mirror of git://sourceware.org/git/glibc.git
math: Optimize float ilogb/llogb
It removes the wrapper by moving the error/EDOM handling to an out-of-line implementation (__math_invalidf_i/__math_invalidf_li). Also, __glibc_unlikely is used on errors case since it helps code generation on recent gcc. The code now builds to with gcc-14 on aarch64: 0000000000000000 <__ilogbf>: 0: 1e260000 fmov w0, s0 4: d3577801 ubfx x1, x0, #23, #8 8: 340000e1 cbz w1, 24 <__ilogbf+0x24> c: 5101fc20 sub w0, w1, #0x7f 10: 7103fc3f cmp w1, #0xff 14: 54000040 b.eq 1c <__ilogbf+0x1c> // b.none 18: d65f03c0 ret 1c: 12b00000 mov w0, #0x7fffffff // #2147483647 20: 14000000 b 0 <__math_invalidf_i> 24: 53175800 lsl w0, w0, #9 28: 340000a0 cbz w0, 3c <__ilogbf+0x3c> 2c: 5ac01000 clz w0, w0 30: 12800fc1 mov w1, #0xffffff81 // #-127 34: 4b000020 sub w0, w1, w0 38: d65f03c0 ret 3c: 320107e0 mov w0, #0x80000001 // #-2147483647 40: 14000000 b 0 <__math_invalidf_i> Some ABI requires additional adjustments: * i386 and m68k requires to use the template version, since both provide __ieee754_ilogb implementatations. * loongarch uses a custom implementation as well. * powerpc64le also has a custom implementation for POWER9, which is also used for float and float128 version. The generic e_ilogb.c implementation is moved on powerpc to keep the current code as-is. Checked on aarch64-linux-gnu and x86_64-linux-gnu. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
This commit is contained in:
parent
afe09d44f3
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#include <math-type-macros-float.h>
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#include <w_ilogb_template.c>
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@ -0,0 +1,2 @@
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#include <math-type-macros-float.h>
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#include <w_llogb_template.c>
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@ -1,41 +1 @@
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/* Get integer exponent of a floating-point value.
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Copyright (C) 1999-2025 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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#include <limits.h>
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#include <math.h>
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#include <stdbit.h>
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#include "math_config.h"
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int
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__ieee754_ilogbf (float x)
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{
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uint32_t ux = asuint (x);
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int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
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if (ex == 0) /* zero or subnormal */
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{
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/* Clear sign and exponent. */
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ux <<= 1 + EXPONENT_WIDTH;
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if (ux == 0)
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return FP_ILOGB0;
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/* subnormal */
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return -127 - stdc_leading_zeros (ux);
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}
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if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
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return ux << (1 + EXPONENT_WIDTH) ? FP_ILOGBNAN : INT_MAX;
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return ex - 127;
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}
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/* ilogbf is implemented at w_ilogbf.c */
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@ -208,6 +208,8 @@ attribute_hidden float __math_uflowf (uint32_t);
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attribute_hidden float __math_may_uflowf (uint32_t);
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attribute_hidden float __math_divzerof (uint32_t);
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attribute_hidden float __math_invalidf (float);
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attribute_hidden int __math_invalidf_i (int);
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attribute_hidden long int __math_invalidf_li (long int);
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attribute_hidden float __math_edomf (float x);
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/* Shared between expf, exp2f, exp10f, and powf. */
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@ -16,6 +16,7 @@
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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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#include <math-barriers.h>
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#include "math_config.h"
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#if WANT_ERRNO
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@ -27,8 +28,24 @@ with_errnof (float y, int e)
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errno = e;
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return y;
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}
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NOINLINE static int
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with_errnof_i (int y, int e)
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{
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errno = e;
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return y;
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}
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NOINLINE static long int
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with_errnof_li (long int y, int e)
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{
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errno = e;
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return y;
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}
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#else
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# define with_errnof(x, e) (x)
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# define with_errnof_i(x, x) (x)
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# define with_errnof_li(x, x) (x)
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#endif
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attribute_hidden float
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@ -80,3 +97,19 @@ __math_invalidf (float x)
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float y = (x - x) / (x - x);
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return isnan (x) ? y : with_errnof (y, EDOM);
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}
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attribute_hidden int
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__math_invalidf_i (int x)
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{
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float y = 0.0f / 0.0f;
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math_force_eval (y);
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return with_errnof_i (x, EDOM);
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}
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attribute_hidden long int
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__math_invalidf_li (long int x)
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{
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float y = 0.0f / 0.0f;
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math_force_eval (y);
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return with_errnof_li (x, EDOM);
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}
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@ -0,0 +1,38 @@
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/* Get integer exponent of a floating-point value.
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Copyright (C) 1999-2025 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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static inline RET_TYPE
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IMPL_NAME (float x)
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{
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uint32_t ux = asuint (x);
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int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
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if (__glibc_unlikely (ex == 0))
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{
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/* Zero or subnormal.
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Clear sign and exponent. */
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ux <<= 1 + EXPONENT_WIDTH;
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if (ux == 0)
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return RET_INVALID (RET_LOGB0);
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/* subnormal */
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return (RET_TYPE)-127 - stdc_leading_zeros (ux);
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}
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if (__glibc_unlikely (ex == EXPONENT_MASK >> MANTISSA_WIDTH))
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/* NaN or Inf */
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return RET_INVALID (ux << (1 + EXPONENT_WIDTH) ? RET_LOGBNAN : RET_LOGMAX);
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return ex - 127;
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}
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@ -0,0 +1,53 @@
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/* Get integer exponent of a floating-point value.
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Copyright (C) 1999-2025 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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#include <limits.h>
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#include <math.h>
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#include <stdbit.h>
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#include <libm-alias-float.h>
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#include <math-type-macros-float.h>
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#include "math_config.h"
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#ifdef DEF_AS_LLOGBF
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# define DECL_NAME __llogb
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# define FUNC_NAME llogb
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# define RET_TYPE long int
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# define RET_LOGB0 FP_LLOGB0
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# define RET_LOGBNAN FP_LLOGBNAN
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# define RET_LOGMAX LONG_MAX
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# define RET_INVALID __math_invalidf_li
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#else
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# define DECL_NAME __ilogb
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# define FUNC_NAME ilogb
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# define RET_TYPE int
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# define RET_LOGB0 FP_ILOGB0
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# define RET_LOGBNAN FP_ILOGBNAN
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# define RET_LOGMAX INT_MAX
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# define RET_INVALID __math_invalidf_i
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#endif
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#define __IMPL_NAME(x,y) x ## _ ## y
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#define _IMPL_NAME(x,y) __IMPL_NAME(x,y)
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#define IMPL_NAME _IMPL_NAME(FUNC_NAME, impl)
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#include <w_ilogbf-impl.h>
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RET_TYPE
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M_DECL_FUNC (DECL_NAME) (float x)
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{
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return IMPL_NAME (x);
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}
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libm_alias_float (DECL_NAME, FUNC_NAME);
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#define DEF_AS_LLOGBF
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#include "w_ilogbf.c"
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@ -1,39 +1 @@
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/* __ieee754_ilogbf(). LoongArch version.
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Copyright (C) 2022-2025 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 <fpu_control.h>
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int
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__ieee754_ilogbf (float x)
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{
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int x_cond;
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asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
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if (__glibc_unlikely (x_cond & _FCLASS_ZERO))
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return FP_ILOGB0;
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else if (__glibc_unlikely (x_cond & ( _FCLASS_NAN | _FCLASS_INF)))
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return FP_ILOGBNAN;
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else
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{
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asm volatile ("fabs.s \t%0, %1" : "=f" (x) : "f" (x));
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asm volatile ("flogb.s \t%0, %1" : "=f" (x) : "f" (x));
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return x;
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}
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}
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/* ilogbf is implemented at w_ilogbf.c */
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@ -0,0 +1,37 @@
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/* Get integer exponent of a floating-point value. LoongArch version.
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Copyright (C) 2022-2025 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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#include <fpu_control.h>
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static inline RET_TYPE
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IMPL_NAME (float x)
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{
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int x_cond;
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asm volatile ("fclass.s \t%0, %1" : "=f" (x_cond) : "f" (x));
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if (__glibc_unlikely (x_cond & _FCLASS_ZERO))
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return RET_INVALID (RET_LOGB0);
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else if (__glibc_unlikely (x_cond & ( _FCLASS_NAN | _FCLASS_INF)))
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return RET_INVALID (RET_LOGBNAN);
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else
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{
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asm volatile ("fabs.s \t%0, %1" : "=f" (x) : "f" (x));
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asm volatile ("flogb.s \t%0, %1" : "=f" (x) : "f" (x));
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return x;
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}
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}
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@ -0,0 +1,2 @@
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#include <math-type-macros-float.h>
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#include <w_ilogb_template.c>
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@ -0,0 +1,2 @@
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#include <math-type-macros-float.h>
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#include <w_llogb_template.c>
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@ -0,0 +1,41 @@
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/* Get integer exponent of a floating-point value.
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Copyright (C) 1999-2025 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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#include <limits.h>
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#include <math.h>
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#include <stdbit.h>
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#include "sysdeps/ieee754/flt-32/math_config.h"
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int
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__ieee754_ilogbf (float x)
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{
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uint32_t ux = asuint (x);
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int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
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if (ex == 0) /* zero or subnormal */
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{
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/* Clear sign and exponent. */
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ux <<= 1 + EXPONENT_WIDTH;
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if (ux == 0)
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return FP_ILOGB0;
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/* sbunormal */
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return -127 - stdc_leading_zeros (ux);
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}
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if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
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return ux << (1 + EXPONENT_WIDTH) ? FP_ILOGBNAN : INT_MAX;
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return ex - 127;
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}
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@ -0,0 +1,2 @@
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#include <math-type-macros-float.h>
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#include <w_ilogb_template.c>
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@ -0,0 +1,2 @@
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#include <math-type-macros-float.h>
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#include <w_llogb_template.c>
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