1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996-2015 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 p31: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x41
33 ASM_SIZE_DIRECTIVE(p31)
35 .section .rodata.cst16,"aM",@progbits,16
38 .type infinity,@object
41 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
42 ASM_SIZE_DIRECTIVE(infinity)
45 ASM_SIZE_DIRECTIVE(zero)
46 .type minf_mzero,@object
49 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
51 .byte 0, 0, 0, 0, 0, 0, 0, 0x80
52 ASM_SIZE_DIRECTIVE(minf_mzero)
55 # define MO(op) op##@GOTOFF(%ecx)
56 # define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
59 # define MOX(op,x,f) op(,x,f)
74 cmpb $0x40, %ah // is y == 0 ?
77 cmpb $0x05, %ah // is y == ±inf ?
80 cmpb $0x01, %ah // is y == NaN ?
86 cfi_adjust_cfa_offset (4)
103 /* fistpl raises invalid exception for |y| >= 1L<<31. */
106 fcompl MO(p31) // y : x
111 /* First see whether `y' is a natural number. In this case we
112 can use a more precise algorithm. */
114 fistpl (%esp) // y : x
115 fildl (%esp) // int(y) : y : x
116 fucomp %st(1) // y : x
121 /* OK, we have an integer value for y. */
123 cfi_adjust_cfa_offset (-4)
126 jns 4f // y >= 0, jump
127 fdivrl MO(one) // 1/x (now referred to as x)
129 4: fldl MO(one) // 1 : x
132 /* If y is even, take the absolute value of x. Otherwise,
133 ensure all intermediate values that might overflow have the
143 fmul %st(1) // x : ST*x
145 5: fld %st // x : x : ST*x
146 fabs // |x| : x : ST*x
147 fmulp // |x|*x : ST*x
154 30: flds 4(%esp) // x : y
155 fldl MO(one) // 1.0 : x : y
156 fucomp %st(1) // x : y
164 cfi_adjust_cfa_offset (4)
166 2: /* y is a large integer (so even). */
171 3: /* y is a real number. */
173 fldl MO(one) // 1.0 : x : y
174 fldl MO(limit) // 0.29 : 1.0 : x : y
175 fld %st(2) // x : 0.29 : 1.0 : x : y
176 fsub %st(2) // x-1 : 0.29 : 1.0 : x : y
177 fabs // |x-1| : 0.29 : 1.0 : x : y
178 fucompp // 1.0 : x : y
183 fsub %st(1) // x-1 : 1.0 : y
184 fyl2xp1 // log2(x) : y
187 7: fyl2x // log2(x) : y
188 8: fmul %st(1) // y*log2(x) : y
189 fst %st(1) // y*log2(x) : y*log2(x)
190 frndint // int(y*log2(x)) : y*log2(x)
191 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
192 fxch // fract(y*log2(x)) : int(y*log2(x))
193 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
194 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
195 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
197 cfi_adjust_cfa_offset (-4)
198 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
204 11: fstp %st(0) // pop y
210 12: fstp %st(0) // pop y
212 flds 4(%esp) // x : 1
214 fucompp // < 1, == 1, or > 1
218 je 13f // jump if x is NaN
221 je 14f // jump if |x| == 1
226 fldl MOX(inf_zero, %edx, 4)
234 13: flds 4(%esp) // load x == NaN
237 cfi_adjust_cfa_offset (4)
242 jz 16f // jump if x == +inf
244 // fistpl raises invalid exception for |y| >= 1L<<31, so test
245 // that (in which case y is certainly even) before testing
254 // We must find out whether y is an odd integer.
257 fildl (%esp) // int(y) : y
263 // OK, the value is an integer.
265 cfi_adjust_cfa_offset (-4)
267 jz 18f // jump if not odd
268 // It's an odd integer.
270 fldl MOX(minf_mzero, %edx, 8)
273 cfi_adjust_cfa_offset (4)
277 cfi_adjust_cfa_offset (-4)
281 fldl MOX(inf_zero, %eax, 1)
284 cfi_adjust_cfa_offset (4)
286 17: shll $30, %edx // sign bit for y in right position
288 cfi_adjust_cfa_offset (-4)
290 fldl MOX(inf_zero, %edx, 8)
293 cfi_adjust_cfa_offset (4)
300 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
304 // fistpl raises invalid exception for |y| >= 1L<<31, so test
305 // that (in which case y is certainly even) before testing
316 fildl (%esp) // int(y) : y
322 // OK, the value is an integer.
324 cfi_adjust_cfa_offset (-4)
326 jz 27f // jump if not odd
327 // It's an odd integer.
328 // Raise divide-by-zero exception and get minus infinity value.
334 cfi_adjust_cfa_offset (4)
337 cfi_adjust_cfa_offset (-4)
338 27: // Raise divide-by-zero exception and get infinity value.
343 cfi_adjust_cfa_offset (4)
345 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
349 // fistpl raises invalid exception for |y| >= 1L<<31, so test
350 // that (in which case y is certainly even) before testing
359 fildl (%esp) // int(y) : y
365 // OK, the value is an integer.
367 cfi_adjust_cfa_offset (-4)
369 jz 24f // jump if not odd
370 // It's an odd integer.
374 cfi_adjust_cfa_offset (4)
376 23: addl $4, %esp // Don't use pop.
377 cfi_adjust_cfa_offset (-4)
382 strong_alias (__ieee754_powf, __powf_finite)