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eb9066203f
This patch is using the corresponding GCC builtin for roundevenf, roundeven and roundevenl if the USE_FUNCTION_BUILTIN macros are defined to one in math-use-builtins.h. These builtin functions is supported since GCC 10. The code of the generic implementation is not changed. Signed-off-by: Shen-Ta Hsieh <ibmibmibm.tw@gmail.com> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
79 lines
2.4 KiB
C
79 lines
2.4 KiB
C
/* Round to nearest integer value, rounding halfway cases to even.
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flt-32 version.
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Copyright (C) 2016-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define NO_MATH_REDIRECT
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#include <math.h>
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#include <math_private.h>
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#include <libm-alias-float.h>
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#include <math-use-builtins.h>
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#include <stdint.h>
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#define BIAS 0x7f
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#define MANT_DIG 24
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#define MAX_EXP (2 * BIAS + 1)
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float
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__roundevenf (float x)
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{
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#if USE_ROUNDEVENF_BUILTIN
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return __builtin_roundevenf (x);
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#else
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uint32_t ix, ux;
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GET_FLOAT_WORD (ix, x);
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ux = ix & 0x7fffffff;
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int exponent = ux >> (MANT_DIG - 1);
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if (exponent >= BIAS + MANT_DIG - 1)
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{
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/* Integer, infinity or NaN. */
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if (exponent == MAX_EXP)
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/* Infinity or NaN; quiet signaling NaNs. */
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return x + x;
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else
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return x;
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}
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else if (exponent >= BIAS)
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{
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/* At least 1; not necessarily an integer. Locate the bits with
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exponents 0 and -1 (when the unbiased exponent is 0, the bit
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with exponent 0 is implicit, but as the bias is odd it is OK
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to take it from the low bit of the exponent). */
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int int_pos = (BIAS + MANT_DIG - 1) - exponent;
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int half_pos = int_pos - 1;
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uint32_t half_bit = 1U << half_pos;
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uint32_t int_bit = 1U << int_pos;
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if ((ix & (int_bit | (half_bit - 1))) != 0)
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/* Carry into the exponent works correctly. No need to test
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whether HALF_BIT is set. */
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ix += half_bit;
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ix &= ~(int_bit - 1);
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}
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else if (exponent == BIAS - 1 && ux > 0x3f000000)
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/* Interval (0.5, 1). */
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ix = (ix & 0x80000000) | 0x3f800000;
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else
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/* Rounds to 0. */
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ix &= 0x80000000;
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SET_FLOAT_WORD (x, ix);
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return x;
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#endif /* ! USE_ROUNDEVENF_BUILTIN */
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}
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#ifndef __roundevenf
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libm_alias_float (__roundeven, roundeven)
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#endif
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