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234 lines
6.9 KiB
ArmAsm
234 lines
6.9 KiB
ArmAsm
.file "roundf.s"
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// Copyright (c) 2000 - 2003, Intel Corporation
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// All rights reserved.
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//
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// Contributed 2000 by the Intel Numerics Group, Intel Corporation
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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//
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// * The name of Intel Corporation may not be used to endorse or promote
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// products derived from this software without specific prior written
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// permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS
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// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING
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// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// Intel Corporation is the author of this code, and requests that all
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// problem reports or change requests be submitted to it directly at
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// http://www.intel.com/software/products/opensource/libraries/num.htm.
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//
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// History
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//==============================================================
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// 10/25/00 Initial version
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// 06/14/01 Changed cmp to an equivalent form
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// 05/20/02 Cleaned up namespace and sf0 syntax
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// 01/20/03 Improved performance and reduced code size
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// 04/18/03 Eliminate possible WAW dependency warning
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// 09/03/03 Improved performance
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//==============================================================
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// API
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//==============================================================
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// float roundf(float x)
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//==============================================================
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// general input registers:
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// r14 - r18
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rSignexp = r14
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rExp = r15
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rExpMask = r16
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rBigexp = r17
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rExpHalf = r18
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// floating-point registers:
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// f8 - f13
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fXtruncInt = f9
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fNormX = f10
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fHalf = f11
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fInc = f12
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fRem = f13
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// predicate registers used:
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// p6 - p10
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// Overview of operation
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//==============================================================
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// float roundf(float x)
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// Return an integer value (represented as a float) that is x
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// rounded to nearest integer, halfway cases rounded away from
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// zero.
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// if x>0 result = trunc(x+0.5)
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// if x<0 result = trunc(x-0.5)
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//
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//==============================================================
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// double_extended
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// if the exponent is > 1003e => 3F(true) = 63(decimal)
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// we have a significand of 64 bits 1.63-bits.
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// If we multiply by 2^63, we no longer have a fractional part
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// So input is an integer value already.
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// double
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// if the exponent is >= 10033 => 34(true) = 52(decimal)
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// 34 + 3ff = 433
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// we have a significand of 53 bits 1.52-bits. (implicit 1)
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// If we multiply by 2^52, we no longer have a fractional part
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// So input is an integer value already.
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// single
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// if the exponent is > 10016 => 17(true) = 23(decimal)
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// we have a significand of 24 bits 1.23-bits. (implicit 1)
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// If we multiply by 2^23, we no longer have a fractional part
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// So input is an integer value already.
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.section .text
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GLOBAL_LIBM_ENTRY(roundf)
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{ .mfi
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getf.exp rSignexp = f8 // Get signexp, recompute if unorm
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fcvt.fx.trunc.s1 fXtruncInt = f8 // Convert to int in significand
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addl rBigexp = 0x10016, r0 // Set exponent at which is integer
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}
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{ .mfi
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mov rExpHalf = 0x0FFFE // Form sign and exponent of 0.5
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fnorm.s1 fNormX = f8 // Normalize input
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mov rExpMask = 0x1FFFF // Form exponent mask
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}
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;;
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{ .mfi
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setf.exp fHalf = rExpHalf // Form 0.5
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fclass.m p7,p0 = f8, 0x0b // Test x unorm
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nop.i 0
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}
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;;
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{ .mfb
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nop.m 0
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fclass.m p6,p0 = f8, 0x1e3 // Test x natval, nan, inf
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(p7) br.cond.spnt ROUND_UNORM // Branch if x unorm
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}
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;;
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ROUND_COMMON:
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// Return here from ROUND_UNORM
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{ .mfb
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nop.m 0
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fcmp.lt.s1 p8,p9 = f8, f0 // Test if x < 0
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(p6) br.cond.spnt ROUND_SPECIAL // Exit if x natval, nan, inf
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}
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;;
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{ .mfi
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nop.m 0
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fcvt.xf f8 = fXtruncInt // Pre-Result if 0.5 <= |x| < 2^23
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nop.i 0
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}
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;;
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{ .mfi
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and rExp = rSignexp, rExpMask // Get biased exponent
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fmerge.s fInc = fNormX, f1 // Form increment if |rem| >= 0.5
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nop.i 0
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}
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;;
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{ .mmi
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cmp.lt p6,p0 = rExp, rExpHalf // Is |x| < 0.5?
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cmp.ge p7,p0 = rExp, rBigexp // Is |x| >= 2^23?
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cmp.lt p10,p0 = rExp, rExpHalf // Is |x| < 0.5?
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}
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;;
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// We must correct result if |x| < 0.5, or |x| >= 2^23
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.pred.rel "mutex",p6,p7
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{ .mfi
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nop.m 0
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(p6) fmerge.s f8 = fNormX, f0 // If |x| < 0.5, result sgn(x)*0
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nop.i 0
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}
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{ .mfb
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(p7) cmp.eq p10,p0 = r0, r0 // Also turn on p10 if |x| >= 2^23
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(p7) fma.s.s0 f8 = fNormX, f1, f0 // If |x| >= 2^23, result x
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(p10) br.ret.spnt b0 // Exit |x| < 0.5 or |x| >= 2^23
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}
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;;
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// Here if 0.5 <= |x| < 2^23
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{ .mfi
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nop.m 0
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(p9) fms.s1 fRem = fNormX, f1, f8 // Get remainder = x - trunc(x)
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nop.i 0
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}
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{ .mfi
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nop.m 0
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(p8) fms.s1 fRem = f8, f1, fNormX // Get remainder = trunc(x) - x
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nop.i 0
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}
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;;
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{ .mfi
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nop.m 0
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fcmp.ge.s1 p9,p0 = fRem, fHalf // Test |rem| >= 0.5
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nop.i 0
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}
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;;
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// If x < 0 and remainder <= -0.5, then subtract 1 from result
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// If x > 0 and remainder >= +0.5, then add 1 to result
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{ .mfb
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nop.m 0
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(p9) fma.s.s0 f8 = f8, f1, fInc
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br.ret.sptk b0
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}
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;;
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ROUND_SPECIAL:
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// Here if x natval, nan, inf
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{ .mfb
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nop.m 0
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fma.s.s0 f8 = f8, f1, f0
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br.ret.sptk b0
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}
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;;
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ROUND_UNORM:
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// Here if x unorm
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{ .mfi
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getf.exp rSignexp = fNormX // Get signexp, recompute if unorm
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fcmp.eq.s0 p7,p0 = f8, f0 // Dummy op to set denormal flag
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nop.i 0
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}
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{ .mfb
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nop.m 0
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fcvt.fx.trunc.s1 fXtruncInt = fNormX // Convert to int in significand
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br.cond.sptk ROUND_COMMON // Return to main path
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}
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;;
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GLOBAL_LIBM_END(roundf)
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