root/src/pkg/math/modf_386.s

// 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 "../../cmd/ld/textflag.h"

// func Modf(f float64) (int float64, frac float64)
TEXT ·Modf(SB),NOSPLIT,$0
        FMOVD   f+0(FP), F0  // F0=f
        FMOVD   F0, F1       // F0=f, F1=f
        FSTCW   -2(SP)       // save old Control Word
        MOVW    -2(SP), AX
        ORW     $0x0c00, AX  // Rounding Control set to truncate
        MOVW    AX, -4(SP)   // store new Control Word
        FLDCW   -4(SP)       // load new Control Word
        FRNDINT              // F0=trunc(f), F1=f
        FLDCW   -2(SP)       // load old Control Word
        FSUBD   F0, F1       // F0=trunc(f), F1=f-trunc(f)
        FMOVDP  F0, int+8(FP)  // F0=f-trunc(f)
        FMOVDP  F0, frac+16(FP)
        RET