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. 4 5 #include "textflag.h" 6 7 // func Log1p(x float64) float64 8 TEXT Log1p(SB),NOSPLIT,$0 9 FMOVD $(2.928932188134524e-01), F0 10 FMOVD x+0(FP), F0 // F0=x, F1=1-sqrt(2)/2 = 0.29289321881345247559915564 11 FABS // F0=|x|, F1=1-sqrt(2)/2 12 FUCOMPP F0, F1 // compare F0 to F1 13 FSTSW AX 14 FLDLN2 // F0=log(2) 15 ANDW $0x0100, AX 16 JEQ use_fyl2x // jump if F0 >= F1 17 FMOVD x+0(FP), F0 // F0=x, F1=log(2) 18 FYL2XP1 // F0=log(1+x)=log2(1+x)*log(2) 19 FMOVDP F0, ret+8(FP) 20 RET 21 use_fyl2x: 22 FLD1 // F0=1, F2=log(2) 23 FADDD x+0(FP), F0 // F0=1+x, F1=log(2) 24 FYL2X // F0=log(1+x)=log2(1+x)*log(2) 25 FMOVDP F0, ret+8(FP) 26 RET 27 28
