1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996, 1997, 1999, 2001, 2004 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)
51 ASM_TYPE_DIRECTIVE(p31,@object)
52 p31: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x41
53 ASM_SIZE_DIRECTIVE(p31)
56 #define MO(op) op##@GOTOFF(%ecx)
57 #define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
60 #define MOX(op,x,f) op(,x,f)
71 addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx
77 cmpb $0x40, %ah // is y == 0 ?
80 cmpb $0x05, %ah // is y == ±inf ?
83 cmpb $0x01, %ah // is y == NaN ?
102 /* fistpl raises invalid exception for |y| >= 1L<<31. */
105 fcompl MO(p31) // y : x
110 /* First see whether `y' is a natural number. In this case we
111 can use a more precise algorithm. */
113 fistpl (%esp) // y : x
114 fildl (%esp) // int(y) : y : x
115 fucomp %st(1) // y : x
120 /* OK, we have an integer value for y. */
124 jns 4f // y >= 0, jump
125 fdivrl MO(one) // 1/x (now referred to as x)
127 4: fldl MO(one) // 1 : x
133 fmul %st(1) // x : ST*x
135 5: fmul %st(0), %st // x*x : ST*x
142 30: flds 4(%esp) // x : y
143 fldl MO(one) // 1.0 : x : y
144 fucomp %st(1) // x : y
153 2: /* y is a real number. */
155 fldl MO(one) // 1.0 : x : y
156 fld %st(1) // x : 1.0 : x : y
157 fsub %st(1) // x-1 : 1.0 : x : y
158 fabs // |x-1| : 1.0 : x : y
159 fcompl MO(limit) // 1.0 : x : y
164 fsub %st(1) // x-1 : 1.0 : y
165 fyl2xp1 // log2(x) : y
168 7: fyl2x // log2(x) : y
169 8: fmul %st(1) // y*log2(x) : y
170 fst %st(1) // y*log2(x) : y*log2(x)
171 frndint // int(y*log2(x)) : y*log2(x)
172 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
173 fxch // fract(y*log2(x)) : int(y*log2(x))
174 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
175 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
176 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
178 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
184 11: fstp %st(0) // pop y
190 12: fstp %st(0) // pop y
193 fcompl MO(one) // < 1, == 1, or > 1
197 je 13f // jump if x is NaN
200 je 14f // jump if |x| == 1
205 fldl MOX(inf_zero, %edx, 4)
213 13: flds 4(%esp) // load x == NaN
220 jz 16f // jump if x == +inf
222 // We must find out whether y is an odd integer.
225 fildl (%esp) // int(y) : y
231 // OK, the value is an integer, but is the number of bits small
232 // enough so that all are coming from the mantissa?
235 jz 18f // jump if not odd
240 155: cmpl $0x01000000, %eax
241 ja 18f // does not fit in mantissa bits
242 // It's an odd integer.
244 fldl MOX(minf_mzero, %edx, 8)
253 fldl MOX(inf_zero, %eax, 1)
257 17: shll $30, %edx // sign bit for y in right position
260 fldl MOX(inf_zero, %edx, 8)
269 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
275 fildl (%esp) // int(y) : y
281 // OK, the value is an integer, but is the number of bits small
282 // enough so that all are coming from the mantissa?
285 jz 27f // jump if not odd
286 cmpl $0xff000000, %edx
287 jbe 27f // does not fit in mantissa bits
288 // It's an odd integer.
289 // Raise divide-by-zero exception and get minus infinity value.
297 27: // Raise divide-by-zero exception and get infinity value.
303 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
309 fildl (%esp) // int(y) : y
315 // OK, the value is an integer, but is the number of bits small
316 // enough so that all are coming from the mantissa?
319 jz 24f // jump if not odd
320 cmpl $0xff000000, %edx
321 jae 24f // does not fit in mantissa bits
322 // It's an odd integer.
327 23: addl $4, %esp // Don't use pop.