2 Commits

Author	SHA1	Message	Date
Joseph Myers	d8742dd82f	Add narrowing add functions. ... This patch adds the narrowing add functions from TS 18661-1 to glibc's libm: fadd, faddl, daddl, f32addf64, f32addf32x, f32xaddf64 for all configurations; f32addf64x, f32addf128, f64addf64x, f64addf128, f32xaddf64x, f32xaddf128, f64xaddf128 for configurations with _Float64x and _Float128; __nldbl_daddl for ldbl-opt. As discussed for the build infrastructure patch, tgmath.h support is deliberately deferred, and FP_FAST_* macros are not applicable without optimized function implementations. Function implementations are added for all relevant pairs of formats (including certain cases of a format and itself where more than one type has that format). The main implementations use round-to-odd, or a trivial computation in the case where both formats are the same or where the wider format is IBM long double (in which case we don't attempt to be correctly rounding). The sysdeps/ieee754/soft-fp implementations use soft-fp, and are used automatically for configurations without exceptions and rounding modes by virtue of existing Implies files. As previously discussed, optimized versions for particular architectures are possible, but not included. i386 gets a special version of f32xaddf64 to avoid problems with double rounding (similar to the existing fdim version), since this function must round just once without an intermediate rounding to long double. (No such special version is needed for any other function, because the nontrivial functions use round-to-odd, which does the intermediate computation with the rounding mode set to round-to-zero, and double rounding is OK except in round-to-nearest mode, so is OK for that intermediate round-to-zero computation.) mul and div will need slightly different special versions for i386 (using round-to-odd on long double instead of precision control) because of the possibility of inexact intermediate results in the subnormal range for double. To reduce duplication among the different function implementations, math-narrow.h gets macros CHECK_NARROW_ADD, NARROW_ADD_ROUND_TO_ODD and NARROW_ADD_TRIVIAL. In the trivial cases and for any architecture-specific optimized implementations, the overhead of the errno setting might be significant, but I think that's best handled through compiler built-in functions rather than providing separate no-errno versions in glibc (and likewise there are no __*_finite entry points for these function provided, __*_finite effectively being no-errno versions at present in most cases). Tested for x86_64 and x86, with both GCC 6 and GCC 7. Tested for mips64 (all three ABIs, both hard and soft float) and powerpc with GCC 7. Tested with build-many-glibcs.py with both GCC 6 and GCC 7. * math/Makefile (libm-narrow-fns): Add add. (libm-test-funcs-narrow): Likewise. * math/Versions (GLIBC_2.28): Add narrowing add functions. * math/bits/mathcalls-narrow.h (add): Use __MATHCALL_NARROW . * math/gen-auto-libm-tests.c (test_functions): Add add. * math/math-narrow.h (CHECK_NARROW_ADD): New macro. (NARROW_ADD_ROUND_TO_ODD): Likewise. (NARROW_ADD_TRIVIAL): Likewise. * sysdeps/ieee754/float128/float128_private.h (__faddl): New macro. (__daddl): Likewise. * sysdeps/ieee754/ldbl-opt/Makefile (libnldbl-calls): Add fadd and dadd. (CFLAGS-nldbl-dadd.c): New variable. (CFLAGS-nldbl-fadd.c): Likewise. * sysdeps/ieee754/ldbl-opt/Versions (GLIBC_2.28): Add __nldbl_daddl. * sysdeps/ieee754/ldbl-opt/nldbl-compat.h (__nldbl_daddl): New prototype. * manual/arith.texi (Misc FP Arithmetic): Document fadd, faddl, daddl, fMaddfN, fMaddfNx, fMxaddfN and fMxaddfNx. * math/auto-libm-test-in: Add tests of add. * math/auto-libm-test-out-narrow-add: New generated file. * math/libm-test-narrow-add.inc: New file. * sysdeps/i386/fpu/s_f32xaddf64.c: Likewise. * sysdeps/ieee754/dbl-64/s_f32xaddf64.c: Likewise. * sysdeps/ieee754/dbl-64/s_fadd.c: Likewise. * sysdeps/ieee754/float128/s_f32addf128.c: Likewise. * sysdeps/ieee754/float128/s_f64addf128.c: Likewise. * sysdeps/ieee754/float128/s_f64xaddf128.c: Likewise. * sysdeps/ieee754/ldbl-128/s_daddl.c: Likewise. * sysdeps/ieee754/ldbl-128/s_f64xaddf128.c: Likewise. * sysdeps/ieee754/ldbl-128/s_faddl.c: Likewise. * sysdeps/ieee754/ldbl-128ibm/s_daddl.c: Likewise. * sysdeps/ieee754/ldbl-128ibm/s_faddl.c: Likewise. * sysdeps/ieee754/ldbl-96/s_daddl.c: Likewise. * sysdeps/ieee754/ldbl-96/s_faddl.c: Likewise. * sysdeps/ieee754/ldbl-opt/nldbl-dadd.c: Likewise. * sysdeps/ieee754/ldbl-opt/nldbl-fadd.c: Likewise. * sysdeps/ieee754/soft-fp/s_daddl.c: Likewise. * sysdeps/ieee754/soft-fp/s_fadd.c: Likewise. * sysdeps/ieee754/soft-fp/s_faddl.c: Likewise. * sysdeps/powerpc/fpu/libm-test-ulps: Update. * sysdeps/mach/hurd/i386/libm.abilist: Likewise. * 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/riscv/rv64/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/tilegx32/libm.abilist: Likewise. * sysdeps/unix/sysv/linux/tile/tilegx64/libm.abilist: Likewise. * sysdeps/unix/sysv/linux/x86_64/64/libm.abilist: Likewise. * sysdeps/unix/sysv/linux/x86_64/x32/libm.abilist: Likewise.	2018-02-10 02:08:43 +00:00
Joseph Myers	63716ab270	Add build infrastructure for narrowing libm functions. ... TS 18661-1 defines libm functions that carry out an operation (+ - * / sqrt fma) on their arguments and return a result rounded to a (usually) narrower type, as if the original result were computed to infinite precision and then rounded directly to the result type without any intermediate rounding to the argument type. For example, fadd, faddl and daddl for addition. These are the last remaining TS 18661-1 functions left to be added to glibc. TS 18661-3 extends this to corresponding functions for _FloatN and _FloatNx types. As functions parametrized by two rather than one varying floating-point types, these functions require infrastructure in glibc that was not required for previous libm functions. This patch provides such infrastructure - excluding test support, and actual function implementations, which will be in subsequent patches. Declaring the functions uses a header bits/mathcalls-narrow.h, which is included many times, for each relevant pair of types. This will end up containing macro calls of the form __MATHCALL_NARROW (__MATHCALL_NAME (add), __MATHCALL_REDIR_NAME (add), 2); for each family of narrowing functions. (The structure of this macro call, with the calls to __MATHCALL_NAME and __MATHCALL_REDIR_NAME there rather than in the definition of __MATHCALL_NARROW, arises from the names such as "add" *not* themselves being reserved identifiers - meaning it's necessary to avoid any indirection that would result in a user-defined "add" macro being expanded.) Whereas for existing functions declaring long double functions is disabled if _LIBC in the case where they alias double functions, to facilitate defining the long double functions as aliases of the double ones, there is no such logic for the narrowing functions in this patch. Rather, the files defining such functions are expected to use #define to hide the original declarations of the alias names, to avoid errors about defining aliases with incompatible types. math/Makefile support is added for building the functions (listed in libm-narrow-fns, currently empty) for all relevant pairs of types. An internal header math-narrow.h is added for macros shared between multiple function implementations - currently a ROUND_TO_ODD macro to facilitate writing functions using the round-to-odd implementation approach, and alias macros to create all the required function aliases. libc_feholdexcept_setroundf128 and libc_feupdateenv_testf128 are added for use when required (only for x86_64). float128_private.h support is added for ldbl-128 narrowing functions to be used for _Float128. Certain things are specifically omitted from this patch and the immediate followups. tgmath.h support is deferred; there remain unresolved questions about how the type-generic macros for these functions are supposed to work, especially in the case of arguments of integer type. The math.h / bits/mathcalls-narrow.h logic, and the logic for determining what functions / aliases to define, will need some adjustments to support the sqrt and fma functions, where e.g. f32xsqrtf64 can just be an alias for sqrt rather than a separate function. TS 18661-1 defines FP_FAST_* macros but no support is included for defining them (they won't in general be true without architecture-specific optimized function versions). For each of the function groups (add sub mul div sqrt fma) there are always six functions present (e.g. fadd, faddl, daddl, f32addf64, f32addf32x, f32xaddf64). When _Float64x and _Float128 are supported, there are seven more (e.g. f32addf64x, f32addf128, f64addf64x, f64addf128, f32xaddf64x, f32xaddf128, f64xaddf128). In addition, in the ldbl-opt case there are function names such as __nldbl_daddl (an alias for f32xaddf64, which is not a reserved name in TS 18661-1, only in TS 18661-3), for calls to daddl to be mapped to in the -mlong-double-64 case. (Calls to faddl just get mapped to fadd, and for sqrt and fma there won't be __nldbl_* functions because dsqrtl and dfmal can just be mapped to sqrt and fma with -mlong-double-64.) While there are six or thirteen functions present in each group (plus __nldbl_* names only as an ABI, not an API), not all are distinct; they fall in various groups of aliases. There are two distinct versions built if long double has the same format as double; four if they have distinct formats but there is no _Float64x or _Float128 support; five if long double has binary128 format; seven when _Float128 is distinct from long double. Architecture-specific optimized versions are possible, but not included in my patches. For example, IA64 generally supports narrowing the result of most floating-point instructions; Power ISA 2.07 (POWER8) supports double values as arguments to float instructions, with the results narrowed as expected; Power ISA 3 (POWER9) supports round-to-odd for float128 instructions, so meaning that approach can be used without needing to set and restore the rounding mode and test "inexact". I intend to leave any such optimized versions to the architecture maintainers. Generally in such cases it would also make sense for calls to these functions to be expanded inline (given -fno-math-errno); I put a suggestion for TS 18661-1 built-in functions at <https://gcc.gnu.org/wiki/SummerOfCode>. Tested for x86_64 (this patch in isolation, as well as testing for various configurations in conjunction with further patches). * math/bits/mathcalls-narrow.h: New file. * include/bits/mathcalls-narrow.h: Likewise. * math/math-narrow.h: Likewise. * math/math.h (__MATHCALL_NARROW_ARGS_1): New macro. (__MATHCALL_NARROW_ARGS_2): Likewise. (__MATHCALL_NARROW_ARGS_3): Likewise. (__MATHCALL_NARROW_NORMAL): Likewise. (__MATHCALL_NARROW_REDIR): Likewise. (__MATHCALL_NARROW): Likewise. [__GLIBC_USE (IEC_60559_BFP_EXT)]: Repeatedly include <bits/mathcalls-narrow.h> with _Mret_, _Marg_ and __MATHCALL_NAME defined. [__GLIBC_USE (IEC_60559_TYPES_EXT)]: Likewise. * math/Makefile (headers): Add bits/mathcalls-narrow.h. (libm-narrow-fns): New variable. (libm-narrow-types-basic): Likewise. (libm-narrow-types-ldouble-yes): Likewise. (libm-narrow-types-float128-yes): Likewise. (libm-narrow-types-float128-alias-yes): Likewise. (libm-narrow-types): Likewise. (libm-routines): Add narrowing functions. * sysdeps/i386/fpu/fenv_private.h [__x86_64__] (libc_feholdexcept_setroundf128): New macro. [__x86_64__] (libc_feupdateenv_testf128): Likewise. * sysdeps/ieee754/float128/float128_private.h: Include <math/math-narrow.h>. [libc_feholdexcept_setroundf128] (libc_feholdexcept_setroundl): Undefine and redefine. [libc_feupdateenv_testf128] (libc_feupdateenv_testl): Likewise. (libm_alias_float_ldouble): Undefine and redefine. (libm_alias_double_ldouble): Likewise.	2018-02-09 21:18:52 +00:00