1 // Copyright 2010 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
7 // The method is based on a paper by Naoki Shibata: "Efficient evaluation
8 // methods of elementary functions suitable for SIMD computation", Proc.
9 // of International Supercomputing Conference 2010 (ISC'10), pp. 25 -- 32
10 // (May 2010). The paper is available at
11 // https://link.springer.com/article/10.1007/s00450-010-0108-2
13 // The original code and the constants below are from the author's
14 // implementation available at http://freshmeat.net/projects/sleef.
15 // The README file says, "The software is in public domain.
16 // You can use the software without any obligation."
18 // This code is a simplified version of the original.
20 #define LN2 0.6931471805599453094172321214581766 // log_e(2)
21 #define LOG2E 1.4426950408889634073599246810018920 // 1/LN2
22 #define LN2U 0.69314718055966295651160180568695068359375 // upper half LN2
23 #define LN2L 0.28235290563031577122588448175013436025525412068e-12 // lower half LN2
24 #define PosInf 0x7FF0000000000000
25 #define NegInf 0xFFF0000000000000
26 #define Overflow 7.09782712893384e+02
28 DATA exprodata<>+0(SB)/8, $0.5
29 DATA exprodata<>+8(SB)/8, $1.0
30 DATA exprodata<>+16(SB)/8, $2.0
31 DATA exprodata<>+24(SB)/8, $1.6666666666666666667e-1
32 DATA exprodata<>+32(SB)/8, $4.1666666666666666667e-2
33 DATA exprodata<>+40(SB)/8, $8.3333333333333333333e-3
34 DATA exprodata<>+48(SB)/8, $1.3888888888888888889e-3
35 DATA exprodata<>+56(SB)/8, $1.9841269841269841270e-4
36 DATA exprodata<>+64(SB)/8, $2.4801587301587301587e-5
37 GLOBL exprodata<>+0(SB), RODATA, $72
39 // func Exp(x float64) float64
40 TEXT ·archExp(SB),NOSPLIT,$0
41 // test bits for not-finite
43 MOVQ $~(1<<63), AX // sign bit mask
49 // check if argument will overflow
56 CVTSD2SL X1, BX // BX = exponent
68 // Taylor series evaluation
69 MOVSD exprodata<>+64(SB), X1
71 ADDSD exprodata<>+56(SB), X1
73 ADDSD exprodata<>+48(SB), X1
75 ADDSD exprodata<>+40(SB), X1
77 ADDSD exprodata<>+32(SB), X1
79 ADDSD exprodata<>+24(SB), X1
81 ADDSD exprodata<>+0(SB), X1
83 ADDSD exprodata<>+8(SB), X1
85 MOVSD exprodata<>+16(SB), X1
88 MOVSD exprodata<>+16(SB), X1
91 MOVSD exprodata<>+16(SB), X1
94 MOVSD exprodata<>+16(SB), X1
97 ADDSD exprodata<>+8(SB), X0
98 // return fr * 2**exponent
100 ADDL $0x3FF, BX // add bias
111 // test bits for -Inf
116 underflow: // return 0
119 overflow: // return +Inf
121 notNegInf: // NaN or +Inf, return x
127 ADDL $0x3FE, BX // add bias - 1
136 VFNMADD231SD X2, X1, X0
138 VFNMADD231SD X2, X1, X0
141 // Taylor series evaluation
142 MOVSD exprodata<>+64(SB), X1
143 VFMADD213SD exprodata<>+56(SB), X0, X1
144 VFMADD213SD exprodata<>+48(SB), X0, X1
145 VFMADD213SD exprodata<>+40(SB), X0, X1
146 VFMADD213SD exprodata<>+32(SB), X0, X1
147 VFMADD213SD exprodata<>+24(SB), X0, X1
148 VFMADD213SD exprodata<>+0(SB), X0, X1
149 VFMADD213SD exprodata<>+8(SB), X0, X1
151 VADDSD exprodata<>+16(SB), X0, X1
153 VADDSD exprodata<>+16(SB), X0, X1
155 VADDSD exprodata<>+16(SB), X0, X1
157 VADDSD exprodata<>+16(SB), X0, X1
158 VFMADD213SD exprodata<>+8(SB), X1, X0