floor_amd64.s

     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 archFloor(x float64) float64
    10  TEXT ·archFloor(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 archCeil(x float64) float64
    32  TEXT ·archCeil(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 archTrunc(x float64) float64
    58  TEXT ·archTrunc(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
    77
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