1.file "nearbyintf.s"
2
3
4// Copyright (c) 2000 - 2003, Intel Corporation
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22
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38//
39// History
40//==============================================================
41// 10/19/00 Created
42// 02/08/01 Corrected behavior for all rounding modes.
43// 05/20/02 Cleaned up namespace and sf0 syntax
44// 02/10/03 Reordered header: .section, .global, .proc, .align
45// 07/25/03 Improved performance
46//==============================================================
47
48// API
49//==============================================================
50// float nearbyintf(float x)
51//==============================================================
52
53// general input registers:
54// r14 - r21
55
56rSignexp   = r14
57rExp       = r15
58rExpMask   = r16
59rBigexp    = r17
60rFpsr      = r19
61rRcs0      = r20
62rRcs0Mask  = r21
63
64// floating-point registers:
65// f8 - f10
66
67fXInt      = f9
68fNormX     = f10
69
70// predicate registers used:
71// p6 - p10
72
73// Overview of operation
74//==============================================================
75// float nearbyintf(float x)
76// Return an integer value (represented as a float) that is x
77// rounded to integer in current rounding mode
78// Inexact is not set, otherwise result identical with rint.
79//==============================================================
80
81// double_extended
82// if the exponent is > 1003e => 3F(true) = 63(decimal)
83// we have a significand of 64 bits 1.63-bits.
84// If we multiply by 2^63, we no longer have a fractional part
85// So input is an integer value already.
86
87// double
88// if the exponent is >= 10033 => 34(true) = 52(decimal)
89// 34 + 3ff = 433
90// we have a significand of 53 bits 1.52-bits. (implicit 1)
91// If we multiply by 2^52, we no longer have a fractional part
92// So input is an integer value already.
93
94// single
95// if the exponent is > 10016 => 17(true) = 23(decimal)
96// we have a significand of 24 bits 1.23-bits. (implicit 1)
97// If we multiply by 2^23, we no longer have a fractional part
98// So input is an integer value already.
99
100.section .text
101GLOBAL_LIBM_ENTRY(nearbyintf)
102
103{ .mfi
104      getf.exp         rSignexp  = f8        // Get signexp, recompute if unorm
105      fclass.m         p7,p0 = f8, 0x0b      // Test x unorm
106      addl             rBigexp = 0x10016, r0 // Set exponent at which is integer
107}
108{ .mfi
109      nop.m            0
110      fcvt.fx.s1       fXInt  = f8           // Convert to int in significand
111      mov              rExpMask    = 0x1FFFF // Form exponent mask
112}
113;;
114
115{ .mfi
116      mov              rFpsr = ar40          // Read fpsr -- check rc.s0
117      fclass.m         p6,p0 = f8, 0x1e3     // Test x natval, nan, inf
118      nop.i            0
119}
120{ .mfb
121      nop.m            0
122      fnorm.s1         fNormX  = f8          // Normalize input
123(p7)  br.cond.spnt     RINT_UNORM            // Branch if x unorm
124}
125;;
126
127
128RINT_COMMON:
129// Return here from RINT_UNORM
130{ .mfb
131      and              rExp = rSignexp, rExpMask // Get biased exponent
132(p6)  fma.s.s0         f8 = f8, f1, f0       // Result if x natval, nan, inf
133(p6)  br.ret.spnt      b0                    // Exit if x natval, nan, inf
134}
135;;
136
137{ .mfi
138      mov              rRcs0Mask = 0x0c00     // Mask for rc.s0
139      fcvt.xf          f8 = fXInt             // Result assume |x| < 2^23
140      cmp.ge           p7,p8 = rExp, rBigexp  // Is |x| >= 2^23?
141}
142;;
143
144// We must correct result if |x| >= 2^23
145{ .mfi
146      nop.m            0
147(p7)  fma.s.s0         f8 = fNormX, f1, f0    // If |x| >= 2^23, result x
148      nop.i            0
149}
150;;
151
152{ .mfi
153      nop.m            0
154(p8)  fmerge.s         f8 = fNormX, f8        // Make sign nearbyintf(x)= sign x
155      nop.i            0
156}
157;;
158
159{ .mfi
160(p8)  and              rRcs0 = rFpsr, rRcs0Mask // Get rounding mode for sf0
161      nop.f            0
162      nop.i            0
163}
164;;
165
166// If |x| < 2^23 we must test for other rounding modes
167{ .mbb
168(p8)  cmp.ne.unc       p10,p0 = rRcs0, r0     // Test for other rounding modes
169(p10) br.cond.spnt     RINT_NOT_ROUND_NEAREST // Branch if not round nearest
170      br.ret.sptk      b0                     // Exit main path if round nearest
171}
172;;
173
174
175RINT_UNORM:
176// Here if x unorm
177{ .mfb
178      getf.exp         rSignexp  = fNormX     // Get signexp, recompute if unorm
179      fcmp.eq.s0       p7,p0 = f8, f0         // Dummy op to set denormal flag
180      br.cond.sptk     RINT_COMMON            // Return to main path
181}
182;;
183
184RINT_NOT_ROUND_NEAREST:
185// Here if not round to nearest, and |x| < 2^23
186// Set rounding mode of s2 to that of s0, and repeat the conversion using s2
187{ .mfi
188      nop.m            0
189      fsetc.s2         0x7f, 0x40
190      nop.i            0
191}
192;;
193
194{ .mfi
195      nop.m            0
196      fcvt.fx.s2       fXInt  = fNormX        // Convert to int in significand
197      nop.i            0
198}
199;;
200
201{ .mfi
202      nop.m            0
203      fcvt.xf          f8 = fXInt             // Expected result
204      nop.i            0
205}
206;;
207
208// Be sure sign of result = sign of input.  Fixes cases where result is 0.
209{ .mfb
210      nop.m            0
211      fmerge.s         f8 = fNormX, f8
212      br.ret.sptk      b0                     // Exit main path
213}
214;;
215
216GLOBAL_LIBM_END(nearbyintf)
217libm_alias_float_other (nearbyint, nearbyint)
218