1 /* ix87 specific implementation of pow function.
2 Copyright (C) 1996-2017 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>
21 #include <i386-math-asm.h>
23 .section .rodata.cst8,"aM",@progbits,8
28 ASM_SIZE_DIRECTIVE(one)
31 ASM_SIZE_DIRECTIVE(limit)
33 p31: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x41
34 ASM_SIZE_DIRECTIVE(p31)
36 .section .rodata.cst16,"aM",@progbits,16
39 .type infinity,@object
42 .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
43 ASM_SIZE_DIRECTIVE(infinity)
46 ASM_SIZE_DIRECTIVE(zero)
47 .type 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)
57 # define MO(op) op##@GOTOFF(%ecx)
58 # define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
61 # define MOX(op,x,f) op(,x,f)
76 cmpb $0x40, %ah // is y == 0 ?
79 cmpb $0x05, %ah // is y == ±inf ?
82 cmpb $0x01, %ah // is y == NaN ?
88 cfi_adjust_cfa_offset (4)
105 /* fistpl raises invalid exception for |y| >= 1L<<31. */
108 fcompl MO(p31) // y : x
113 /* First see whether `y' is a natural number. In this case we
114 can use a more precise algorithm. */
116 fistpl (%esp) // y : x
117 fildl (%esp) // int(y) : y : x
118 fucomp %st(1) // y : x
123 /* OK, we have an integer value for y. */
125 cfi_adjust_cfa_offset (-4)
128 jns 4f // y >= 0, jump
129 fdivrl MO(one) // 1/x (now referred to as x)
131 4: fldl MO(one) // 1 : x
134 /* If y is even, take the absolute value of x. Otherwise,
135 ensure all intermediate values that might overflow have the
145 fmul %st(1) // x : ST*x
147 5: fld %st // x : x : ST*x
148 fabs // |x| : x : ST*x
149 fmulp // |x|*x : ST*x
153 FLT_NARROW_EVAL_UFLOW_NONNAN
157 30: flds 4(%esp) // x : y
158 fldl MO(one) // 1.0 : x : y
159 fucomp %st(1) // x : y
167 cfi_adjust_cfa_offset (4)
169 2: /* y is a large integer (so even). */
174 3: /* y is a real number. */
176 fldl MO(one) // 1.0 : x : y
177 fldl MO(limit) // 0.29 : 1.0 : x : y
178 fld %st(2) // x : 0.29 : 1.0 : x : y
179 fsub %st(2) // x-1 : 0.29 : 1.0 : x : y
180 fabs // |x-1| : 0.29 : 1.0 : x : y
181 fucompp // 1.0 : x : y
186 fsub %st(1) // x-1 : 1.0 : y
187 fyl2xp1 // log2(x) : y
190 7: fyl2x // log2(x) : y
191 8: fmul %st(1) // y*log2(x) : y
192 fst %st(1) // y*log2(x) : y*log2(x)
193 frndint // int(y*log2(x)) : y*log2(x)
194 fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
195 fxch // fract(y*log2(x)) : int(y*log2(x))
196 f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
197 faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
198 fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
200 cfi_adjust_cfa_offset (-4)
201 fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
202 FLT_NARROW_EVAL_UFLOW_NONNAN
206 cfi_adjust_cfa_offset (4)
208 cfi_adjust_cfa_offset (-4)
214 11: fstp %st(0) // pop y
220 12: fstp %st(0) // pop y
222 flds 4(%esp) // x : 1
224 fucompp // < 1, == 1, or > 1
228 je 13f // jump if x is NaN
231 je 14f // jump if |x| == 1
236 fldl MOX(inf_zero, %edx, 4)
244 13: flds 4(%esp) // load x == NaN
247 cfi_adjust_cfa_offset (4)
252 jz 16f // jump if x == +inf
254 // fistpl raises invalid exception for |y| >= 1L<<31, so test
255 // that (in which case y is certainly even) before testing
264 // We must find out whether y is an odd integer.
267 fildl (%esp) // int(y) : y
273 // OK, the value is an integer.
275 cfi_adjust_cfa_offset (-4)
277 jz 18f // jump if not odd
278 // It's an odd integer.
280 fldl MOX(minf_mzero, %edx, 8)
283 cfi_adjust_cfa_offset (4)
287 cfi_adjust_cfa_offset (-4)
291 fldl MOX(inf_zero, %eax, 1)
294 cfi_adjust_cfa_offset (4)
296 17: shll $30, %edx // sign bit for y in right position
298 cfi_adjust_cfa_offset (-4)
300 fldl MOX(inf_zero, %edx, 8)
303 cfi_adjust_cfa_offset (4)
310 // x is ±0 and y is < 0. We must find out whether y is an odd integer.
314 // fistpl raises invalid exception for |y| >= 1L<<31, so test
315 // that (in which case y is certainly even) before testing
326 fildl (%esp) // int(y) : y
332 // OK, the value is an integer.
334 cfi_adjust_cfa_offset (-4)
336 jz 27f // jump if not odd
337 // It's an odd integer.
338 // Raise divide-by-zero exception and get minus infinity value.
344 cfi_adjust_cfa_offset (4)
347 cfi_adjust_cfa_offset (-4)
348 27: // Raise divide-by-zero exception and get infinity value.
353 cfi_adjust_cfa_offset (4)
355 // x is ±0 and y is > 0. We must find out whether y is an odd integer.
359 // fistpl raises invalid exception for |y| >= 1L<<31, so test
360 // that (in which case y is certainly even) before testing
369 fildl (%esp) // int(y) : y
375 // OK, the value is an integer.
377 cfi_adjust_cfa_offset (-4)
379 jz 24f // jump if not odd
380 // It's an odd integer.
384 cfi_adjust_cfa_offset (4)
386 23: addl $4, %esp // Don't use pop.
387 cfi_adjust_cfa_offset (-4)
392 strong_alias (__ieee754_powf, __powf_finite)