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.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)
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