github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/math/log1p_386.s (about)

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