1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996-1997, 1999, 2001, 2004, 2005, 2007, 2011-2012
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, see
19 <http://www.gnu.org/licenses/>. */
21 #include <machine/asm.h>
23 .section .rodata.cst8,"aM",@progbits,8
26 ASM_TYPE_DIRECTIVE(one,@object)
28 ASM_SIZE_DIRECTIVE(one)
29 ASM_TYPE_DIRECTIVE(limit,@object)
31 ASM_SIZE_DIRECTIVE(limit)
32 ASM_TYPE_DIRECTIVE(p31,@object)
33 p31: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x41
34 ASM_SIZE_DIRECTIVE(p31)
36 .section .rodata.cst16,"aM",@progbits,16
39 ASM_TYPE_DIRECTIVE(infinity,@object)
42 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
43 ASM_SIZE_DIRECTIVE(infinity)
44 ASM_TYPE_DIRECTIVE(zero,@object)
46 ASM_SIZE_DIRECTIVE(zero)
47 ASM_TYPE_DIRECTIVE(minf_mzero,@object)
50 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
52 .byte 0, 0, 0, 0, 0, 0, 0, 0x80
53 ASM_SIZE_DIRECTIVE(minf_mzero)
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)
75 cmpb $0x40, %ah // is y == 0 ?
78 cmpb $0x05, %ah // is y == ±inf ?
81 cmpb $0x01, %ah // is y == NaN ?
87 cfi_adjust_cfa_offset (4)
101 /* fistpl raises invalid exception for |y| >= 1L<<31. */
104 fcompl MO(p31) // y : x
109 /* First see whether `y' is a natural number. In this case we
110 can use a more precise algorithm. */
112 fistpl (%esp) // y : x
113 fildl (%esp) // int(y) : y : x
114 fucomp %st(1) // y : x
119 /* OK, we have an integer value for y. */
121 cfi_adjust_cfa_offset (-4)
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
152 cfi_adjust_cfa_offset (4)
154 2: /* y is a real number. */
156 fldl MO(one) // 1.0 : x : y
157 fldl MO(limit) // 0.29 : 1.0 : x : y
158 fld %st(2) // x : 0.29 : 1.0 : x : y
159 fsub %st(2) // x-1 : 0.29 : 1.0 : x : y
160 fabs // |x-1| : 0.29 : 1.0 : x : y
161 fucompp // 1.0 : x : y
166 fsub %st(1) // x-1 : 1.0 : y
167 fyl2xp1 // log2(x) : y
170 7: fyl2x // log2(x) : y
171 8: fmul %st(1) // y*log2(x) : y
172 fst %st(1) // y*log2(x) : y*log2(x)
173 frndint // int(y*log2(x)) : y*log2(x)
174 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
175 fxch // fract(y*log2(x)) : int(y*log2(x))
176 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
177 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
178 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
180 cfi_adjust_cfa_offset (-4)
181 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
187 11: fstp %st(0) // pop y
193 12: fstp %st(0) // pop y
195 flds 4(%esp) // x : 1
197 fucompp // < 1, == 1, or > 1
201 je 13f // jump if x is NaN
204 je 14f // jump if |x| == 1
209 fldl MOX(inf_zero, %edx, 4)
217 13: flds 4(%esp) // load x == NaN
220 cfi_adjust_cfa_offset (4)
225 jz 16f // jump if x == +inf
227 // We must find out whether y is an odd integer.
230 fildl (%esp) // int(y) : y
236 // OK, the value is an integer, but is the number of bits small
237 // enough so that all are coming from the mantissa?
239 cfi_adjust_cfa_offset (-4)
241 jz 18f // jump if not odd
246 155: cmpl $0x01000000, %eax
247 ja 18f // does not fit in mantissa bits
248 // It's an odd integer.
250 fldl MOX(minf_mzero, %edx, 8)
253 cfi_adjust_cfa_offset (4)
257 cfi_adjust_cfa_offset (-4)
261 fldl MOX(inf_zero, %eax, 1)
264 cfi_adjust_cfa_offset (4)
266 17: shll $30, %edx // sign bit for y in right position
268 cfi_adjust_cfa_offset (-4)
270 fldl MOX(inf_zero, %edx, 8)
273 cfi_adjust_cfa_offset (4)
280 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
286 fildl (%esp) // int(y) : y
292 // OK, the value is an integer, but is the number of bits small
293 // enough so that all are coming from the mantissa?
295 cfi_adjust_cfa_offset (-4)
297 jz 27f // jump if not odd
298 cmpl $0xff000000, %edx
299 jbe 27f // does not fit in mantissa bits
300 // It's an odd integer.
301 // Raise divide-by-zero exception and get minus infinity value.
307 cfi_adjust_cfa_offset (4)
310 cfi_adjust_cfa_offset (-4)
311 27: // Raise divide-by-zero exception and get infinity value.
316 cfi_adjust_cfa_offset (4)
318 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
324 fildl (%esp) // int(y) : y
330 // OK, the value is an integer, but is the number of bits small
331 // enough so that all are coming from the mantissa?
333 cfi_adjust_cfa_offset (-4)
335 jz 24f // jump if not odd
336 cmpl $0xff000000, %edx
337 jae 24f // does not fit in mantissa bits
338 // It's an odd integer.
342 cfi_adjust_cfa_offset (4)
344 23: addl $4, %esp // Don't use pop.
345 cfi_adjust_cfa_offset (-4)
350 strong_alias (__ieee754_powf, __powf_finite)