[PATCH v1 1/2] x86: Add defines / utilities for making ISA specific x86 builds
Noah Goldstein
goldstein.w.n@gmail.com
Fri Jun 17 20:13:05 GMT 2022
On Fri, Jun 17, 2022 at 12:30 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Fri, Jun 17, 2022 at 12:13 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Thu, Jun 16, 2022 at 8:50 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > 1. Factor out some of the ISA level defines in isa-level.c to
> > > standalone header isa-level.h
> > >
> > > 2. Add new headers with ISA level dependent macros for handling
> > > ifuncs.
> > >
> > > Note, this file does not change any code.
> > >
> > > Tested with and without multiarch on x86_64 for ISA levels:
> > > {generic, x86-64-v2, x86-64-v3, x86-64-v4}
> > > ---
> > > sysdeps/x86/isa-level.c | 17 +---
> > > sysdeps/x86/isa-level.h | 70 +++++++++++++
> > > sysdeps/x86_64/isa-default-include.h | 49 +++++++++
> > > sysdeps/x86_64/multiarch/isa-ifunc-macros.h | 106 ++++++++++++++++++++
> > > 4 files changed, 230 insertions(+), 12 deletions(-)
> > > create mode 100644 sysdeps/x86/isa-level.h
> > > create mode 100644 sysdeps/x86_64/isa-default-include.h
> > > create mode 100644 sysdeps/x86_64/multiarch/isa-ifunc-macros.h
> > >
> > > diff --git a/sysdeps/x86/isa-level.c b/sysdeps/x86/isa-level.c
> > > index 09cd72ab20..8e899bf64b 100644
> > > --- a/sysdeps/x86/isa-level.c
> > > +++ b/sysdeps/x86/isa-level.c
> > > @@ -26,38 +26,31 @@
> > > <https://www.gnu.org/licenses/>. */
> > >
> > > #include <elf.h>
> > > -
> > > +#include <sysdeps/x86/isa-level.h>
> > > /* ELF program property for x86 ISA level. */
> > > #ifdef INCLUDE_X86_ISA_LEVEL
> > > -# if defined __SSE__ && defined __SSE2__
> > > +# if __X86_ISA_V1
> >
> > #if MINIMUM_X86_ISA_LEVEL >= 1
> >
> > > /* NB: ISAs, excluding MMX, in x86-64 ISA level baseline are used. */
> > > # define ISA_BASELINE GNU_PROPERTY_X86_ISA_1_BASELINE
> > > # else
> > > # define ISA_BASELINE 0
> > > # endif
> > >
> > > -# if ISA_BASELINE && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
> > > - && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ \
> > > - && defined __SSE3__ && defined __SSSE3__ && defined __SSE4_1__ \
> > > - && defined __SSE4_2__
> > > +# if __X86_ISA_V2
> >
> > #if MINIMUM_X86_ISA_LEVEL >= 2
> >
> > > /* NB: ISAs in x86-64 ISA level v2 are used. */
> > > # define ISA_V2 GNU_PROPERTY_X86_ISA_1_V2
> > > # else
> > > # define ISA_V2 0
> > > # endif
> > >
> > > -# if ISA_V2 && defined __AVX__ && defined __AVX2__ && defined __F16C__ \
> > > - && defined __FMA__ && defined __LZCNT__ && defined HAVE_X86_MOVBE \
> > > - && defined __BMI__ && defined __BMI2__
> > > +# if __X86_ISA_V3
> >
> > #if MINIMUM_X86_ISA_LEVEL >= 3
> >
> > > /* NB: ISAs in x86-64 ISA level v3 are used. */
> > > # define ISA_V3 GNU_PROPERTY_X86_ISA_1_V3
> > > # else
> > > # define ISA_V3 0
> > > # endif
> > >
> > > -# if ISA_V3 && defined __AVX512F__ && defined __AVX512BW__ \
> > > - && defined __AVX512CD__ && defined __AVX512DQ__ \
> > > - && defined __AVX512VL__
> > > +# if __X86_ISA_V4
> >
> > #if MINIMUM_X86_ISA_LEVEL >= 4
> >
> > > /* NB: ISAs in x86-64 ISA level v4 are used. */
> > > # define ISA_V4 GNU_PROPERTY_X86_ISA_1_V4
> > > # else
> > > diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
> > > new file mode 100644
> > > index 0000000000..ed696ae8eb
> > > --- /dev/null
> > > +++ b/sysdeps/x86/isa-level.h
> > > @@ -0,0 +1,70 @@
> > > +/* Header defining the minimum x86 ISA level
> > > + Copyright (C) 2020-2022 Free Software Foundation, Inc.
> >
> > Just 2022.
> >
> > > + This file is part of the GNU C Library.
> > > +
> > > + The GNU C Library is free software; you can redistribute it and/or
> > > + modify it under the terms of the GNU Lesser General Public
> > > + License as published by the Free Software Foundation; either
> > > + version 2.1 of the License, or (at your option) any later version.
> > > +
> > > + In addition to the permissions in the GNU Lesser General Public
> > > + License, the Free Software Foundation gives you unlimited
> > > + permission to link the compiled version of this file with other
> > > + programs, and to distribute those programs without any restriction
> > > + coming from the use of this file. (The Lesser General Public
> > > + License restrictions do apply in other respects; for example, they
> > > + cover modification of the file, and distribution when not linked
> > > + into another program.)
> > > +
> > > + The GNU C Library is distributed in the hope that it will be useful,
> > > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > > + Lesser General Public License for more details.
> > > +
> > > + You should have received a copy of the GNU Lesser General Public
> > > + License along with the GNU C Library; if not, see
> > > + <https://www.gnu.org/licenses/>. */
> > > +
> > > +#ifndef _ISA_LEVEL_H
> > > +#define _ISA_LEVEL_H
> > > +
> > > +# if defined __SSE__ && defined __SSE2__
> > > +/* NB: ISAs, excluding MMX, in x86-64 ISA level baseline are used. */
> > > +# define __X86_ISA_V1 1
> > > +# else
> > > +# define __X86_ISA_V1 0
> > > +# endif
> > > +
> > > +# if __X86_ISA_V1 && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
> > > + && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ \
> > > + && defined __SSE3__ && defined __SSSE3__ && defined __SSE4_1__ \
> > > + && defined __SSE4_2__
> > > +/* NB: ISAs in x86-64 ISA level v2 are used. */
> > > +# define __X86_ISA_V2 1
> > > +# else
> > > +# define __X86_ISA_V2 0
> > > +# endif
> > > +
> > > +# if __X86_ISA_V2 && defined __AVX__ && defined __AVX2__ && defined __F16C__ \
> > > + && defined __FMA__ && defined __LZCNT__ && defined HAVE_X86_MOVBE \
> > > + && defined __BMI__ && defined __BMI2__
> > > +/* NB: ISAs in x86-64 ISA level v3 are used. */
> > > +# define __X86_ISA_V3 1
> > > +# else
> > > +# define __X86_ISA_V3 0
> > > +# endif
> > > +
> > > +# if __X86_ISA_V3 && defined __AVX512F__ && defined __AVX512BW__ \
> > > + && defined __AVX512CD__ && defined __AVX512DQ__ \
> > > + && defined __AVX512VL__
> > > +/* NB: ISAs in x86-64 ISA level v4 are used. */
> > > +# define __X86_ISA_V4 1
> > > +# else
> > > +# define __X86_ISA_V4 0
> > > +# endif
> > > +
> > > +#define __X86_ISA_LEVEL \
> > > + (__X86_ISA_V1 + __X86_ISA_V2 + __X86_ISA_V3 + __X86_ISA_V4)
> > > +
> >
> > We have isa.h to define MINIMUM_ISA. I think this file should define
> > MINIMUM_X86_ISA_LEVEL.
> >
> > > +#endif
> > > diff --git a/sysdeps/x86_64/isa-default-include.h b/sysdeps/x86_64/isa-default-include.h
> > > new file mode 100644
> > > index 0000000000..d3091340af
> > > --- /dev/null
> > > +++ b/sysdeps/x86_64/isa-default-include.h
> >
> > isa-default-impl.h? since this header file includes the default implementation.
> >
> > > @@ -0,0 +1,49 @@
> > > +/* Utility for including proper default function based on ISA level
> >
> > Include the default implementation based on the minimum ISA level.
> >
> > > + Copyright (C) 2021-2022 Free Software Foundation, Inc.
> >
> > Just 2022.
> >
> > > + This file is part of the GNU C Library.
> > > +
> > > + The GNU C Library is free software; you can redistribute it and/or
> > > + modify it under the terms of the GNU Lesser General Public
> > > + License as published by the Free Software Foundation; either
> > > + version 2.1 of the License, or (at your option) any later version.
> > > +
> > > + The GNU C Library is distributed in the hope that it will be useful,
> > > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > > + Lesser General Public License for more details.
> > > +
> > > + You should have received a copy of the GNU Lesser General Public
> > > + License along with the GNU C Library; if not, see
> > > + <https://www.gnu.org/licenses/>. */
> > > +
> > > +#include <isa-level.h>
> > > +
> > > +#ifndef DEFAULT_V1
> >
> > ISA_DEFAULT_IMPL_V1
> >
> > > +# error "Must have at least ISA V1 Version"
> >
> > Must have at least ISA V1 implementation
> >
> > > +#endif
> > > +
> > > +#ifndef DEFAULT_V2
> > > +# define DEFAULT_V2 DEFAULT_V1
> > > +#endif
> > > +
> > > +#ifndef DEFAULT_V3
> > > +# define DEFAULT_V3 DEFAULT_V2
> > > +#endif
> > > +
> > > +#ifndef DEFAULT_V4
> > > +# define DEFAULT_V4 DEFAULT_V3
> > > +#endif
> > > +
> > > +#define IS_DEFAULT_INCLUDE
> >
> > We can remove IS_DEFAULT_INCLUDE and
> > check ISA_DEFAULT_IMPL instead.
> >
> > > +
> > > +#if __X86_ISA_LEVEL == 1
> >
> > #if MINIMUM_X86_ISA_LEVEL == 1
> >
> > > +# include DEFAULT_V1
> >
> > # define ISA_DEFAULT_IMPL ISA_DEFAULT_IMPL_V1
> >
> > > +#elif __X86_ISA_LEVEL == 2
> > > +# include DEFAULT_V2
> > > +#elif __X86_ISA_LEVEL == 3
> > > +# include DEFAULT_V3
> > > +#elif __X86_ISA_LEVEL == 4
> > > +# include DEFAULT_V4
> >
> > # define ISA_DEFAULT_IMPL ISA_DEFAULT_IMPL_V4
> >
> > > +#else
> > > +# error "Unsupport ISA Level!"
> > > +#endif
> >
> > #include ISA_DEFAULT_IMPL
> >
> > > diff --git a/sysdeps/x86_64/multiarch/isa-ifunc-macros.h b/sysdeps/x86_64/multiarch/isa-ifunc-macros.h
> > > new file mode 100644
> > > index 0000000000..c24f2ab655
> > > --- /dev/null
> > > +++ b/sysdeps/x86_64/multiarch/isa-ifunc-macros.h
> > > @@ -0,0 +1,106 @@
> > > +/* Common ifunc selection utils
> > > + All versions must be listed in ifunc-impl-list.c.
> > > + Copyright (C) 2017-2022 Free Software Foundation, Inc.
> > > + This file is part of the GNU C Library.
> > > +
> > > + The GNU C Library is free software; you can redistribute it and/or
> > > + modify it under the terms of the GNU Lesser General Public
> > > + License as published by the Free Software Foundation; either
> > > + version 2.1 of the License, or (at your option) any later version.
> > > +
> > > + The GNU C Library is distributed in the hope that it will be useful,
> > > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > > + Lesser General Public License for more details.
> > > +
> > > + You should have received a copy of the GNU Lesser General Public
> > > + License along with the GNU C Library; if not, see
> > > + <https://www.gnu.org/licenses/>. */
> > > +
> > > +#include <init-arch.h>
> > > +#include <isa-level.h>
> > > +
> > > +#define OPTIMIZE_DECL(...) \
> > > + extern __typeof (REDIRECT_NAME) OPTIMIZE (__VA_ARGS__) attribute_hidden;
> > > +
> > > +#define OPTIMIZE_DECL1(...) \
> > > + extern __typeof (REDIRECT_NAME) OPTIMIZE1 (__VA_ARGS__) attribute_hidden;
> > > +
> > > +/* Only include at the level of the build ISA or better. I.e if built
> >
> > minimum build ISA level
> >
> > > + with ISA=V1, then include all implementations. On the other hand if
> > > + built with ISA=V3 only include V3/V4 implementations. If there is
> > > + not implementation at or above the build ISA level, then include
> >
> > no implementation at or above the minimum build ISA level.
> >
> > > + the highest ISA level implementation. */
> > > +#if __X86_ISA_LEVEL <= 4
> > > +# define X86_IFUNC_IMPL_ADD_V4(...) IFUNC_IMPL_ADD (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE_V4(...) return OPTIMIZE (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE1_V4(...) return OPTIMIZE1 (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE_V4(...) OPTIMIZE_DECL (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE1_V4(...) OPTIMIZE_DECL1 (__VA_ARGS__)
> >
> > These macros should be added to <init-arch.h> instead. I don't
> > think DECLARE_X86_OPTIMIZE_VN is necessary since unused
> > declarations are OK.
>
> Its not unused declaration is declaration of function that doesn't
> exist.
>
> But if can remove will do so for V2.
> >
> > > +#endif
> > > +#if __X86_ISA_LEVEL <= 3
> > > +# define X86_IFUNC_IMPL_ADD_V3(...) IFUNC_IMPL_ADD (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE_V3(...) return OPTIMIZE (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE1_V3(...) return OPTIMIZE1 (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE_V3(...) OPTIMIZE_DECL (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE1_V3(...) OPTIMIZE_DECL1 (__VA_ARGS__)
> > > +#endif
> > > +#if __X86_ISA_LEVEL <= 2
> > > +# define X86_IFUNC_IMPL_ADD_V2(...) IFUNC_IMPL_ADD (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE_V2(...) return OPTIMIZE (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE1_V2(...) return OPTIMIZE1 (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE_V2(...) OPTIMIZE_DECL (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE1_V2(...) OPTIMIZE_DECL1 (__VA_ARGS__)
> > > +#endif
> > > +#if __X86_ISA_LEVEL <= 1
> > > +# define X86_IFUNC_IMPL_ADD_V1(...) IFUNC_IMPL_ADD (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE_V1(...) return OPTIMIZE (__VA_ARGS__)
> > > +# define return_X86_OPTIMIZE1_V1(...) return OPTIMIZE1 (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE_V1(...) OPTIMIZE_DECL (__VA_ARGS__)
> > > +# define DECLARE_X86_OPTIMIZE1_V1(...) OPTIMIZE_DECL1 (__VA_ARGS__)
> > > +#endif
> > > +
> > > +#ifndef return_X86_OPTIMIZE_V4
> > > +# define X86_IFUNC_IMPL_ADD_V4(...)
> > > +# define return_X86_OPTIMIZE_V4(...) (void) (0)
> > > +# define return_X86_OPTIMIZE1_V4(...) (void) (0)
> > > +# define DECLARE_X86_OPTIMIZE_V4(...)
> > > +# define DECLARE_X86_OPTIMIZE1_V4(...)
> > > +#endif
> > > +#ifndef return_X86_OPTIMIZE_V3
> > > +# define X86_IFUNC_IMPL_ADD_V3(...)
> > > +# define return_X86_OPTIMIZE_V3(...) (void) (0)
> > > +# define return_X86_OPTIMIZE1_V3(...) (void) (0)
> > > +# define DECLARE_X86_OPTIMIZE_V3(...)
> > > +# define DECLARE_X86_OPTIMIZE1_V3(...)
> > > +#endif
> > > +#ifndef return_X86_OPTIMIZE_V2
> > > +# define X86_IFUNC_IMPL_ADD_V2(...)
> > > +# define return_X86_OPTIMIZE_V2(...) (void) (0)
> > > +# define return_X86_OPTIMIZE1_V2(...) (void) (0)
> > > +# define DECLARE_X86_OPTIMIZE_V2(...)
> > > +# define DECLARE_X86_OPTIMIZE1_V2(...)
> > > +#endif
> > > +#ifndef return_X86_OPTIMIZE_V1
> > > +# define X86_IFUNC_IMPL_ADD_V1(...)
> > > +# define return_X86_OPTIMIZE_V1(...) (void) (0)
> > > +# define return_X86_OPTIMIZE1_V1(...) (void) (0)
> > > +# define DECLARE_X86_OPTIMIZE_V1(...)
> > > +# define DECLARE_X86_OPTIMIZE1_V1(...)
> > > +#endif
> > > +
> > > +#define DECLARE_X86_OPTIMIZE_FORCE(...) OPTIMIZE_DECL (__VA_ARGS__)
> > > +#define return_X86_OPTIMIZE_FORCE(...) return OPTIMIZE (__VA_ARGS__)
> > > +#define X86_IFUNC_IMPL_ADD_FORCE(...) IFUNC_IMPL_ADD (__VA_ARGS__)
> >
> > These are unused.
>
> Think will be used for strcspn/strspn/strpbrk but can drop for now.
> >
> > > +#if __X86_ISA_LEVEL == 1
> > > +# define X86_OPTIMIZE_FALLBACK(v1, ...) OPTIMIZE (v1)
> > > +#elif __X86_ISA_LEVEL == 2
> > > +# define X86_OPTIMIZE_FALLBACK(v1, v2, ...) OPTIMIZE (v2)
> > > +#elif __X86_ISA_LEVEL == 3
> > > +# define X86_OPTIMIZE_FALLBACK(v1, v2, v3, ...) OPTIMIZE (v3)
> > > +#elif __X86_ISA_LEVEL == 4
> > > +# define X86_OPTIMIZE_FALLBACK(v1, v2, v3, v4) OPTIMIZE (v4)
> > > +#else
> > > +# error "Unsupported ISA Level"
> > > +#endif
> > > --
> > > 2.34.1
> >
> > We can avoid X86_OPTIMIZE_FALLBACK by
> >
> > 1. Check the minimum ISA level IFUNC selector.
> > 2. Turn return_X86_OPTIMIZE_VN into __builtin_unreachable ()
> > when unused.
>
> I think there are some edge cases we may miss. I.e an ISA v3 implementation
> that also has prefer_novzeroupper. It is still correct to use avx2 impl with
> vzeroupper but we will fail in the ifunc preference.
>
> All other suggestions will fix for v2.
>
>
> >
> > Another issue. With AVX available, IFUNC selector may
> > prefer SSE version when AVX_Fast_Unaligned_Load or
> > Prefer_No_VZEROUPPER isn't set. This happens for memmove.
> > We have the default implementation without IFUNC and the
> > best implementation with IFUNC. They may not be the
> > same.
We won't have SSE built in that case. Think we are going to be forced
to just eat the AVX implementation in that case.
> >
> > --
> > H.J.
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