Add fromfp functions.

TS 18661-1 defines fromfp functions (fromfp, fromfpx, ufromfp,
ufromfpx, and float and long double variants) to convert from
floating-point to an integer type with any signedness and any given
width up to that of intmax_t, in any of the five IEEE rounding modes
(the usual four for binary floating point, plus rounding to nearest
with ties rounding away from zero), with control of whether in-range
non-integer values should result in the "inexact" exception being
raised.  This patch implements these functions for glibc.

These implementations are (apart from raising exceptions) pure integer
implementations; it's entirely possible optimized versions could be
devised for some architectures.  A common math/fromfp.h header
provides various common helper code that can readily be shared between
the implementations for different types.  For each type, the bulk of
the implementation is also shared between the four functions, with
wrappers that define UNSIGNED and INEXACT macros appropriately before
including the main implementation.

As the functions return intmax_t and uintmax_t without math.h being
allowed to expose those typedef names, they are declared using
__intmax_t and __uintmax_t as obtained from <bits/types.h>.

The FP_INT_* rounding direction macros are defined as ascending
integers in the order the names are listed in the TS; I see no
significant value in allowing architectures to vary the values of
them.

The libm-test machinery is duly adapted to handle unsigned int
arguments, and intmax_t and uintmax_t results.  Because each test
input is generally tested for four functions, five rounding modes and
several different widths, the libm-test.inc additions are very large.
Thus, the diffs in the body of this message exclude the libm-test.inc
changes, with the full patch being attached gzipped.  The bulk of the
new tests were generated (expanded from a test input plus rounding
results and information about where it lies in the relevant interval
between integers, to libm-test tests for all relevant combinations of
function, rounding direction and width) by a script that's included in
the patch as math/gen-fromfp-tests.py (input data
math/gen-fromfp-tests-inputs); as an ad hoc script that's not really
expected to be rerun, it's not very polished, but it's at least
plausibly useful for adding any further tests for these functions in
future.  I may split the libm-test tests up by function in future (so
both libm-test.inc and auto-libm-test-out are split into separate
files, and the tests for each function are also built and run
separately), but not for 2.25.

For no obvious reason, adding tgmath tests for the new functions
resulted in -Wuninitialized errors from test-tgmath.c about the
variable i being used uninitialized.  Those errors were correct - the
variable is read by the frexp version in test-tgmath.c (where real
frexp would write through that pointer instead of reading it) - but I
don't know why this patch would result in the pre-existing issue being
newly detected.  The patch initializes the variable to avoid those
errors.

With these changes, glibc 2.25 should have all the library features
from TS 18661-1 other than the functions that round result to narrower
type (and constant rounding directions, but I'm considering those
mainly a compiler feature not a library one).

Tested for x86_64, x86, mips64 and powerpc.

	* math/bits/mathcalls.h [__GLIBC_USE (IEC_60559_BFP_EXT)]
	(fromfp): New declaration.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (fromfpx): Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (ufromfp): Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (ufromfpx): Likewise.
	* math/tgmath.h (__TGMATH_TERNARY_FIRST_REAL_RET_ONLY): New macro.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (fromfp): Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (ufromfp): Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (fromfpx): Likewise.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (ufromfpx): Likewise.
	* math/math.h: Include <bits/types.h>.
	[__GLIBC_USE (IEC_60559_BFP_EXT)] (FP_INT_UPWARD): New enum
	constant and macro.
	(FP_INT_DOWNWARD): Likewise.
	(FP_INT_TOWARDZERO): Likewise.
	(FP_INT_TONEARESTFROMZERO): Likewise.
	(FP_INT_TONEAREST): Likewise.
	* math/Versions (fromfp): New libm symbol at version GLIBC_2.25.
	(fromfpf): Likewise.
	(fromfpl): Likewise.
	(ufromfp): Likewise.
	(ufromfpf): Likewise.
	(ufromfpl): Likewise.
	(fromfpx): Likewise.
	(fromfpxf): Likewise.
	(fromfpxl): Likewise.
	(ufromfpx): Likewise.
	(ufromfpxf): Likewise.
	(ufromfpxl): Likewise.
	* math/Makefile (libm-calls): Add s_fromfpF, s_ufromfpF,
	s_fromfpxF and s_ufromfpxF.
	* math/gen-fromfp-tests.py: New file.
	* math/gen-fromfp-tests-inputs: Likewise.
	* math/libm-test.inc: Include <stdint.h>
	(check_intmax_t): New function.
	(check_uintmax_t): Likewise.
	(struct test_fiu_M_data): New type.
	(struct test_fiu_U_data): Likewise.
	(RUN_TEST_fiu_M): New macro.
	(RUN_TEST_LOOP_fiu_M): Likewise.
	(RUN_TEST_fiu_U): Likewise.
	(RUN_TEST_LOOP_fiu_U): Likewise.
	(fromfp_test_data): New array.
	(fromfp_test): New function.
	(fromfpx_test_data): New array.
	(fromfpx_test): New function.
	(ufromfp_test_data): New array.
	(ufromfp_test): New function.
	(ufromfpx_test_data): New array.
	(ufromfpx_test): New function.
	(main): Call fromfp_test, fromfpx_test, ufromfp_test and
	ufromfpx_test.
	* math/gen-libm-test.pl (parse_args): Handle u, M and U descriptor
	characters.
	* math/test-tgmath-ret.c: Include <stdint.h>.
	(rm): New variable.
	(width): Likewise.
	(CHECK_RET_CONST_TYPE): Take extra arguments and pass them to
	called function.
	(CHECK_RET_CONST_FLOAT): Take extra arguments and pass them to
	CHECK_RET_CONST_TYPE.
	(CHECK_RET_CONST_DOUBLE): Likewise.
	(CHECK_RET_CONST_LDOUBLE): Likewise.
	(CHECK_RET_CONST): Take extra arguments and pass them to calls
	macros.
	(fromfp): New CHECK_RET_CONST call.
	(ufromfp): Likewise.
	(fromfpx): Likewise.
	(ufromfpx): Likewise.
	(do_test): Call check_return_fromfp, check_return_ufromfp,
	check_return_fromfpx and check_return_ufromfpx.
	* math/test-tgmath.c: Include <stdint.h>
	(NCALLS): Increase to 138.
	(F(compile_test)): Initialize i.  Call fromfp functions.
	(F(fromfp)): New function.
	(F(fromfpx)): Likewise.
	(F(ufromfp)): Likewise.
	(F(ufromfpx)): Likewise.
	* manual/arith.texi (Rounding Functions): Document FP_INT_UPWARD,
	FP_INT_DOWNWARD, FP_INT_TOWARDZERO, FP_INT_TONEARESTFROMZERO,
	FP_INT_TONEAREST, fromfp, fromfpf, fromfpl, ufromfp, ufromfpf,
	ufromfpl, fromfpx, fromfpxf, fromfpxl, ufromfpx, ufromfpxf and
	ufromfpxl.
	* manual/libm-err-tab.pl (@all_functions): Add fromfp, fromfpx,
	ufromfp and ufromfpx.
	* math/fromfp.h: New file.
	* sysdeps/ieee754/dbl-64/s_fromfp.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_fromfp_main.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_fromfpx.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_ufromfp.c: Likewise.
	* sysdeps/ieee754/dbl-64/s_ufromfpx.c: Likewise.
	* sysdeps/ieee754/flt-32/s_fromfpf.c: Likewise.
	* sysdeps/ieee754/flt-32/s_fromfpf_main.c: Likewise.
	* sysdeps/ieee754/flt-32/s_fromfpxf.c: Likewise.
	* sysdeps/ieee754/flt-32/s_ufromfpf.c: Likewise.
	* sysdeps/ieee754/flt-32/s_ufromfpxf.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_fromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_fromfpl_main.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_fromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_ufromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-128/s_ufromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_fromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_fromfpl_main.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_fromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_ufromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_ufromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_fromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_fromfpl_main.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_fromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_ufromfpl.c: Likewise.
	* sysdeps/ieee754/ldbl-96/s_ufromfpxl.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/Makefile (libnldbl-calls): Add fromfp,
	ufromfp, fromfpx and ufromfpx.
	(CFLAGS-nldbl-fromfp.c): New variable.
	(CFLAGS-nldbl-fromfpx.c): Likewise.
	(CFLAGS-nldbl-ufromfp.c): Likewise.
	(CFLAGS-nldbl-ufromfpx.c): Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-compat.h: Include <stdint.h>.
	* sysdeps/ieee754/ldbl-opt/nldbl-fromfp.c: New file.
	* sysdeps/ieee754/ldbl-opt/nldbl-fromfpx.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-ufromfp.c: Likewise.
	* sysdeps/ieee754/ldbl-opt/nldbl-ufromfpx.c: Likewise.
	* 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.

1 files changed, 174 insertions, 0 deletions

diff --git a/math/fromfp.h b/math/fromfp.h
new file mode 100644
index 0000000000..5d681238b1
--- /dev/null
+++ b/math/fromfp.h
@@ -0,0 +1,174 @@
+/* Round to integer type.  Common helper functions.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fenv.h>
+#include <float.h>
+#include <math.h>
+#include <math_private.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+/* The including file should have defined UNSIGNED to 0 (signed return
+   type) or 1 (unsigned return type), INEXACT to 0 (no inexact
+   exceptions) or 1 (raise inexact exceptions) and RET_TYPE to the
+   return type (intmax_t or uintmax_t).  */
+
+/* Return the maximum unbiased exponent for an argument (negative if
+   NEGATIVE is set) that might be in range for a call to a fromfp
+   function with width WIDTH (greater than 0, and not exceeding that
+   of intmax_t).  The truncated argument may still be out of range in
+   the case of negative arguments, and if not out of range it may
+   become out of range as a result of rounding.  */
+
+static int
+fromfp_max_exponent (bool negative, int width)
+{
+  if (UNSIGNED)
+    return negative ? -1 : width - 1;
+  else
+    return negative ? width - 1 : width - 2;
+}
+
+/* Return the result of rounding an integer value X (passed as the
+   absolute value; NEGATIVE is true if the value is negative), where
+   HALF_BIT is true if the bit with value 0.5 is set and MORE_BITS is
+   true if any lower bits are set, in the rounding direction
+   ROUND.  */
+
+static uintmax_t
+fromfp_round (bool negative, uintmax_t x, bool half_bit, bool more_bits,
+	      int round)
+{
+  switch (round)
+    {
+    case FP_INT_UPWARD:
+      return x + (!negative && (half_bit || more_bits));
+
+    case FP_INT_DOWNWARD:
+      return x + (negative && (half_bit || more_bits));
+
+    case FP_INT_TOWARDZERO:
+    default:
+      /* Unknown rounding directions are defined to mean unspecified
+	 rounding; treat this as truncation.  */
+      return x;
+
+    case FP_INT_TONEARESTFROMZERO:
+      return x + half_bit;
+
+    case FP_INT_TONEAREST:
+      return x + (half_bit && ((x & 1) || more_bits));
+    }
+}
+
+/* Integer rounding, of a value whose exponent EXPONENT did not exceed
+   the maximum exponent MAX_EXPONENT and so did not necessarily
+   overflow, has produced X (possibly wrapping to 0); the sign is
+   negative if NEGATIVE is true.  Return whether this overflowed the
+   allowed width.  */
+
+static bool
+fromfp_overflowed (bool negative, uintmax_t x, int exponent, int max_exponent)
+{
+  if (UNSIGNED)
+    {
+      if (negative)
+	return x != 0;
+      else if (max_exponent == INTMAX_WIDTH - 1)
+	return exponent == INTMAX_WIDTH - 1 && x == 0;
+      else
+	return x == (1ULL << (max_exponent + 1));
+    }
+  else
+    {
+      if (negative)
+	return exponent == max_exponent && x != (1ULL << max_exponent);
+      else
+	return x == (1ULL << (max_exponent + 1));
+    }
+}
+
+/* Handle a domain error for a call to a fromfp function with an
+   argument which is negative if NEGATIVE is set, and specified width
+   (not exceeding that of intmax_t) WIDTH.  The return value is
+   unspecified (with it being unclear if the result needs to fit
+   within WIDTH bits in this case); we choose to saturate to the given
+   number of bits (treating NaNs like any other value).  */
+
+static RET_TYPE
+fromfp_domain_error (bool negative, unsigned int width)
+{
+  feraiseexcept (FE_INVALID);
+  __set_errno (EDOM);
+  /* The return value is unspecified; we choose to saturate to the
+     given number of bits (treating NaNs like any other value).  */
+  if (UNSIGNED)
+    {
+      if (negative)
+	return 0;
+      else if (width == INTMAX_WIDTH)
+	return -1;
+      else
+	return (1ULL << width) - 1;
+    }
+  else
+    {
+      if (width == 0)
+	return 0;
+      else if (negative)
+	return -(1ULL << (width - 1));
+      else
+	return (1ULL << (width - 1)) - 1;
+    }
+}
+
+/* Given X, the absolute value of a floating-point number (negative if
+   NEGATIVE is set) truncated towards zero, where HALF_BIT is true if
+   the bit with value 0.5 is set and MORE_BITS is true if any lower
+   bits are set, round it in the rounding direction ROUND, handle
+   errors and exceptions and return the appropriate return value for a
+   fromfp function.  X originally had floating-point exponent
+   EXPONENT, which does not exceed MAX_EXPONENT, the return value from
+   fromfp_max_exponent with width WIDTH.  */
+
+static RET_TYPE
+fromfp_round_and_return (bool negative, uintmax_t x, bool half_bit,
+			 bool more_bits, int round, int exponent,
+			 int max_exponent, unsigned int width)
+{
+  uintmax_t uret = fromfp_round (negative, x, half_bit, more_bits, round);
+  if (fromfp_overflowed (negative, uret, exponent, max_exponent))
+    return fromfp_domain_error (negative, width);
+
+  if (INEXACT && (half_bit || more_bits))
+    {
+      /* There is no need for this to use the specific floating-point
+	 type for which this header is included, and there is no need
+	 for this header to know that type at all, so just use float
+	 here.  */
+      float force_inexact = 1.0f + FLT_MIN;
+      math_force_eval (force_inexact);
+    }
+  if (UNSIGNED)
+    /* A negative argument not rounding to zero will already have
+       produced a domain error.  */
+    return uret;
+  else
+    return negative ? -uret : uret;
+}