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119 lines
3.9 KiB
C
119 lines
3.9 KiB
C
/* Pythagorean addition using floats
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Copyright (C) 2011 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Adhemerval Zanella <azanella@br.ibm.com>, 2011
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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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <math_private.h>
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static const float two30 = 1.0737418e09;
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static const float two50 = 1.1259000e15;
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static const float two60 = 1.1529221e18;
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static const float two126 = 8.5070592e+37;
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static const float twoM50 = 8.8817842e-16;
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static const float twoM60 = 6.7762644e-21;
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static const float pdnum = 1.1754939e-38;
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/* __ieee754_hypotf(x,y)
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*
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* This a FP only version without any FP->INT conversion.
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* It is similar to default C version, making appropriates
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* overflow and underflows checks as well scaling when it
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* is needed.
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*/
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#ifdef _ARCH_PWR7
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/* POWER7 isinf and isnan optimizations are fast. */
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# define TEST_INF_NAN(x, y) \
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if (isinff(x) || isinff(y)) \
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return INFINITY; \
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if (isnanf(x) || isnanf(y)) \
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return NAN;
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# else
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/* For POWER6 and below isinf/isnan triggers LHS and PLT calls are
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* costly (especially for POWER6). */
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# define GET_TWO_FLOAT_WORD(f1,f2,i1,i2) \
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do { \
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ieee_float_shape_type gf_u1; \
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ieee_float_shape_type gf_u2; \
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gf_u1.value = (f1); \
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gf_u2.value = (f2); \
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(i1) = gf_u1.word; \
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(i2) = gf_u2.word; \
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} while (0)
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# define TEST_INF_NAN(x, y) \
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do { \
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int32_t hx, hy; \
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GET_TWO_FLOAT_WORD(x, y, hx, hy); \
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if (hy > hx) { \
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uint32_t ht = hx; hx = hy; hy = ht; \
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} \
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if (hx >= 0x7f800000) { \
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if (hx == 0x7f800000 || hy == 0x7f800000) \
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return INFINITY; \
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return NAN; \
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} \
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} while (0)
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#endif
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float
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__ieee754_hypotf (float x, float y)
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{
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x = fabsf (x);
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y = fabsf (y);
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TEST_INF_NAN (x, y);
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if (y > x)
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{
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float t = y;
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y = x;
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x = t;
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}
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if (y == 0.0 || (x / y) > two30)
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{
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return x + y;
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}
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if (x > two50)
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{
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x *= twoM60;
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y *= twoM60;
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return __ieee754_sqrtf (x * x + y * y) / twoM60;
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}
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if (y < twoM50)
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{
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if (y <= pdnum)
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{
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x *= two126;
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y *= two126;
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return __ieee754_sqrtf (x * x + y * y) / two126;
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}
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else
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{
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x *= two60;
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y *= two60;
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return __ieee754_sqrtf (x * x + y * y) / two60;
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}
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}
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return __ieee754_sqrtf (x * x + y * y);
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}
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strong_alias (__ieee754_hypotf, __hypotf_finite)
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