about summary refs log tree commit diff
path: root/sysdeps/ia64/fpu/s_nearbyint.S
blob: ec1ff22dbc9d4ac0758db8c55767750db1a67bd1 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
.file "nearbyint.s"


// Copyright (c) 2000 - 2003, Intel Corporation
// All rights reserved.
//
// Contributed 2000 by the Intel Numerics Group, Intel Corporation
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// * The name of Intel Corporation may not be used to endorse or promote
// products derived from this software without specific prior written
// permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Intel Corporation is the author of this code, and requests that all
// problem reports or change requests be submitted to it directly at
// http://www.intel.com/software/products/opensource/libraries/num.htm.
//
// History
//==============================================================
// 10/19/00 Created
// 02/08/01 Corrected behavior for all rounding modes.
// 05/20/02 Cleaned up namespace and sf0 syntax
// 02/10/03 Reordered header: .section, .global, .proc, .align
// 07/25/03 Improved performance
//==============================================================

// API
//==============================================================
// double nearbyint(double x)
//==============================================================

// general input registers:
// r14 - r21

rSignexp   = r14
rExp       = r15
rExpMask   = r16
rBigexp    = r17
rFpsr      = r19
rRcs0      = r20
rRcs0Mask  = r21

// floating-point registers:
// f8 - f10

fXInt      = f9
fNormX     = f10

// predicate registers used:
// p6 - p10

// Overview of operation
//==============================================================
// double nearbyint(double x)
// Return an integer value (represented as a double) that is x
// rounded to integer in current rounding mode
// Inexact is not set, otherwise result identical with rint.
//==============================================================

// double_extended
// if the exponent is > 1003e => 3F(true) = 63(decimal)
// we have a significand of 64 bits 1.63-bits.
// If we multiply by 2^63, we no longer have a fractional part
// So input is an integer value already.

// double
// if the exponent is >= 10033 => 34(true) = 52(decimal)
// 34 + 3ff = 433
// we have a significand of 53 bits 1.52-bits. (implicit 1)
// If we multiply by 2^52, we no longer have a fractional part
// So input is an integer value already.

// single
// if the exponent is > 10016 => 17(true) = 23(decimal)
// we have a significand of 24 bits 1.23-bits. (implicit 1)
// If we multiply by 2^23, we no longer have a fractional part
// So input is an integer value already.

.section .text
GLOBAL_LIBM_ENTRY(nearbyint)

{ .mfi
      getf.exp         rSignexp  = f8        // Get signexp, recompute if unorm
      fclass.m         p7,p0 = f8, 0x0b      // Test x unorm
      addl             rBigexp = 0x10033, r0 // Set exponent at which is integer
}
{ .mfi
      nop.m            0
      fcvt.fx.s1       fXInt  = f8           // Convert to int in significand
      mov              rExpMask    = 0x1FFFF // Form exponent mask
}
;;

{ .mfi
      mov              rFpsr = ar40          // Read fpsr -- check rc.s0
      fclass.m         p6,p0 = f8, 0x1e3     // Test x natval, nan, inf
      nop.i            0
}
{ .mfb
      nop.m            0
      fnorm.s1         fNormX  = f8          // Normalize input
(p7)  br.cond.spnt     RINT_UNORM            // Branch if x unorm
}
;;


RINT_COMMON:
// Return here from RINT_UNORM
{ .mfb
      and              rExp = rSignexp, rExpMask // Get biased exponent
(p6)  fma.d.s0         f8 = f8, f1, f0       // Result if x natval, nan, inf
(p6)  br.ret.spnt      b0                    // Exit if x natval, nan, inf
}
;;

{ .mfi
      mov              rRcs0Mask = 0x0c00     // Mask for rc.s0
      fcvt.xf          f8 = fXInt             // Result assume |x| < 2^52
      cmp.ge           p7,p8 = rExp, rBigexp  // Is |x| >= 2^52?
}
;;

// We must correct result if |x| >= 2^52
{ .mfi
      nop.m            0
(p7)  fma.d.s0         f8 = fNormX, f1, f0    // If |x| >= 2^52, result x
      nop.i            0
}
;;

{ .mfi
      nop.m            0
(p8)  fmerge.s         f8 = fNormX, f8        // Make sign nearbyint(x) = sign x
      nop.i            0
}
;;

{ .mfi
(p8)  and              rRcs0 = rFpsr, rRcs0Mask // Get rounding mode for sf0
      nop.f            0
      nop.i            0
}
;;

// If |x| < 2^52 we must test for other rounding modes
{ .mbb
(p8)  cmp.ne.unc       p10,p0 = rRcs0, r0     // Test for other rounding modes
(p10) br.cond.spnt     RINT_NOT_ROUND_NEAREST // Branch if not round nearest
      br.ret.sptk      b0                     // Exit main path if round nearest
}
;;


RINT_UNORM:
// Here if x unorm
{ .mfb
      getf.exp         rSignexp  = fNormX     // Get signexp, recompute if unorm
      fcmp.eq.s0       p7,p0 = f8, f0         // Dummy op to set denormal flag
      br.cond.sptk     RINT_COMMON            // Return to main path
}
;;

RINT_NOT_ROUND_NEAREST:
// Here if not round to nearest, and |x| < 2^52
// Set rounding mode of s2 to that of s0, and repeat the conversion using s2
{ .mfi
      nop.m            0
      fsetc.s2         0x7f, 0x40
      nop.i            0
}
;;

{ .mfi
      nop.m            0
      fcvt.fx.s2       fXInt  = fNormX        // Convert to int in significand
      nop.i            0
}
;;

{ .mfi
      nop.m            0
      fcvt.xf          f8 = fXInt             // Expected result
      nop.i            0
}
;;

// Be sure sign of result = sign of input.  Fixes cases where result is 0.
{ .mfb
      nop.m            0
      fmerge.s         f8 = fNormX, f8
      br.ret.sptk      b0                     // Exit main path
}
;;

GLOBAL_LIBM_END(nearbyint)