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Text file src/math/floor_amd64.s

Documentation: math

     1	// Copyright 2012 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	#define Big		0x4330000000000000 // 2**52
     8	
     9	// func Floor(x float64) float64
    10	TEXT ·Floor(SB),NOSPLIT,$0
    11		MOVQ	x+0(FP), AX
    12		MOVQ	$~(1<<63), DX // sign bit mask
    13		ANDQ	AX,DX // DX = |x|
    14		SUBQ	$1,DX
    15		MOVQ    $(Big - 1), CX // if |x| >= 2**52-1 or IsNaN(x) or |x| == 0, return x
    16		CMPQ	DX,CX
    17		JAE     isBig_floor
    18		MOVQ	AX, X0 // X0 = x
    19		CVTTSD2SQ	X0, AX
    20		CVTSQ2SD	AX, X1 // X1 = float(int(x))
    21		CMPSD	X1, X0, 1 // compare LT; X0 = 0xffffffffffffffff or 0
    22		MOVSD	$(-1.0), X2
    23		ANDPD	X2, X0 // if x < float(int(x)) {X0 = -1} else {X0 = 0}
    24		ADDSD	X1, X0
    25		MOVSD	X0, ret+8(FP)
    26		RET
    27	isBig_floor:
    28		MOVQ    AX, ret+8(FP) // return x
    29		RET
    30	
    31	// func Ceil(x float64) float64
    32	TEXT ·Ceil(SB),NOSPLIT,$0
    33		MOVQ	x+0(FP), AX
    34		MOVQ	$~(1<<63), DX // sign bit mask
    35		MOVQ	AX, BX // BX = copy of x
    36		ANDQ    DX, BX // BX = |x|
    37		MOVQ    $Big, CX // if |x| >= 2**52 or IsNaN(x), return x
    38		CMPQ    BX, CX
    39		JAE     isBig_ceil
    40		MOVQ	AX, X0 // X0 = x
    41		MOVQ	DX, X2 // X2 = sign bit mask
    42		CVTTSD2SQ	X0, AX
    43		ANDNPD	X0, X2 // X2 = sign
    44		CVTSQ2SD	AX, X1	// X1 = float(int(x))
    45		CMPSD	X1, X0, 2 // compare LE; X0 = 0xffffffffffffffff or 0
    46		ORPD	X2, X1 // if X1 = 0.0, incorporate sign
    47		MOVSD	$1.0, X3
    48		ANDNPD	X3, X0
    49		ORPD	X2, X0 // if float(int(x)) <= x {X0 = 1} else {X0 = -0}
    50		ADDSD	X1, X0
    51		MOVSD	X0, ret+8(FP)
    52		RET
    53	isBig_ceil:
    54		MOVQ	AX, ret+8(FP)
    55		RET
    56	
    57	// func Trunc(x float64) float64
    58	TEXT ·Trunc(SB),NOSPLIT,$0
    59		MOVQ	x+0(FP), AX
    60		MOVQ	$~(1<<63), DX // sign bit mask
    61		MOVQ	AX, BX // BX = copy of x
    62		ANDQ    DX, BX // BX = |x|
    63		MOVQ    $Big, CX // if |x| >= 2**52 or IsNaN(x), return x
    64		CMPQ    BX, CX
    65		JAE     isBig_trunc
    66		MOVQ	AX, X0
    67		MOVQ	DX, X2 // X2 = sign bit mask
    68		CVTTSD2SQ	X0, AX
    69		ANDNPD	X0, X2 // X2 = sign
    70		CVTSQ2SD	AX, X0 // X0 = float(int(x))
    71		ORPD	X2, X0 // if X0 = 0.0, incorporate sign
    72		MOVSD	X0, ret+8(FP)
    73		RET
    74	isBig_trunc:
    75		MOVQ    AX, ret+8(FP) // return x
    76		RET

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