1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996-2014 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, see
18 <http://www.gnu.org/licenses/>. */
20 #include <machine/asm.h>
22 .section .rodata.cst8,"aM",@progbits,8
27 ASM_SIZE_DIRECTIVE(one)
30 ASM_SIZE_DIRECTIVE(limit)
32 p63: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x43
33 ASM_SIZE_DIRECTIVE(p63)
35 p10: .byte 0, 0, 0, 0, 0, 0, 0x90, 0x40
36 ASM_SIZE_DIRECTIVE(p10)
38 .section .rodata.cst16,"aM",@progbits,16
41 .type infinity,@object
44 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
45 ASM_SIZE_DIRECTIVE(infinity)
48 ASM_SIZE_DIRECTIVE(zero)
49 .type minf_mzero,@object
52 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
54 .byte 0, 0, 0, 0, 0, 0, 0, 0x80
55 ASM_SIZE_DIRECTIVE(minf_mzero)
58 # define MO(op) op##@GOTOFF(%ecx)
59 # define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
62 # define MOX(op,x,f) op(,x,f)
77 cmpb $0x40, %ah // is y == 0 ?
80 cmpb $0x05, %ah // is y == ±inf ?
83 cmpb $0x01, %ah // is y == NaN ?
89 cfi_adjust_cfa_offset (8)
106 /* fistpll raises invalid exception for |y| >= 1L<<63. */
109 fcompl MO(p63) // y : x
114 /* First see whether `y' is a natural number. In this case we
115 can use a more precise algorithm. */
117 fistpll (%esp) // y : x
118 fildll (%esp) // int(y) : y : x
119 fucomp %st(1) // y : x
124 /* OK, we have an integer value for y. If large enough that
125 errors may propagate out of the 11 bits excess precision, use
126 the algorithm for real exponent instead. */
129 fcompl MO(p10) // y : x
134 cfi_adjust_cfa_offset (-4)
136 cfi_adjust_cfa_offset (-4)
139 jns 4f // y >= 0, jump
140 fdivrl MO(one) // 1/x (now referred to as x)
144 4: fldl MO(one) // 1 : x
147 6: shrdl $1, %edx, %eax
150 fmul %st(1) // x : ST*x
152 5: fmul %st(0), %st // x*x : ST*x
161 30: fldl 4(%esp) // x : y
162 fldl MO(one) // 1.0 : x : y
163 fucomp %st(1) // x : y
171 cfi_adjust_cfa_offset (8)
173 cfi_adjust_cfa_offset (-8)
177 cfi_adjust_cfa_offset (8)
179 2: // y is a large integer (absolute value at least 1L<<10), but
180 // may be odd unless at least 1L<<64. So it may be necessary
181 // to adjust the sign of a negative result afterwards.
186 3: /* y is a real number. */
188 fldl MO(one) // 1.0 : x : y
189 fldl MO(limit) // 0.29 : 1.0 : x : y
190 fld %st(2) // x : 0.29 : 1.0 : x : y
191 fsub %st(2) // x-1 : 0.29 : 1.0 : x : y
192 fabs // |x-1| : 0.29 : 1.0 : x : y
193 fucompp // 1.0 : x : y
198 fsub %st(1) // x-1 : 1.0 : y
199 fyl2xp1 // log2(x) : y
202 7: fyl2x // log2(x) : y
203 8: fmul %st(1) // y*log2(x) : y
204 fst %st(1) // y*log2(x) : y*log2(x)
205 frndint // int(y*log2(x)) : y*log2(x)
206 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
207 fxch // fract(y*log2(x)) : int(y*log2(x))
208 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
209 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
210 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
211 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
214 // x is negative. If y is an odd integer, negate the result.
215 fldl 20(%esp) // y : abs(result)
216 fld %st // y : y : abs(result)
217 fabs // |y| : y : abs(result)
218 fcompl MO(p63) // y : abs(result)
223 // We must find out whether y is an odd integer.
224 fld %st // y : y : abs(result)
225 fistpll (%esp) // y : abs(result)
226 fildll (%esp) // int(y) : y : abs(result)
227 fucompp // abs(result)
232 // OK, the value is an integer, but is it odd?
234 cfi_adjust_cfa_offset (-4)
236 cfi_adjust_cfa_offset (-4)
238 jz 290f // jump if not odd
239 // It's an odd integer.
242 cfi_adjust_cfa_offset (8)
243 291: fstp %st(0) // abs(result)
245 cfi_adjust_cfa_offset (-8)
251 11: fstp %st(0) // pop y
257 12: fstp %st(0) // pop y
259 fldl 4(%esp) // x : 1
261 fucompp // < 1, == 1, or > 1
265 je 13f // jump if x is NaN
268 je 14f // jump if |x| == 1
273 fldl MOX(inf_zero, %edx, 4)
281 13: fldl 4(%esp) // load x == NaN
284 cfi_adjust_cfa_offset (8)
289 jz 16f // jump if x == +inf
291 // fistpll raises invalid exception for |y| >= 1L<<63, so test
292 // that (in which case y is certainly even) before testing
301 // We must find out whether y is an odd integer.
304 fildll (%esp) // int(y) : y
310 // OK, the value is an integer.
312 cfi_adjust_cfa_offset (-4)
314 cfi_adjust_cfa_offset (-4)
316 jz 18f // jump if not odd
317 // It's an odd integer.
319 fldl MOX(minf_mzero, %edx, 8)
322 cfi_adjust_cfa_offset (8)
326 cfi_adjust_cfa_offset (-8)
330 fldl MOX(inf_zero, %eax, 1)
333 cfi_adjust_cfa_offset (8)
335 17: shll $30, %edx // sign bit for y in right position
337 cfi_adjust_cfa_offset (-8)
339 fldl MOX(inf_zero, %edx, 8)
342 cfi_adjust_cfa_offset (8)
349 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
353 // fistpll raises invalid exception for |y| >= 1L<<63, so test
354 // that (in which case y is certainly even) before testing
365 fildll (%esp) // int(y) : y
371 // OK, the value is an integer.
373 cfi_adjust_cfa_offset (-4)
375 cfi_adjust_cfa_offset (-4)
377 jz 27f // jump if not odd
378 // It's an odd integer.
379 // Raise divide-by-zero exception and get minus infinity value.
385 cfi_adjust_cfa_offset (8)
388 cfi_adjust_cfa_offset (-8)
389 27: // Raise divide-by-zero exception and get infinity value.
394 cfi_adjust_cfa_offset (8)
396 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
400 // fistpll raises invalid exception for |y| >= 1L<<63, so test
401 // that (in which case y is certainly even) before testing
410 fildll (%esp) // int(y) : y
416 // OK, the value is an integer.
418 cfi_adjust_cfa_offset (-4)
420 cfi_adjust_cfa_offset (-4)
422 jz 24f // jump if not odd
423 // It's an odd integer.
427 cfi_adjust_cfa_offset (8)
429 23: addl $8, %esp // Don't use 2 x pop
430 cfi_adjust_cfa_offset (-8)
435 strong_alias (__ieee754_pow, __pow_finite)