1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996, 1997, 1998, 1999, 2001 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
21 #include <machine/asm.h>
30 ASM_TYPE_DIRECTIVE(infinity,@object)
33 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
34 ASM_SIZE_DIRECTIVE(infinity)
35 ASM_TYPE_DIRECTIVE(zero,@object)
37 ASM_SIZE_DIRECTIVE(zero)
38 ASM_TYPE_DIRECTIVE(minf_mzero,@object)
41 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
43 .byte 0, 0, 0, 0, 0, 0, 0, 0x80
44 ASM_SIZE_DIRECTIVE(minf_mzero)
45 ASM_TYPE_DIRECTIVE(one,@object)
47 ASM_SIZE_DIRECTIVE(one)
48 ASM_TYPE_DIRECTIVE(limit,@object)
50 ASM_SIZE_DIRECTIVE(limit)
53 #define MO(op) op##(%rip)
67 cmpb $0x40, %ah // is y == 0 ?
70 cmpb $0x05, %ah // is y == ±inf ?
73 cmpb $0x01, %ah // is y == NaN ?
90 /* First see whether `y' is a natural number. In this case we
91 can use a more precise algorithm. */
93 fistpll -8(%rsp) // y : x
94 fildll -8(%rsp) // int(y) : y : x
95 fucomip %st(1),%st // y : x
98 /* OK, we have an integer value for y. */
103 jns 4f // y >= 0, jump
104 fdivrl MO(one) // 1/x (now referred to as x)
108 4: fldl MO(one) // 1 : x
111 6: shrdl $1, %edx, %eax
114 fmul %st(1) // x : ST*x
116 5: fmul %st(0), %st // x*x : ST*x
125 30: fldt 8(%rsp) // x : y
126 fldl MO(one) // 1.0 : x : y
127 fucomip %st(1),%st // x : y
134 2: /* y is a real number. */
136 fldl MO(one) // 1.0 : x : y
137 fld %st(1) // x : 1.0 : x : y
138 fsub %st(1) // x-1 : 1.0 : x : y
139 fabs // |x-1| : 1.0 : x : y
140 fcompl MO(limit) // 1.0 : x : y
145 fsub %st(1) // x-1 : 1.0 : y
146 fyl2xp1 // log2(x) : y
149 7: fyl2x // log2(x) : y
150 8: fmul %st(1) // y*log2(x) : y
151 fst %st(1) // y*log2(x) : y*log2(x)
152 frndint // int(y*log2(x)) : y*log2(x)
153 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
154 fxch // fract(y*log2(x)) : int(y*log2(x))
155 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
156 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
157 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
158 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
164 11: fstp %st(0) // pop y
170 12: fstp %st(0) // pop y
173 fcompl MO(one) // < 1, == 1, or > 1
177 je 13f // jump if x is NaN
180 je 14f // jump if |x| == 1
186 lea inf_zero(%rip),%rcx
189 fldl inf_zero(,%rdx, 4)
198 13: fldt 8(%rsp) // load x == NaN
205 jz 16f // jump if x == +inf
207 // We must find out whether y is an odd integer.
209 fistpll -8(%rsp) // y
210 fildll -8(%rsp) // int(y) : y
212 ffreep %st // <empty>
215 // OK, the value is an integer, but is it odd?
219 jz 18f // jump if not odd
220 // It's an odd integer.
223 lea minf_mzero(%rip),%rcx
226 fldl minf_mzero(,%rdx, 8)
236 lea inf_zero(%rip),%rcx
239 fldl inf_zero(,%rax, 1)
244 17: shll $30, %edx // sign bit for y in right position
247 lea inf_zero(%rip),%rcx
250 fldl inf_zero(,%rdx, 8)
260 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
265 fistpll -8(%rsp) // y
266 fildll -8(%rsp) // int(y) : y
268 ffreep %st // <empty>
271 // OK, the value is an integer, but is it odd?
275 jz 27f // jump if not odd
276 // It's an odd integer.
277 // Raise divide-by-zero exception and get minus infinity value.
285 27: // Raise divide-by-zero exception and get infinity value.
291 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
296 fistpll -8(%rsp) // y
297 fildll -8(%rsp) // int(y) : y
299 ffreep %st // <empty>
302 // OK, the value is an integer, but is it odd?
306 jz 24f // jump if not odd
307 // It's an odd integer.