Matt Turner
036e347f3c
The SSE 4.1 ROUND instructions let us implement roundeven directly. Otherwise we assume that the rounding mode has not been modified (as we do in the rest of Mesa) and use rint(). glibc uses the ROUND instruction in rint() after a cpuid check. This patch just lets us inline it directly when we're already building for SSE 4.1. Reviewed-by: Carl Worth <cworth@cworth.org>
79 lines
2.6 KiB
C
79 lines
2.6 KiB
C
/*
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* Copyright © 2015 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include <math.h>
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#ifdef __SSE4_1__
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#include <smmintrin.h>
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#endif
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/* The C standard library has functions round()/rint()/nearbyint() that round
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* their arguments according to the rounding mode set in the floating-point
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* control register. While there are trunc()/ceil()/floor() functions that do
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* a specific operation without modifying the rounding mode, there is no
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* roundeven() in any version of C.
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*
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* Technical Specification 18661 (ISO/IEC TS 18661-1:2014) adds roundeven(),
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* but it's unfortunately not implemented by glibc.
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*
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* This implementation differs in that it does not raise the inexact exception.
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*
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* We use rint() to implement these functions, with the assumption that the
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* floating-point rounding mode has not been changed from the default Round
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* to Nearest.
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*/
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/**
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* \brief Rounds \c x to the nearest integer, with ties to the even integer.
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*/
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static inline float
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_mesa_roundevenf(float x)
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{
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#ifdef __SSE4_1__
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float ret;
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__m128 m = _mm_load_ss(&x);
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m = _mm_round_ss(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
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_mm_store_ss(&ret, m);
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return ret;
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#else
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return rintf(x);
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#endif
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}
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/**
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* \brief Rounds \c x to the nearest integer, with ties to the even integer.
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*/
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static inline double
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_mesa_roundeven(double x)
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{
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#ifdef __SSE4_1__
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double ret;
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__m128d m = _mm_load_sd(&x);
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m = _mm_round_sd(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
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_mm_store_sd(&ret, m);
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return ret;
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#else
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return rint(x);
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#endif
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}
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