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The default sysdeps/ieee754 fma implementations rely on exceptions and rounding modes to achieve correct results through internal use of round-to-odd. Thus, glibc configurations without support for exceptions and rounding modes instead need to use implementations of fma based on soft-fp. At present, this is achieved via having implementation files in soft-fp/ that are #included by sysdeps files for each glibc configuration that needs them. In general this means such a configuration has its own s_fma.c and s_fmaf.c. TS 18661-1 adds functions that do an operation (+ - * / sqrt fma) on arguments wider than the return type, with a single rounding of the infinite-precision result to that return type. These are also naturally implemented using round-to-odd on platforms with hardware support for rounding modes and exceptions but lacking hardware support for these narrowing operations themselves. (Platforms that have direct hardware support for such narrowing operations include at least ia64, and Power ISA 2.07 or later, which I think means POWER8 or later.) So adding the remaining TS 18661-1 functions would mean at least six narrowing function implementations (fadd fsub fmul fdiv ffma fsqrt), with aliases for other types and further implementations in some configurations, that need to be overridden for configurations lacking hardware exceptions and rounding modes. Requiring all such configurations (currently seven of them) to have their own source files for all those functions seems undesirable. Thus, this patch adds a directory sysdeps/ieee754/soft-fp to contain libm function implementations based on soft-fp. This directory is then used via Implies from all the configurations that need it, so no more files need adding to every such configuration when adding more functions with soft-fp implementations. A configuration can still selectively #include a particular file from this directory if desired; thus, the MIPS #include of the fmal implementation is retained, since that's appropriate even for hard float (because long double is always implementated in software for MIPS64, so the soft-fp implementation of fmal is better than the ldbl-128 one). This also provides additional motivation for my recent patch removing --with-fp / --without-fp: previously there was no need for correct use of --without-fp for no-FPU ARM or SH3, and now we have autodetection nofpu/ sysdeps directories can be used by this patch for those configurations without imposing any new requirements on how glibc is configured. (The mips64/*/fpu/s_fma.c files added by this patch are needed to keep the dbl-64 version of fma for double, rather than the ldbl-128 one, used in that case.) Tested with build-many-glibcs.py that installed stripped shared libraries are unchanged by this patch. * soft-fp/fmadf4.c: Move to .... * sysdeps/ieee754/soft-fp/s_fma.c: ... here. * soft-fp/fmasf4.c: Move to .... * sysdeps/ieee754/soft-fp/s_fmaf.c: ... here. * soft-fp/fmatf4.c: Move to .... * sysdeps/ieee754/soft-fp/s_fmal.c: ... here. * sysdeps/ieee754/soft-fp/Makefile: New file. * sysdeps/arm/preconfigure.ac: Define with_fp_cond. * sysdeps/arm/preconfigure: Regenerated. * sysdeps/arm/nofpu/Implies: New file. * sysdeps/arm/s_fma.c: Remove file. * sysdeps/arm/s_fmaf.c: Likewise. * sysdeps/m68k/coldfire/nofpu/Implies: New file. * sysdeps/m68k/coldfire/nofpu/s_fma.c: Remove file. * sysdeps/m68k/coldfire/nofpu/s_fmaf.c: Likewise. * sysdeps/microblaze/Implies: Add ieee754/soft-fp. * sysdeps/microblaze/s_fma.c: Remove file. * sysdeps/microblaze/s_fmaf.c: Likewise. * sysdeps/mips/mips32/nofpu/Implies: New file. * sysdeps/mips/mips64/n32/fpu/s_fma.c: Likewise. * sysdeps/mips/mips64/n32/nofpu/Implies: Likewise. * sysdeps/mips/mips64/n64/fpu/s_fma.c: Likewise. * sysdeps/mips/mips64/n64/nofpu/Implies: Likewise. * sysdeps/mips/ieee754/s_fma.c: Remove file. * sysdeps/mips/ieee754/s_fmaf.c: Likewise. * sysdeps/mips/ieee754/s_fmal.c: Update include for move of fmal implementation. * sysdeps/nios2/Implies: Add ieee754/soft-fp. * sysdeps/nios2/s_fma.c: Remove file. * sysdeps/nios2/s_fmaf.c: Likewise. * sysdeps/sh/nofpu/Implies: New file. * sysdeps/sh/s_fma.c: Remove file. * sysdeps/sh/s_fmaf.c: Likewise. * sysdeps/tile/Implies: Add ieee754/soft-fp. * sysdeps/tile/s_fma.c: Remove file. * sysdeps/tile/s_fmaf.c: Likewise. |
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This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. The current GNU/Hurd support requires out-of-tree patches that will eventually be incorporated into an official GNU C Library release. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi hppa-*-linux-gnu Not currently functional without patches. i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu tilegx-*-linux-gnu tilepro-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.