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.
GCC marked OABI obsolete in 4.7 and dropped it in 4.8. So the number
of people this is catching is shrinking every day. At this point,
it's not terribly useful, so just drop it.
This patch removes the configure test for working -z relro.
The use of -z relro in Makeconfig became unconditional with
commit 2e6ab1df44c412bb9d30b26a4d8a679150a7e375
Author: Ulrich Drepper <drepper@redhat.com>
Date: Sat Oct 28 06:44:04 2006 +0000
Remove conditional code which now is unnecessary.
(commit reference from git://repo.or.cz/glibc/history), so since then
the configure test has not controlled anything about how glibc is
built - simply about whether configure succeeds and allows a build to
be attempted. The test for whether the option did something useful
(as opposed to whether it exists - which we can certainly just assume
by now) was originally added in
<https://sourceware.org/ml/libc-hacker/2004-09/msg00069.html> to
disable the option in a case when it did nothing useful on ia64 (as a
result of something deliberate in the linker on ia64). Since 2006
that disabling has been of no effect, and given that the current test
does not set libc_relro_required for ia64, it does nothing whatever
useful for the original motivating case. Also at around the same time
in 2006 the test was made to give an error for missing or broken -z
relro support on various architectures.
So effectively all the test does now is verify that, on certain
architectures, the linker has not been changed deliberately to make
the option ineffective. I see no apparent reason why such a change
should be expected, or why the build should be stopped if it were to
be made (any more than we disallow build on ia64); I think we can
trust binutils patch review to point out the consequences of any
change to COMMONPAGESIZE setting. The only thing that might now make
sense would be disabling the -z relro use on an architecture-specific
basis if there were an architecture-specific reason to consider that
to make sense; it would be for the ia64 maintainer to decide if that
makes sense for ia64 at present, but I think that could be done
through sysdeps Makefiles - no special configure tests needed.
Tested for x86_64 that this patch makes no change to the installed
shared libraries.
Together with
<https://sourceware.org/ml/libc-alpha/2014-06/msg00788.html> (pending
review) this substantially eliminates architecture-specific cases from
architecture-independent configure.ac files. There remains an i386
case in sysdeps/mach/hurd/configure.ac that should properly move to
the i386 subdirectory. (There are also OS-specific cases outside
OS-specific directories; in principle I think should should also
move.)
* configure.ac (libc_commonpagesize): Remove variable.
(libc_relro_required): Likewise.
(libc_cv_z_relro): Remove configure test.
* configure: Regenerated.
* sysdeps/aarch64/preconfigure (libc_commonpagesize): Do not set
variable.
(libc_relro_required): Likewise.
* sysdeps/alpha/preconfigure (libc_commonpagesize): Likewise.
(libc_relro_required): Likewise.
* sysdeps/arm/preconfigure.ac (libc_commonpagesize): Likewise.
(libc_relro_required): Likewise.
* sysdeps/arm/preconfigure: Regenerated.
* sysdeps/ia64/preconfigure: Remove file.
* sysdeps/tile/preconfigure (libc_commonpagesize): Do not set
variable.
(libc_relro_required): Likewise.
Set values for libc_commonpagesize and libc_relro_required for the
ARM port to enable relro by default and suppress a warning at
configure time.
ChangeLog:
2014-05-09 Will Newton <will.newton@linaro.org>
* sysdeps/arm/preconfigure.ac: Set libc_commonpagesize
and libc_relro_required for ARM.
* sysdeps/arm/preconfigure: Regenerate.
I've moved the ARM port from ports to the main sysdeps hierarchy.
Beyond the README update, the move of the files was simply
git mv ports/sysdeps/arm sysdeps/arm
git mv ports/sysdeps/unix/arm sysdeps/unix/arm
git mv ports/sysdeps/unix/sysv/linux/arm sysdeps/unix/sysv/linux/arm
and in addition to the ChangeLog entries here, I put a note at the top
of ports/ChangeLog.arm similar to that at the top of
ChangeLog.powerpc. There is deliberately no NEWS change, as I think
it makes the most sense to put in a general note above all ports
having moved if we can achieve that for 2.20.
Tested that disassembly of installed shared libraries for arm is the
same before and after this patch, except for data (not instructions)
in ld.so (there are assertions in sysdeps/arm/dl-machine.h, and the
path by which that file is found, and so by which it appears in the
assertion message, changes as a result of the move).
* sysdeps/arm: Move directory from ports/sysdeps/arm.
* sysdeps/unix/arm: Move directory from ports/sysdeps/unix/arm.
* sysdeps/unix/sysv/linux/arm: Move directory from
ports/sysdeps/unix/sysv/linux/arm.
* README: Update listing for arm-*-linux-gnueabi.
ports/ChangeLog.arm:
* sysdeps/arm: Move directory to ../sysdeps/arm.
* sysdeps/unix/arm: Move directory to ../sysdeps.arm.
* sysdeps/unix/sysv/linux/arm: Move directory to
../sysdeps/unix/sysv/linux/arm.
