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a7c01e7a53
COFF sections are accompanied with an auxiliary symbol which includes a checksum. This checksum used to be filled with just zero but this seems to upset LINK.exe when it is processing a /INCREMENTAL link job. Instead, fill the CheckSum field with the JamCRC of the section contents. This matches MSVC's behavior. This fixes PR19666. N.B. A rather simple implementation of JamCRC is given. It implements a byte-wise calculation using the method given by Sarwate. There are implementations with higher throughput like slice-by-eight and making use of PCLMULQDQ. We can switch to one of those techniques if it turns out to be a significant use of time. llvm-svn: 246590
49 lines
1.3 KiB
C++
49 lines
1.3 KiB
C++
//===-- llvm/Support/JamCRC.h - Cyclic Redundancy Check ---------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains an implementation of JamCRC.
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//
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// We will use the "Rocksoft^tm Model CRC Algorithm" to describe the properties
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// of this CRC:
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// Width : 32
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// Poly : 04C11DB7
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// Init : FFFFFFFF
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// RefIn : True
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// RefOut : True
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// XorOut : 00000000
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// Check : 340BC6D9 (result of CRC for "123456789")
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//
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// N.B. We permit flexibility of the "Init" value. Some consumers of this need
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// it to be zero.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_JAMCRC_H
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#define LLVM_SUPPORT_JAMCRC_H
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/Support/DataTypes.h"
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namespace llvm {
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class JamCRC {
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public:
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JamCRC(uint32_t Init = 0xFFFFFFFFU) : CRC(Init) {}
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// \brief Update the CRC calculation with Data.
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void update(ArrayRef<char> Data);
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uint32_t getCRC() const { return CRC; }
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private:
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uint32_t CRC;
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};
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} // End of namespace llvm
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#endif
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