github.com/MangoDowner/go-gm@v0.0.0-20180818020936-8baa2bd4408c/src/math/modf_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  #include "textflag.h"
     6  
     7  // func Modf(f float64) (int float64, frac float64)
     8  TEXT ·Modf(SB),NOSPLIT,$0
     9  	// special case for f == -0.0
    10  	MOVL f_hi+4(FP), DX	// high word
    11  	MOVL f_lo+0(FP), AX	// low word
    12  	CMPL DX, $(1<<31)	// beginning of -0.0
    13  	JNE notNegativeZero
    14  	CMPL AX, $0			// could be denormalized
    15  	JNE notNegativeZero
    16  	MOVL AX, int_lo+8(FP)
    17  	MOVL DX, int_hi+12(FP)
    18  	MOVL AX, frac_lo+16(FP)
    19  	MOVL DX, frac_hi+20(FP)
    20  	RET
    21  notNegativeZero:
    22  	FMOVD   f+0(FP), F0  // F0=f
    23  	FMOVD   F0, F1       // F0=f, F1=f
    24  	FSTCW   -2(SP)       // save old Control Word
    25  	MOVW    -2(SP), AX
    26  	ORW     $0x0c00, AX  // Rounding Control set to truncate
    27  	MOVW    AX, -4(SP)   // store new Control Word
    28  	FLDCW   -4(SP)       // load new Control Word
    29  	FRNDINT              // F0=trunc(f), F1=f
    30  	FLDCW   -2(SP)       // load old Control Word
    31  	FSUBD   F0, F1       // F0=trunc(f), F1=f-trunc(f)
    32  	FMOVDP  F0, int+8(FP)  // F0=f-trunc(f)
    33  	FMOVDP  F0, frac+16(FP)
    34  	RET