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This patch fixes a soft-fp corner case I previously noted in <https://sourceware.org/ml/libc-alpha/2013-10/msg00349.html>: when trapping on underflow is enabled, extensions of subnormals from XFmode to TFmode need to signal underflow because the result is tiny (but exact, so the underflow flag is not raised unless trapping is enabled). To avoid any excess initialization or tests for other cases of floating-point extensions, a new FP_INIT_TRAPPING_EXCEPTIONS is added that does the initialization required for this particular case (more than FP_INIT_EXCEPTIONS, less than FP_INIT_ROUNDMODE, in general), and FP_NO_EXACT_UNDERFLOW is added to stub out FP_TRAPPING_EXCEPTIONS tests for those cases of extensions where the test would be dead code, to avoid any uninitialized variable warnings. As the relevant case only applies in libgcc, not to any use of soft-fp in glibc, there is no bug report in Bugzilla and no non-default definitions of FP_INIT_TRAPPING_EXCEPTIONS are added by the patch. A testcase will be added to GCC as part of an update of soft-fp in libgcc once this patch is in libc. Tested for powerpc-nofpu that the disassembly of installed shared libraries is unchanged by this patch. Bootstrapped GCC with updated soft-fp with no regressions on x86_64-unknown-linux-gnu and verified that a test of the relevant case passes where it failed before. * soft-fp/op-common.h (FP_EXTEND): When a subnormal input produces a subnormal result, set the underflow exception if trapping on underflow is enabled. * soft-fp/soft-fp.h (FP_INIT_TRAPPING_EXCEPTIONS): New macro. (FP_INIT_EXCEPTIONS): Default to FP_INIT_TRAPPING_EXCEPTIONS. [FP_NO_EXACT_UNDERFLOW] (FP_TRAPPING_EXCEPTIONS): Undefine and redefine to 0. * soft-fp/extenddftf2.c (FP_NO_EXACT_UNDERFLOW): Define. * soft-fp/extendsfdf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. * soft-fp/extendsftf2.c (FP_NO_EXACT_UNDERFLOW): Likewise. * soft-fp/extendxftf2.c (__extendxftf2): Use FP_INIT_TRAPPING_EXCEPTIONS instead of FP_INIT_ROUNDMODE. |
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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 2.6.32 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., 2000-2013, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.