reactos/lib/sdk/crt/math/i386/pow_asm.s

   1 /*
   2  * COPYRIGHT:         See COPYING in the top level directory
   3  * PROJECT:           ReactOS kernel
   4  * PURPOSE:           Run-Time Library
   5  * FILE:              lib/rtl/i386/pow.S
   6  * PROGRAMER:         Alex Ionescu (alex@relsoft.net)
   7  *
   8  * Copyright (C) 2002 Michael Ringgaard.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  *
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. Neither the name of the project nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23
  24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES// LOSS OF USE, DATA, OR PROFITS// OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 .globl _pow
  38
  39  /* DATA ********************************************************************/
  40
  41 fzero:
  42         .long   0                       // Floating point zero
  43         .long   0                       // Floating point zero
  44
  45 .intel_syntax noprefix
  46
  47 /* FUNCTIONS ***************************************************************/
  48
  49 _pow:
  50         push    ebp
  51         mov     ebp,esp
  52         sub     esp,12                  // Allocate temporary space
  53         push    edi                     // Save register edi
  54         push    eax                     // Save register eax
  55         mov     dword ptr [ebp-12],0    // Set negation flag to zero
  56         fld     qword ptr [ebp+16]      // Load real from stack
  57         fld     qword ptr [ebp+8]       // Load real from stack
  58         mov     edi,offset flat:fzero   // Point to real zero
  59         fcom    qword ptr [edi]         // Compare x with zero
  60         fstsw   ax                      // Get the FPU status word
  61         mov     al,ah                   // Move condition flags to AL
  62         lahf                            // Load Flags into AH
  63         and     al,    0b01000101       // Isolate  C0, C2 and C3
  64         and     ah,    0b10111010       // Turn off CF, PF and ZF
  65         or      ah,al                   // Set new  CF, PF and ZF
  66         sahf                            // Store AH into Flags
  67         jb      __fpow1                 // Re-direct if x < 0
  68         ja      __fpow2                 // Re-direct if x > 0
  69         fxch                            // Swap st, st(1)
  70         fcom    qword ptr [edi]         // Compare y with zero
  71         fxch                            // Restore x as top of stack
  72         fstsw   ax                      // Get the FPU status word
  73         mov     al,ah                   // Move condition flags to AL
  74         lahf                            // Load Flags into AH
  75         and     al,    0b01000101       // Isolate  C0, C2 and C3
  76         and     ah,    0b10111010       // Turn off CF, PF and ZF
  77         or      ah,al                   // Set new  CF, PF and ZF
  78         sahf                            // Store AH into Flags
  79         jmp     __fpow2                 // Re-direct
  80 __fpow1:        fxch                            // Put y on top of stack
  81         fld    st                       // Duplicate y as st(1)
  82         frndint                         // Round to integer
  83         fxch                            // Put y on top of stack
  84         fcomp                           // y = int(y) ?
  85         fstsw   ax                      // Get the FPU status word
  86         mov     al,ah                   // Move condition flags to AL
  87         lahf                            // Load Flags into AH
  88         and     al,    0b01000101       // Isolate  C0, C2 and C3
  89         and     ah,    0b10111010       // Turn off CF, PF and ZF
  90         or      ah,al                   // Set new  CF, PF and ZF
  91         sahf                            // Store AH into Flags
  92         jne      __fpow4                 // Proceed if y = int(y)
  93         fist    dword ptr [ebp-12]      // Store y as integer
  94         and     dword ptr [ebp-12],1    // Set bit if y is odd
  95         fxch                            // Put x on top of stack
  96         fabs                            // x = |x|
  97 __fpow2:        fldln2                          // Load log base e of 2
  98         fxch    st(1)                   // Exchange st, st(1)
  99         fyl2x                           // Compute the natural log(x)
 100         fmulp                           // Compute y * ln(x)
 101         fldl2e                          // Load log base 2(e)
 102         fmulp   st(1),st                // Multiply x * log base 2(e)
 103         fst     st(1)                   // Push result
 104         frndint                         // Round to integer
 105         fsub    st(1),st                // Subtract
 106         fxch                            // Exchange st, st(1)
 107         f2xm1                           // Compute 2 to the (x - 1)
 108         fld1                            // Load real number 1
 109         faddp                           // 2 to the x
 110         fscale                          // Scale by power of 2
 111         fstp    st(1)                   // Set new stack top and pop
 112         test    dword ptr [ebp-12],1    // Negation required ?
 113         jz      __fpow3                 // No, re-direct
 114         fchs                            // Negate the result
 115 __fpow3:        fstp    qword ptr [ebp-8]       // Save (double)pow(x, y)
 116         fld     qword ptr [ebp-8]       // Load (double)pow(x, y)
 117 __fpow4:        pop     eax                     // Restore register eax
 118         pop     edi                     // Restore register edi
 119         mov     esp,ebp                 // Deallocate temporary space
 120         pop     ebp
 121         ret