diff options
Diffstat (limited to 'sysdeps/libm-i387/e_pow.S')
| -rw-r--r-- | sysdeps/libm-i387/e_pow.S | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/sysdeps/libm-i387/e_pow.S b/sysdeps/libm-i387/e_pow.S new file mode 100644 index 0000000..f6c7562 --- /dev/null +++ b/sysdeps/libm-i387/e_pow.S @@ -0,0 +1,120 @@ +/* ix87 specific implementation of pow function. + Copyright (C) 1996 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include <machine/asm.h> + +#ifdef __ELF__ + .section .rodata +#else + .text +#endif + + .align ALIGNARG(4) + ASM_TYPE_DIRECTIVE(one,@object) +one: .double 1.0 + ASM_SIZE_DIRECTIVE(one) + ASM_TYPE_DIRECTIVE(limit,@object) +limit: .double 0.29 + ASM_SIZE_DIRECTIVE(limit) + +#ifdef PIC +#define MO(op) op##@GOTOFF(%ecx) +#else +#define MO(op) op +#endif + + .text +ENTRY(__ieee754_pow) + fldl 4(%esp) // x + fldl 12(%esp) // y : x + +#ifdef PIC + call 1f +1: popl %ecx + addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx +#endif + subl $8,%esp + + /* First see whether `y' is a natural number. In this case we + can use a more precise algorithm. */ + fld %st // y : y : x + fistpll (%esp) // y : x + fildll (%esp) // int(y) : y : x + fucomp %st(1) // y : x + fnstsw + sahf + jne 2f + + /* OK, we have an integer value for y. */ + ftst // y : x + fstp %st(0) // x + fnstsw + sahf + popl %eax + popl %edx + jnc 4f // y >= 0, jump + fdivrl MO(one) // 1/x (now referred to as x) + negl %eax + adcl $0, %edx + negl %edx +4: fldl MO(one) // 1 : x + fxch + +6: shrdl $1, %edx, %eax + jnc 5f + fxch + fmul %st(1) // x : ST*x + fxch +5: fmul %st(0), %st // x*x : ST*x + movl %eax, %ecx + orl %edx, %ecx + jnz 6b + fstp %st(0) // ST*x + ret + + .align ALIGNARG(4) +2: /* y is a real number. */ + fxch // x : y + fldl MO(one) // 1.0 : x : y + fld %st(1) // x : 1.0 : x : y + fsub %st(1) // x-1 : 1.0 : x : y + fabs // |x-1| : 1.0 : x : y + fcompl MO(limit) // 1.0 : x : y + fnstsw + fxch // x : 1.0 : y + sahf + ja 7f + fsub %st(1) // x-1 : 1.0 : y + fyl2xp1 // log2(x) : y + jmp 8f + +7: fyl2x // log2(x) : y +8: fmul %st(1) // y*log2(x) : y + fst %st(1) // y*log2(x) : y*log2(x) + frndint // int(y*log2(x)) : y*log2(x) + fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x)) + fxch // fract(y*log2(x)) : int(y*log2(x)) + f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x)) + faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x)) + fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x)) + addl $8, %esp + fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x)) + ret +END(__ieee754_pow) |