TS 18661-1 defines a type femode_t to represent the set of dynamic
floating-point control modes (such as the rounding mode and trap
enablement modes), and functions fegetmode and fesetmode to manipulate
those modes (without affecting other state such as the raised
exception flags) and a corresponding macro FE_DFL_MODE.
This patch series implements those interfaces for glibc. This first
patch adds the architecture-independent pieces, the x86 and x86_64
implementations, and the <bits/fenv.h> and ABI baseline updates for
all architectures so glibc keeps building and passing the ABI tests on
all architectures. Subsequent patches add the fegetmode and fesetmode
implementations for other architectures.
femode_t is generally an integer type - the same type as fenv_t, or as
the single element of fenv_t where fenv_t is a structure containing a
single integer (or the single relevant element, where it has elements
for both status and control registers) - except where architecture
properties or consistency with the fenv_t implementation indicate
otherwise. FE_DFL_MODE follows FE_DFL_ENV in whether it's a magic
pointer value (-1 cast to const femode_t *), a value that can be
distinguished from valid pointers by its high bits but otherwise
contains a representation of the desired register contents, or a
pointer to a constant variable (the powerpc case; __fe_dfl_mode is
added as an exported constant object, an alias to __fe_dfl_env).
Note that where architectures (that share a register between control
and status bits) gain definitions of new floating-point control or
status bits in future, the implementations of fesetmode for those
architectures may need updating (depending on whether the new bits are
control or status bits and what the implementation does with
previously unknown bits), just like existing implementations of
<fenv.h> functions that take care not to touch reserved bits may need
updating when the set of reserved bits changes. (As any new bits are
outside the scope of ISO C, that's just a quality-of-implementation
issue for supporting them, not a conformance issue.)
As with fenv_t, femode_t should properly include any software DFP
rounding mode (and for both fenv_t and femode_t I'd consider that
fragment of DFP support appropriate for inclusion in glibc even in the
absence of the rest of libdfp; hardware DFP rounding modes should
already be included if the definitions of which bits are status /
control bits are correct).
Tested for x86_64, x86, mips64 (hard float, and soft float to test the
fallback version), arm (hard float) and powerpc (hard float, soft
float and e500). Other architecture versions are untested.
* math/fegetmode.c: New file.
* math/fesetmode.c: Likewise.
* sysdeps/i386/fpu/fegetmode.c: Likewise.
* sysdeps/i386/fpu/fesetmode.c: Likewise.
* sysdeps/x86_64/fpu/fegetmode.c: Likewise.
* sysdeps/x86_64/fpu/fesetmode.c: Likewise.
* math/fenv.h: Update comment on inclusion of <bits/fenv.h>.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (fegetmode): New function
declaration.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (fesetmode): Likewise.
* bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (femode_t): New
typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/aarch64/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/alpha/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/arm/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/hppa/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/ia64/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/m68k/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/microblaze/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/mips/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/nios2/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/powerpc/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (__fe_dfl_mode): New variable
declaration.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/s390/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/sh/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/sparc/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/tile/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* sysdeps/x86/fpu/bits/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
(femode_t): New typedef.
[__GLIBC_USE (IEC_60559_BFP_EXT)] (FE_DFL_MODE): New macro.
* manual/arith.texi (FE_DFL_MODE): Document macro.
(fegetmode): Document function.
(fesetmode): Likewise.
* math/Versions (fegetmode): New libm symbol at version
GLIBC_2.25.
(fesetmode): Likewise.
* math/Makefile (libm-support): Add fegetmode and fesetmode.
(tests): Add test-femode and test-femode-traps.
* math/test-femode-traps.c: New file.
* math/test-femode.c: Likewise.
* sysdeps/powerpc/fpu/fenv_const.c (__fe_dfl_mode): Declare as
alias for __fe_dfl_env.
* sysdeps/powerpc/nofpu/fenv_const.c (__fe_dfl_mode): Likewise.
* sysdeps/powerpc/powerpc32/e500/nofpu/fenv_const.c
(__fe_dfl_mode): Likewise.
* sysdeps/powerpc/Versions (__fe_dfl_mode): New libm symbol at
version GLIBC_2.25.
* sysdeps/nacl/libm.abilist: Update.
* sysdeps/unix/sysv/linux/aarch64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/alpha/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/arm/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/hppa/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/i386/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/ia64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/m68k/coldfire/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/m68k/m680x0/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/microblaze/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/nios2/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libm.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libm.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm-le.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libm.abilist:
Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/sh/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libm.abilist:
Likewise.
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libm.abilist:
Likewise.
* sysdeps/unix/sysv/linux/tile/tilepro/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.
On powerpc, floating-point environment macros are defined as pointers
to constants in the library that contain the bit-patterns of the
desired environment, instead of being magic constants cast to pointer
type.
For soft-float, the bit-patterns used for fenv_t are not laid out the
same as for hard-float. (e500 has a third layout used; that's not an
ABI issue because these values are only meaningful within a single
process, all of whose glibc libraries must come from the same build of
glibc.) While the __fe_dfl_env value for soft-float was appropriate
for the soft-float fenv_t representation, the other two constants had
the same bit-patterns as for hard-float. Those bit patterns had the
effect of having exceptions already raised, causing
math/test-fenv-return to fail; this patch fixes the patterns used.
(__fe_nonieee_env also had exceptions unmasked, though they should be
masked to match hard-float semantics. Since there is no separate
non-IEEE mode for soft-float, it's most appropriate for
__fe_nonieee_env to be the same as __fe_dfl_env; this patch makes it
an alias.)
Tested for powerpc-nofpu.
[BZ #17261]
* sysdeps/powerpc/nofpu/fenv_const.c (__fe_enabled_env): Change
value to 0.
(__fe_nonieee_env): Define as an alias for __fe_dfl_env.
