sysdeps/i386/fpu/s_expm1f.S

   1 /* ix87 specific implementation of exp(x)-1.
   2    Copyright (C) 1996-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   5    Based on code by John C. Bowman <bowman@ipp-garching.mpg.de>.
   6    Corrections by H.J. Lu (hjl@gnu.ai.mit.edu), 1997.
   7
   8    The GNU C Library is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU Lesser General Public
  10    License as published by the Free Software Foundation; either
  11    version 2.1 of the License, or (at your option) any later version.
  12
  13    The GNU C Library is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16    Lesser General Public License for more details.
  17
  18    You should have received a copy of the GNU Lesser General Public
  19    License along with the GNU C Library; if not, see
  20    <http://www.gnu.org/licenses/>.  */
  21
  22         /* Using: e^x - 1 = 2^(x * log2(e)) - 1 */
  23
  24 #include <sysdep.h>
  25 #include <machine/asm.h>
  26
  27         .section .rodata
  28
  29         .align ALIGNARG(4)
  30         .type minus1,@object
  31 minus1: .double -1.0
  32         ASM_SIZE_DIRECTIVE(minus1)
  33         .type one,@object
  34 one:    .double 1.0
  35         ASM_SIZE_DIRECTIVE(one)
  36         .type l2e,@object
  37 l2e:    .tfloat 1.442695040888963407359924681002
  38         ASM_SIZE_DIRECTIVE(l2e)
  39
  40 #ifdef PIC
  41 #define MO(op) op##@GOTOFF(%edx)
  42 #else
  43 #define MO(op) op
  44 #endif
  45
  46         .text
  47 ENTRY(__expm1f)
  48         movzwl  4+2(%esp), %eax
  49         xorb    $0x80, %ah      // invert sign bit (now 1 is "positive")
  50         cmpl    $0xc2b1, %eax   // is num >= 88.5?
  51         jae     HIDDEN_JUMPTARGET (__expf)
  52
  53         flds    4(%esp)         // x
  54         fxam                    // Is NaN, +-Inf or +-0?
  55         xorb    $0x80, %ah
  56         cmpl    $0xc190, %eax   // is num <= -18.0?
  57         fstsw   %ax
  58         movb    $0x45, %ch
  59         jb      4f
  60
  61         // Below -18.0 (may be -NaN or -Inf).
  62         andb    %ah, %ch
  63 #ifdef  PIC
  64         LOAD_PIC_REG (dx)
  65 #endif
  66         cmpb    $0x01, %ch
  67         je      5f              // If -NaN, jump.
  68         jmp     2f              // -large, possibly -Inf.
  69
  70 4:      // In range -18.0 to 88.5 (may be +-0 but not NaN or +-Inf).
  71         andb    %ah, %ch
  72         cmpb    $0x40, %ch
  73         je      3f              // If +-0, jump.
  74 #ifdef  PIC
  75         LOAD_PIC_REG (dx)
  76 #endif
  77
  78 5:      fldt    MO(l2e)         // log2(e) : x
  79         fmulp                   // log2(e)*x
  80         fld     %st             // log2(e)*x : log2(e)*x
  81         // Set round-to-nearest temporarily.
  82         subl    $8, %esp
  83         cfi_adjust_cfa_offset (8)
  84         fstcw   4(%esp)
  85         movl    $0xf3ff, %ecx
  86         andl    4(%esp), %ecx
  87         movl    %ecx, (%esp)
  88         fldcw   (%esp)
  89         frndint                 // int(log2(e)*x) : log2(e)*x
  90         fldcw   4(%esp)
  91         addl    $8, %esp
  92         cfi_adjust_cfa_offset (-8)
  93         fsubr   %st, %st(1)     // int(log2(e)*x) : fract(log2(e)*x)
  94         fxch                    // fract(log2(e)*x) : int(log2(e)*x)
  95         f2xm1                   // 2^fract(log2(e)*x)-1 : int(log2(e)*x)
  96         fscale                  // 2^(log2(e)*x)-2^int(log2(e)*x) : int(log2(e)*x)
  97         fxch                    // int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
  98         fldl    MO(one)         // 1 : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
  99         fscale                  // 2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
 100         fsubrl  MO(one)         // 1-2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
 101         fstp    %st(1)          // 1-2^int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
 102         fsubrp  %st, %st(1)     // 2^(log2(e)*x)
 103         ret
 104
 105 2:      fstp    %st
 106         fldl    MO(minus1)      // Set result to -1.0.
 107 3:      ret
 108 END(__expm1f)
 109 weak_alias (__expm1f, expm1f)