As previously discussed
<https://sourceware.org/ml/libc-alpha/2013-10/msg00345.html>, it would
be desirable to be able to use the same version of the soft-fp code in
the Linux kernel as well as in glibc and libgcc (instead of an old
version in the kernel that's missing ten years of bug fixes,
performance improvements and new features), and to that end it is
useful to add to glibc's copy features in the kernel's copy, even when
they are not directly useful in glibc.
To that end, this patch adds one of those features: support for more
precise "invalid" exceptions describing the particular kind of invalid
operation. These are relevant for powerpc emulation, and are also as
described in IEEE 754-2008 as sub-exceptions.
The set of sub-exceptions here is the union of those supported on
powerpc and those from IEEE 754-2008 (the former adds a distinction
between 0/0 and Inf/Inf; the latter adds a distinction between Inf*0
from multiplication and the same from fma). This includes
sub-exceptions for sqrt, conversions to integer and comparisons that
are not supported in the kernel; I see no obvious reason for these
being missing from the kernel support, given that they are supported
on powerpc so accurate powerpc emulation should generate them.
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.
* soft-fp/soft-fp.h (FP_EX_INVALID_SNAN): New macro.
(FP_EX_INVALID_IMZ): Likewise.
(FP_EX_INVALID_IMZ_FMA): Likewise.
(FP_EX_INVALID_ISI): Likewise.
(FP_EX_INVALID_ZDZ): Likewise.
(FP_EX_INVALID_IDI): Likewise.
(FP_EX_INVALID_SQRT): Likewise.
(FP_EX_INVALID_CVI): Likewise.
(FP_EX_INVALID_VC): Likewise.
* soft-fp/op-common.h (_FP_UNPACK_CANONICAL): Specify more precise
"invalid" exceptions.
(_FP_CHECK_SIGNAN_SEMIRAW): Likewise.
(_FP_ADD_INTERNAL): Likewise.
(_FP_MUL): Likewise.
(_FP_FMA): Likewise.
(_FP_DIV): Likewise.
(_FP_CMP_CHECK_NAN): Likewise.
(_FP_SQRT): Likewise.
(_FP_TO_INT): Likewise.
(FP_EXTEND): Likewise.
Continuing the addition of soft-fp features used in the Linux kernel,
this patch adds soft-fp support for FP_DENORM_ZERO (flushing input
subnormal operands to zero of the same sign).
There are some differences from the kernel version. In the kernel,
the "inexact" exception is set when flushing to zero. This does not
appear to match the documented semantics for either of the
architectures (alpha and sh) for which the kernel uses FP_DENORM_ZERO,
so this patch does not set "inexact" in this case. More operations
now use raw or semi-raw unpacking for optimization than did in the
ten-year-old soft-fp version in the kernel, so checks of
FP_DENORM_ZERO are inserted in those operations. They are also
inserted for comparisons (which already used raw unpacking in the old
version) as I believe that's the correct thing to do when input
subnormals are flushed to zero. They are *not* inserted for _FP_NEG.
(If any processors do flush input subnormals to zero for negation, or
otherwise vary from the rules implemented when FP_DENORM_ZERO is set,
further macros for sfp-machine.h to control this may need to be
added.)
Although the addition for comparisons will cause FP_EX_DENORM to be
set in this case, it still won't be set for comparisons involving
subnormals when not flushed to zero. It's quite possible that
accurate emulation of processors that have such an exception for
subnormal operands will require further changes relating to when
FP_EX_DENORM is set (in general, the support for things defined by
IEEE should be considered more reliable and mature than the support
for things outside the scope of IEEE floating point).
Although some processors also have a mode for abrupt underflow -
producing zeroes instead of output subnormals - there is no such mode
in the kernel's soft-fp, so no such mode is added to glibc's soft-fp
(although it could be if someone wanted to emulate such processor
support).
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.
* soft-fp/soft-fp.h (FP_DENORM_ZERO): New macro.
* soft-fp/op-common.h (_FP_UNPACK_CANONICAL): Check
FP_DENORM_ZERO.
(_FP_CHECK_FLUSH_ZERO): New macro.
(_FP_ADD_INTERNAL): Call _FP_CHECK_FLUSH_ZERO.
(_FP_CMP): Likewise.
(_FP_CMP_EQ): Likewise.
(_FP_TO_INT): Do not set inexact for subnormal arguments if
FP_DENORM_ZERO.
(FP_EXTEND): Call _FP_CHECK_FLUSH_ZERO.
(FP_TRUNC): Likewise.
This patch fixes a latent bug in _FP_TO_INT regarding handling of
arguments with maximum exponent (infinities and NaNs). If the maximum
exponent is below that calculated as an overflow threshold, such
values would incorrectly be treated as normal values for the purposes
of the conversion. This could not occur for any of the conversions
actually occurring in glibc, libgcc or the Linux kernel (the maximum
exponent for float is, just, big enough to ensure overflow for
unsigned __int128), but would apply if soft-fp were used for IEEE
binary16. Appropriate checks are inserted to ensure that the maximum
exponent is always treated as an overflowing exponent, and never as a
normal one.
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.
* soft-fp/op-common.h (_FP_TO_INT): Ensure maximum exponent is
treated as invalid conversion, not as normal exponent.
This patch refactors how soft-fp comparisons handle setting exceptions
for NaN operands, so that exceptions are set through the FP_CMP macros
rather than directly in the C files calling them.
The _FP_CMP* and FP_CMP* macros gain an extra argument to specify when
exceptions should be set, 0 for no exception setting (I'm not sure
this is actually needed - at least it's not needed for IEEE operations
in glibc / libgcc, but might be relevant in some cases for kernel
use), 1 for exceptions only for signaling NaNs and 2 for exceptions
for all NaNs. This argument is handled through _FP_CMP_CHECK_NAN,
newly called by the _FP_CMP* macros when a NaN is encountered. Calls
to these macros are updated, which eliminates all the existing
checking and exception setting in soft-fp *.c files in glibc.
Tested for powerpc-nofpu. (The __unord* functions have no code
changes; the __eq* / __ge* / __le* functions get slightly larger, but
I don't think that's significant.)
* soft-fp/op-common.h (_FP_CMP_CHECK_NAN): New macro.
(_FP_CMP): Add extra argument EX. Call _FP_CMP_CHECK_NAN.
(_FP_CMP_EQ): Likewise.
(_FP_CMP_UNORD): Likewise.
* soft-fp/double.h (FP_CMP_D): Add extra argument EX.
(FP_CMP_EQ_D): Likewise.
(FP_CMP_UNORD_D): Likewise.
* soft-fp/extended.h (FP_CMP_E): Likewise.
(FP_CMP_EQ_E): Likewise.
(FP_CMP_UNORD_E): Likewise.
* soft-fp/quad.h (FP_CMP_Q): Likewise.
(FP_CMP_EQ_Q): Likewise.
(FP_CMP_UNORD_Q): Likewise.
* soft-fp/single.h (FP_CMP_S): Likewise.
(FP_CMP_EQ_S): Likewise.
(FP_CMP_UNORD_S): Likewise.
* soft-fp/eqdf2.c (__eqdf2): Update call to FP_CMP_EQ_D.
* soft-fp/eqsf2.c (__eqsf2): Update call to FP_CMP_EQ_S.
* soft-fp/eqtf2.c (__eqtf2): Update call to FP_CMP_EQ_Q.
* soft-fp/gedf2.c (__gedf2): Update call to FP_CMP_D.
* soft-fp/gesf2.c (__gesf2): Update call to FP_CMP_S.
* soft-fp/getf2.c (__getf2): Update call to FP_CMP_Q.
* soft-fp/ledf2.c (__ledf2): Update call to FP_CMP_D.
* soft-fp/lesf2.c (__lesf2): Update call to FP_CMP_S.
* soft-fp/letf2.c (__letf2): Update call to FP_CMP_Q.
* soft-fp/unorddf2.c (__unorddf2): Update call to FP_CMP_UNORD_D.
* soft-fp/unordsf2.c (__unordsf2): Update call to FP_CMP_UNORD_S.
* soft-fp/unordtf2.c (__unordtf2): Update call to FP_CMP_UNORD_Q.
* sysdeps/alpha/soft-fp/ots_cmpe.c (internal_compare): Update call
to FP_CMP_Q.
* sysdeps/sparc/sparc32/soft-fp/q_cmp.c (_Q_cmp): Update call to
FP_CMP_Q.
* sysdeps/sparc/sparc32/soft-fp/q_cmpe.c (_Q_cmpe): Likewise.
* sysdeps/sparc/sparc32/soft-fp/q_feq.c (_Q_feq): Update call to
FP_CMP_EQ_Q.
* sysdeps/sparc/sparc32/soft-fp/q_fge.c (_Q_fge): Update call to
FP_CMP_Q.
* sysdeps/sparc/sparc32/soft-fp/q_fgt.c (_Q_fgt): Likewise.
* sysdeps/sparc/sparc32/soft-fp/q_fle.c (_Q_fle): Likewise.
* sysdeps/sparc/sparc32/soft-fp/q_flt.c (_Q_flt): Likewise.
* sysdeps/sparc/sparc32/soft-fp/q_fne.c (_Q_fne): Update call to
FP_CMP_EQ_Q.
* sysdeps/sparc/sparc64/soft-fp/qp_cmp.c (_Qp_cmp): Update call to
FP_CMP_Q.
* sysdeps/sparc/sparc64/soft-fp/qp_cmpe.c (_Qp_cmpe): Likewise.
* sysdeps/sparc/sparc64/soft-fp/qp_feq.c (_Qp_feq): Update call to
FP_CMP_EQ_Q.
* sysdeps/sparc/sparc64/soft-fp/qp_fge.c (_Qp_fge): Update call to
FP_CMP_Q.
* sysdeps/sparc/sparc64/soft-fp/qp_fgt.c (_Qp_fgt): Likewise.
* sysdeps/sparc/sparc64/soft-fp/qp_fle.c (_Qp_fle): Likewise.
* sysdeps/sparc/sparc64/soft-fp/qp_flt.c (_Qp_flt): Likewise.
* sysdeps/sparc/sparc64/soft-fp/qp_fne.c (_Qp_fne): Update call to
FP_CMP_EQ_Q.
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.
As noted in
<https://sourceware.org/ml/libc-alpha/2013-10/msg00516.html>, the
soft-fp macro FP_CLEAR_EXCEPTIONS should not be necessary, as soft-fp
code should never set an exception and later clear it.
In fact, all four uses in glibc (for SPARC) are indeed unnecessary:
they appear in files that convert 32-bit or 64-bit integers to IEEE
binary128, an operation that can never raise any exceptions. If this
was intended to enable the compiler to optimize away any FP_FROM_INT
code testing for exceptional cases, we now have a better way of doing
this: defining FP_NO_EXCEPTIONS before including soft-fp.h causes all
code handling exceptions to be stubbed out, and the rounding mode to
be hardwired for round-to-zero, to allow such optimizations for source
files where (a) the operation in question, for the particular types in
question, can never raise exceptions, but (b) some instances of the
operation for other types can, so the macros used in the file do
contain references to rounding or exceptions, albeit dead in that
particular file.
The uses in the Linux kernel are also unnecessary (clearing exceptions
at a point where they are already cleared).
This patch duly removes FP_CLEAR_EXCEPTIONS, making the SPARC code in
question use FP_NO_EXCEPTIONS and stop using exception-related macros.
* soft-fp/soft-fp.h (FP_CLEAR_EXCEPTIONS): Remove macro.
* sysdeps/sparc/sparc32/soft-fp/q_itoq.c: Define FP_NO_EXCEPTIONS.
(_Q_itoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or
FP_HANDLE_EXCEPTIONS.
* sysdeps/sparc/sparc32/soft-fp/q_lltoq.c: Define FP_NO_EXCEPTIONS.
(_Q_lltoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or
FP_HANDLE_EXCEPTIONS.
* sysdeps/sparc/sparc32/soft-fp/q_ulltoq.c: Define FP_NO_EXCEPTIONS.
(_Q_ulltoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or
FP_HANDLE_EXCEPTIONS.
* sysdeps/sparc/sparc32/soft-fp/q_utoq.c: Define FP_NO_EXCEPTIONS.
(_Q_utoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or
FP_HANDLE_EXCEPTIONS.
This patch fixes formatting of comments in soft-fp (in particular, the
normal style in glibc does not have a leading '*' on each line, and
comments should start with capital letters and end with ". */").
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.
* soft-fp/extended.h: Fix comment formatting.
* soft-fp/op-1.h: Likewise.
* soft-fp/op-2.h: Likewise.
* soft-fp/op-4.h: Likewise.
* soft-fp/op-8.h: Likewise.
* soft-fp/op-common.h: Likewise.
* soft-fp/soft-fp.h: Likewise.
This patch corrects some soft-fp formatting that failed to follow the
GNU Coding Standards.
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch.
* soft-fp/op-common.h (_FP_TO_INT): Correct formatting.
Continuing the soft-fp variable renaming from
<https://sourceware.org/ml/libc-alpha/2014-06/msg00434.html> to avoid
shadowing if two macros happen to use the same variable name and that
variable is involved in an argument one of those macros passes to
another, this patch renames variables in op-[1248].h. (The two
patches are to different files and are independent of each other.)
Tested for powerpc32 (soft-float) and mips64 that this makes no change
to the disassembly of installed shared libraries.
* soft-fp/op-1.h (_FP_UNPACK_RAW_1): Rename local variables to
include macro name.
(_FP_UNPACK_RAW_1_P): Likewise.
(_FP_PACK_RAW_1): Likewise.
(_FP_PACK_RAW_1_P): Likewise.
(_FP_MUL_MEAT_1_wide): Likewise.
(_FP_MUL_MEAT_DW_1_hard): Likewise.
(_FP_MUL_MEAT_1_hard): Likewise.
(_FP_DIV_MEAT_1_imm): Likewise.
(_FP_DIV_MEAT_1_udiv_norm): Likewise.
(_FP_DIV_MEAT_1_udiv): Likewise.
* soft-fp/op-2.h (__FP_FRAC_DEC_2): Likewise.
(_FP_UNPACK_RAW_2): Likewise.
(_FP_UNPACK_RAW_2_P): Likewise.
(_FP_PACK_RAW_2): Likewise.
(_FP_PACK_RAW_2_P): Likewise.
(_FP_MUL_MEAT_DW_2_wide): Likewise.
(_FP_MUL_MEAT_2_wide): Likewise.
(_FP_MUL_MEAT_DW_2_wide_3mul): Likewise.
(_FP_MUL_MEAT_2_wide_3mul): Likewise.
(_FP_MUL_MEAT_DW_2_gmp): Likewise.
(_FP_MUL_MEAT_2_gmp): Likewise.
(_FP_DIV_MEAT_2_udiv): Likewise.
* soft-fp/op-4.h (_FP_FRAC_SLL_4): Likewise.
(_FP_FRAC_SRL_4): Likewise.
(_FP_FRAC_SRST_4): Likewise.
(_FP_FRAC_SRS_4): Likewise.
(_FP_UNPACK_RAW_4): Likewise.
(_FP_UNPACK_RAW_4_P): Likewise.
(_FP_PACK_RAW_4): Likewise.
(_FP_PACK_RAW_4_P): Likewise.
(_FP_MUL_MEAT_DW_4_wide): Likewise.
(_FP_MUL_MEAT_4_wide): Likewise.
(_FP_MUL_MEAT_4_gmp): Likewise.
(umul_ppppmnnn): Likewise.
(_FP_DIV_MEAT_4_udiv): Likewise.
(__FP_FRAC_ADD_4): Likewise.
(__FP_FRAC_SUB_3): Likewise.
(__FP_FRAC_SUB_4): Likewise.
(__FP_FRAC_DEC_3): Likewise.
(__FP_FRAC_DEC_4): Likewise.
(__FP_FRAC_ADDI_4): Likewise.
* soft-fp/op-8.h (_FP_FRAC_SLL_8): Likewise.
(_FP_FRAC_SRL_8): Likewise.
(_FP_FRAC_SRS_8): Likewise.
In <https://sourceware.org/ml/libc-alpha/2013-06/msg00851.html>, I
fixed a bug caused by multiple soft-fp macros using the same variable
names, resulting in shadowing when one macro called another that used
the same variable name, with an argument involving the variable in the
outer macro. The fix was to rename the local variables so their names
included the containing macro name, to ensure uniqueness.
I noted then that this would make sense more systematically for all
variables in any soft-fp macro. Since then, I've used such variable
names in new soft-fp macros. This patch now converts existing macros
in extended.h and op-common.h to use this convention. (op-[1248].h
are intended to be converted separately.)
(Name conflicts could arise for label names as well, but because those
are function-scope in C any such conflict will give an immediate
compile error rather than a subtle bug, so there's no need for
preemptive renaming in that case.)
Tested for powerpc32 (soft-float) and mips64 that this makes no change
to the disassembly of installed shared libraries.
* soft-fp/extended.h (FP_UNPACK_RAW_E): Rename local variables to
include macro name.
(FP_UNPACK_RAW_EP): Likewise.
(FP_PACK_RAW_E): Likewise.
(FP_PACK_RAW_EP): Likewise.
* soft-fp/op-common.h (_FP_UNPACK_CANONICAL): Likewise.
(_FP_ISSIGNAN): Likewise.
(_FP_ADD_INTERNAL): Likewise.
(_FP_FMA): Likewise.
(_FP_CMP): Likewise.
(_FP_SQRT): Likewise.
(_FP_TO_INT): Likewise.
(_FP_FROM_INT): Likewise.
(FP_EXTEND): Likewise.
(_FP_DIV_MEAT_N_loop): Likewise.
In <https://sourceware.org/ml/libc-alpha/2014-01/msg00196.html> I
noted it was necessary to add includes of Makeconfig early in various
subdirectory makefiles for the tests-special variable settings added
by that patch to be conditional on configuration information. No-one
commented on the general question there of whether Makeconfig should
always be included immediately after the definition of subdir.
This patch implements that early inclusion of Makeconfig in each
directory (which is a lot easier than consistent placement of includes
of Rules). Includes are added if needed, or moved up if already
present. Subdirectory "all:" targets are removed, since Makeconfig
provides one.
There is potential for further cleanups I haven't done. Rules and
Makerules have code such as
ifneq "$(findstring env,$(origin headers))" ""
headers :=
endif
to override to empty any value of various variables that came from the
environment. I think there is a case for Makeconfig setting all the
subdirectory variables (other than subdir) to empty to ensure no
outside value is going to take effect if a subdirectory fails to
define a variable. (A list of such variables, possibly out of date
and incomplete, is in manual/maint.texi.) Rules and Makerules would
give errors if Makeconfig hadn't already been included, instead of
including it themselves. The special code to override values coming
from the environment would then be obsolete and could be removed.
Tested x86_64, including that installed binaries are identical before
and after the patch.
* argp/Makefile: Include Makeconfig immediately after defining
subdir.
* assert/Makefile: Likewise.
* benchtests/Makefile: Likewise.
* catgets/Makefile: Likewise.
* conform/Makefile: Likewise.
* crypt/Makefile: Likewise.
* csu/Makefile: Likewise.
(all): Remove target.
* ctype/Makefile: Include Makeconfig immediately after defining
subdir.
* debug/Makefile: Likewise.
* dirent/Makefile: Likewise.
* dlfcn/Makefile: Likewise.
* gmon/Makefile: Likewise.
* gnulib/Makefile: Likewise.
* grp/Makefile: Likewise.
* gshadow/Makefile: Likewise.
* hesiod/Makefile: Likewise.
* hurd/Makefile: Likewise.
(all): Remove target.
* iconvdata/Makefile: Include Makeconfig immediately after
defining subdir.
* inet/Makefile: Likewise.
* intl/Makefile: Likewise.
* io/Makefile: Likewise.
* libio/Makefile: Likewise.
(all): Remove target.
* locale/Makefile: Include Makeconfig immediately after defining
subdir.
* login/Makefile: Likewise.
* mach/Makefile: Likewise.
(all): Remove target.
* malloc/Makefile: Include Makeconfig immediately after defining
subdir.
(all): Remove target.
* manual/Makefile: Include Makeconfig immediately after defining
subdir.
* math/Makefile: Likewise.
* misc/Makefile: Likewise.
* nis/Makefile: Likewise.
* nss/Makefile: Likewise.
* po/Makefile: Likewise.
(all): Remove target.
* posix/Makefile: Include Makeconfig immediately after defining
subdir.
* pwd/Makefile: Likewise.
* resolv/Makefile: Likewise.
* resource/Makefile: Likewise.
* rt/Makefile: Likewise.
* setjmp/Makefile: Likewise.
* shadow/Makefile: Likewise.
* signal/Makefile: Likewise.
* socket/Makefile: Likewise.
* soft-fp/Makefile: Likewise.
* stdio-common/Makefile: Likewise.
* stdlib/Makefile: Likewise.
* streams/Makefile: Likewise.
* string/Makefile: Likewise.
* sunrpc/Makefile: Likewise.
(all): Remove target.
* sysvipc/Makefile: Include Makeconfig immediately after defining
subdir.
* termios/Makefile: Likewise.
* time/Makefile: Likewise.
* timezone/Makefile: Likewise.
(all): Remove target.
* wcsmbs/Makefile: Include Makeconfig immediately after defining
subdir.
* wctype/Makefile: Likewise.
libidn/ChangeLog:
* Makefile: Include Makeconfig immediately after defining subdir.
localedata/ChangeLog:
* Makefile: Include Makeconfig immediately after defining subdir.
(all): Remove target.
nptl/ChangeLog:
* Makefile: Include Makeconfig immediately after defining subdir.
nptl_db/ChangeLog:
* Makefile: Include Makeconfig immediately after defining subdir.
IEEE 754-2008 defines two ways in which tiny results can be detected,
"before rounding" (based on the infinite-precision result) and "after
rounding" (based on the result when rounded to normal precision as if
the exponent range were unbounded). All binary operations on an
architecture must use the same choice of how tininess is detected.
soft-fp has so far implemented only before-rounding tininess
detection. This patch adds support for after-rounding tininess
detection. A new macro _FP_TININESS_AFTER_ROUNDING is added that
sfp-machine.h must define (soft-fp is meant to be self-contained so
the existing tininess.h files aren't used here, though the information
going in sfp-machine.h has been taken from them). The soft-fp macros
dealing with raising underflow exceptions then handle the cases where
the choice matters specially, rounding a copy of the input to the
appropriate precision to see if a value that's tiny before rounding
isn't tiny after rounding.
Tested for mips64 using GCC trunk (which now uses soft-fp on MIPS, so
supporting exceptions and rounding modes for long double where not
previously supported - this is the immediate motivation for doing this
patch now) together with (a) a patch to sysdeps/mips/math-tests.h to
enable exceptions / rounding modes tests for long double for GCC 4.9
and later, and (b) corresponding changes applied to libgcc's soft-fp
and sfp-machine.h files. In the libgcc context this is also tested on
x86_64 (also an after-rounding architecture) with testcases for
__float128 that I intend to add to the GCC testsuite when updating
soft-fp there.
(To be clear: this patch does not fix any glibc bugs that were
user-visible in past releases, since after-rounding architectures
didn't use soft-fp in any affected case with support for
floating-point exceptions - so there is no corresponding Bugzilla bug.
Rather, it works together with the GCC changes to use soft-fp on MIPS
to allow previously absent long double functionality to work properly,
and allows soft-fp to be used in glibc on after-rounding architectures
in cases where it couldn't previously be used.)
* soft-fp/op-common.h (_FP_DECL): Mark exponent as possibly
unused.
(_FP_PACK_SEMIRAW): Determine tininess based on rounding shifted
value if _FP_TININESS_AFTER_ROUNDING and unrounded value is in
subnormal range.
(_FP_PACK_CANONICAL): Determine tininess based on rounding to
normal precision if _FP_TININESS_AFTER_ROUNDING and unrounded
value has largest subnormal exponent.
* soft-fp/soft-fp.h [FP_NO_EXCEPTIONS]
(_FP_TININESS_AFTER_ROUNDING): Undefine and redefine to 0.
* sysdeps/aarch64/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): New macro.
* sysdeps/alpha/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/arm/soft-fp/sfp-machine.h (_FP_TININESS_AFTER_ROUNDING):
Likewise.
* sysdeps/mips/mips64/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/mips/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/powerpc/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/sh/soft-fp/sfp-machine.h (_FP_TININESS_AFTER_ROUNDING):
Likewise.
* sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
(_FP_TININESS_AFTER_ROUNDING): Likewise.
* sysdeps/tile/sfp-machine.h (_FP_TININESS_AFTER_ROUNDING):
Likewise.
[BZ #15442] This adds support for the inverse interpretation of the
quiet bit of IEEE 754 floating-point NaN data that some processors
use. This includes in particular MIPS architecture processors; the
payload used for the canonical qNaN encoding is updated accordingly
so as not to interfere with the quiet bit.
Seen in, e.g. ports/sysdeps/alpha/soft-fp/ots_mul.c.
The problem here is we have a switch on the class of X*Y, followed by
a switch on the class of R. The exponent field of R really is not set
by the first switch for NaN outputs, because we know it's not going to
be used. The compiler is not smart enough to see through this.
By pulling the exponent computation out of the NORMAL*NORMAL path, we
will not be pessimizing the most common case, while still providing an
arbitrary value to satisfy the compiler.
* soft-fp/soft-fp.h (FP_CUR_EXCEPTIONS): Define.
(FP_TRAPPING_EXCEPTIONS): Provide default implementation.
* sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
(FP_TRAPPING_EXCEPTIONS): Define.
* sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
(FP_TRAPPING_EXCEPTIONS): Define.
* soft-fp/op-common.h (_FP_PACK_SEMIRAW): Signal underflow for
subnormals only when inexact has been signalled or underflow
exceptions are enabled.
(_FP_PACK_CANONICAL): Likewise.
FP_UNPACK_SEMIRAW_DP): Use _FP_UNPACK_RAW_1 instead of
_FP_UNPACK_RAW_2, fix up first argument.
2008-12-01 Fredrik Unger <fred@tree.se>
* soft-fp/double.h [_FP_W_TYPE_SIZE >= 64] (FP_UNPACK_SEMIRAW_D,
FP_UNPACK_SEMIRAW_DP): Use _FP_UNPACK_RAW_1 instead of
_FP_UNPACK_RAW_2, fix up first argument.
with setting the sticky bit.
* math/test-misc.c (main): Add more truncation tests.
* soft-fp/floatunsidf.c (__floatunsidf): Use DFtype instead of
double in the function declaration.
* soft-fp/floatundidf.c (__floatundidf): Use DFtype instead of
double in the function declaration.
* soft-fp/floatunsisf.c (__floatunsisf): Use SFtype instead of
float in the function declaration.
* soft-fp/floatunsisf.c (__floatunsisf): Use SFtype instead of
float in the function declaration.
* soft-fp/extended.h (FP_UNPACK_RAW_E): Do not increase X##_e for
denormal operands. Do not generate FP_EX_DENORM exception.
(FP_UNPACK_RAW_EP): Ditto.
(FP_UNPACK_SEMIRAW_E): Use FP_UNPACK_RAW_E instead of
undefined _FP_UNPACK_RAW_E.
(FP_UNPACK_SEMIRAW_EP): Use FP_UNPACK_RAW_EP instead of
undefined _FP_UNPACK_RAW_EP.
(FP_PACK_SEMIRAW_E): Use FP_PACK_RAW_E instead of
undefined _FP_PACK_RAW_E.
(FP_PACK_SEMIRAW_EP): Use FP_PACK_RAW_EP instead of
undefined _FP_PACK_RAW_EP.
* op-2.h (_FP_FRAC_COPY_2_2): Define as alias to _FP_FRAC_COPY_2.
* op-4.h (_FP_FRAC_COPY_2_2): Define as alias to _FP_FRAC_COPY_4.
* soft-fp/op-common.h (FP_EXTEND): Do not abort when
_FP_EXPBIAS_##dfs == _FP_EXPBIAS_##sfs. Handle denormals for
this case.
* soft-fp/op-common.h (FP_TRUNC): Ditto.
* soft-fp/op-common.h (FP_TRUNC): Replace raising of FP_EX_INEXACT
with setting the sticky bit.
* math/test-misc.c (main): Add more truncation tests.
2007-04-14 Uros Bizjak <ubizjak@gmail.com>
* soft-fp/floatunsidf.c (__floatunsidf): Use DFtype instead of
double in the function declaration.
* soft-fp/floatundidf.c (__floatundidf): Use DFtype instead of
double in the function declaration.
* soft-fp/floatunsisf.c (__floatunsisf): Use SFtype instead of
float in the function declaration.
* soft-fp/floatunsisf.c (__floatunsisf): Use SFtype instead of
float in the function declaration.
* soft-fp/extended.h (FP_UNPACK_RAW_E): Do not increase X##_e for
denormal operands. Do not generate FP_EX_DENORM exception.
(FP_UNPACK_RAW_EP): Ditto.
(FP_UNPACK_SEMIRAW_E): Use FP_UNPACK_RAW_E instead of
undefined _FP_UNPACK_RAW_E.
(FP_UNPACK_SEMIRAW_EP): Use FP_UNPACK_RAW_EP instead of
undefined _FP_UNPACK_RAW_EP.
(FP_PACK_SEMIRAW_E): Use FP_PACK_RAW_E instead of
undefined _FP_PACK_RAW_E.
(FP_PACK_SEMIRAW_EP): Use FP_PACK_RAW_EP instead of
undefined _FP_PACK_RAW_EP.
* op-2.h (_FP_FRAC_COPY_2_2): Define as alias to _FP_FRAC_COPY_2.
* op-4.h (_FP_FRAC_COPY_2_2): Define as alias to _FP_FRAC_COPY_4.
2007-04-16 Uros Bizjak <ubizjak@gmail.com>
Jakub Jelinek <jakub@redhat.com>
* soft-fp/op-common.h (FP_EXTEND): Do not abort when
_FP_EXPBIAS_##dfs == _FP_EXPBIAS_##sfs. Handle denormals for
this case.
* soft-fp/op-common.h (FP_TRUNC): Ditto.
2007-05-03 Jakub Jelinek <jakub@redhat.com>
