3402aac7d9
Trailing spaces create issue/warning when generating/applying patches. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ronald Cron <ronald.cron@arm.com> Reviewed-By: Olivier Martin <olivier.martin@arm.com> git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15833 6f19259b-4bc3-4df7-8a09-765794883524
97 lines
3.4 KiB
C
97 lines
3.4 KiB
C
/** @file
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Compiler intrinsic to return the number of leading zeros, ported from LLVM code.
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Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
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This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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/**
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University of Illinois/NCSA
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Open Source License
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Copyright (c) 2003-2008 University of Illinois at Urbana-Champaign.
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All rights reserved.
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Developed by:
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LLVM Team
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University of Illinois at Urbana-Champaign
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http://llvm.org
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal with
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do
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so, subject to the following conditions:
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* Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimers.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimers in the
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documentation and/or other materials provided with the distribution.
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* Neither the names of the LLVM Team, University of Illinois at
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Urbana-Champaign, nor the names of its contributors may be used to
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endorse or promote products derived from this Software without specific
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prior written permission.
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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, FITNESS
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FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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CONTRIBUTORS 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 FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
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SOFTWARE.
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**/
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#include "Llvm_int_lib.h"
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// Returns: the number of leading 0-bits
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// Precondition: a != 0
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INT32
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__clzsi2(INT32 a)
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{
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UINT32 x = (UINT32)a;
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INT32 t = ((x & 0xFFFF0000) == 0) << 4; // if (x is small) t = 16 else 0
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x >>= 16 - t; // x = [0 - 0xFFFF]
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UINT32 r = t; // r = [0, 16]
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// return r + clz(x)
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t = ((x & 0xFF00) == 0) << 3;
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x >>= 8 - t; // x = [0 - 0xFF]
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r += t; // r = [0, 8, 16, 24]
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// return r + clz(x)
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t = ((x & 0xF0) == 0) << 2;
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x >>= 4 - t; // x = [0 - 0xF]
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r += t; // r = [0, 4, 8, 12, 16, 20, 24, 28]
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// return r + clz(x)
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t = ((x & 0xC) == 0) << 1;
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x >>= 2 - t; // x = [0 - 3]
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r += t; // r = [0 - 30] and is even
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// return r + clz(x)
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// switch (x)
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// {
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// case 0:
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// return r + 2;
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// case 1:
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// return r + 1;
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// case 2:
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// case 3:
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// return r;
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// }
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return r + ((2 - x) & -((x & 2) == 0));
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}
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