1 /* ix87 specific implementation of exp(x)-1.
2 Copyright (C) 1996, 1997, 2005 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
5 Based on code by John C. Bowman <bowman@ipp-garching.mpg.de>.
6 Corrections by H.J. Lu (hjl@gnu.ai.mit.edu), 1997.
8 The GNU C Library is free software; you can redistribute it and/or
9 modify it under the terms of the GNU Lesser General Public
10 License as published by the Free Software Foundation; either
11 version 2.1 of the License, or (at your option) any later version.
13 The GNU C Library is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Lesser General Public License for more details.
18 You should have received a copy of the GNU Lesser General Public
19 License along with the GNU C Library; if not, write to the Free
20 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
23 /* Using: e^x - 1 = 2^(x * log2(e)) - 1 */
26 #include <machine/asm.h>
34 ASM_TYPE_DIRECTIVE(minus1,@object)
36 ASM_SIZE_DIRECTIVE(minus1)
37 ASM_TYPE_DIRECTIVE(one,@object)
39 ASM_SIZE_DIRECTIVE(one)
40 ASM_TYPE_DIRECTIVE(l2e,@object)
41 l2e: .tfloat 1.442695040888963407359924681002
42 ASM_SIZE_DIRECTIVE(l2e)
45 #define MO(op) op##@GOTOFF(%edx)
52 movzwl 4+6(%esp), %eax
53 xorb $0x80, %ah // invert sign bit (now 1 is "positive")
54 cmpl $0xc086, %eax // is num >= 704?
55 jae HIDDEN_JUMPTARGET (__exp)
58 fxam // Is NaN or +-Inf?
63 je 3f // If +-0, jump.
68 je 2f // If +-Inf, jump.
70 fldt MO(l2e) // log2(e) : x
72 fld %st // log2(e)*x : log2(e)*x
73 frndint // int(log2(e)*x) : log2(e)*x
74 fsubr %st, %st(1) // int(log2(e)*x) : fract(log2(e)*x)
75 fxch // fract(log2(e)*x) : int(log2(e)*x)
76 f2xm1 // 2^fract(log2(e)*x)-1 : int(log2(e)*x)
77 fscale // 2^(log2(e)*x)-2^int(log2(e)*x) : int(log2(e)*x)
78 fxch // int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
79 fldl MO(one) // 1 : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
80 fscale // 2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
81 fsubrl MO(one) // 1-2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
82 fstp %st(1) // 1-2^int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
83 fsubrp %st, %st(1) // 2^(log2(e)*x)
86 2: testl $0x200, %eax // Test sign.
87 jz 3f // If positive, jump.
89 fldl MO(minus1) // Set result to -1.0.
92 weak_alias (__expm1, expm1)