| // Copyright 2010 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| #include "textflag.h" | |
| // func Log1p(x float64) float64 | |
| TEXT ·Log1p(SB),NOSPLIT,$0 | |
| FMOVD $(2.928932188134524e-01), F0 | |
| FMOVD x+0(FP), F0 // F0=x, F1=1-sqrt(2)/2 = 0.29289321881345247559915564 | |
| FABS // F0=|x|, F1=1-sqrt(2)/2 | |
| FUCOMPP F0, F1 // compare F0 to F1 | |
| FSTSW AX | |
| FLDLN2 // F0=log(2) | |
| ANDW $0x0100, AX | |
| JEQ use_fyl2x // jump if F0 >= F1 | |
| FMOVD x+0(FP), F0 // F0=x, F1=log(2) | |
| FYL2XP1 // F0=log(1+x)=log2(1+x)*log(2) | |
| FMOVDP F0, ret+8(FP) | |
| RET | |
| use_fyl2x: | |
| FLD1 // F0=1, F2=log(2) | |
| FADDD x+0(FP), F0 // F0=1+x, F1=log(2) | |
| FYL2X // F0=log(1+x)=log2(1+x)*log(2) | |
| FMOVDP F0, ret+8(FP) | |
| RET | |