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40 //==============================================================
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 //==============================================================
49 //==============================================================
50 // double nearbyint(double x)
51 //==============================================================
53 // general input registers:
64 // floating-point registers:
70 // predicate registers used:
73 // Overview of operation
74 //==============================================================
75 // double nearbyint(double x)
76 // Return an integer value (represented as a double) that is x
77 // rounded to integer in current rounding mode
78 // Inexact is not set, otherwise result identical with rint.
79 //==============================================================
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.
88 // if the exponent is >= 10033 => 34(true) = 52(decimal)
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.
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.
101 GLOBAL_LIBM_ENTRY(nearbyint)
104 getf.exp rSignexp = f8 // Get signexp, recompute if unorm
105 fclass.m p7,p0 = f8, 0x0b // Test x unorm
106 addl rBigexp = 0x10033, r0 // Set exponent at which is integer
110 fcvt.fx.s1 fXInt = f8 // Convert to int in significand
111 mov rExpMask = 0x1FFFF // Form exponent mask
116 mov rFpsr = ar40 // Read fpsr -- check rc.s0
117 fclass.m p6,p0 = f8, 0x1e3 // Test x natval, nan, inf
122 fnorm.s1 fNormX = f8 // Normalize input
123 (p7) br.cond.spnt RINT_UNORM // Branch if x unorm
129 // Return here from RINT_UNORM
131 and rExp = rSignexp, rExpMask // Get biased exponent
132 (p6) fma.d.s0 f8 = f8, f1, f0 // Result if x natval, nan, inf
133 (p6) br.ret.spnt b0 // Exit if x natval, nan, inf
138 mov rRcs0Mask = 0x0c00 // Mask for rc.s0
139 fcvt.xf f8 = fXInt // Result assume |x| < 2^52
140 cmp.ge p7,p8 = rExp, rBigexp // Is |x| >= 2^52?
144 // We must correct result if |x| >= 2^52
147 (p7) fma.d.s0 f8 = fNormX, f1, f0 // If |x| >= 2^52, result x
154 (p8) fmerge.s f8 = fNormX, f8 // Make sign nearbyint(x) = sign x
160 (p8) and rRcs0 = rFpsr, rRcs0Mask // Get rounding mode for sf0
166 // If |x| < 2^52 we must test for other rounding modes
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
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
184 RINT_NOT_ROUND_NEAREST:
185 // Here if not round to nearest, and |x| < 2^52
186 // Set rounding mode of s2 to that of s0, and repeat the conversion using s2
196 fcvt.fx.s2 fXInt = fNormX // Convert to int in significand
203 fcvt.xf f8 = fXInt // Expected result
208 // Be sure sign of result = sign of input. Fixes cases where result is 0.
211 fmerge.s f8 = fNormX, f8
212 br.ret.sptk b0 // Exit main path
216 GLOBAL_LIBM_END(nearbyint)
217 libm_alias_double_other (nearbyint, nearbyint)