- H.J.
