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The implementation of GeneralHash::addBits broke C++ aliasing rules; fix

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it with memcpy. This also fixes a problem on big-endian hosts, where
addUnaligned would return different results depending on the alignment
of the data.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151247 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jay Foad
2012-02-23 09:16:04 +00:00
parent 9d91c5d31c
commit 6592eacf90
2 changed files with 20 additions and 72 deletions
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46
lib/Support/Hashing.cpp
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@@ -1,46 +0,0 @@
//===-- llvm/ADT/Hashing.cpp - Utilities for hashing ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/Hashing.h"
namespace llvm {
// Add a possibly unaligned sequence of bytes.
void GeneralHash::addUnaligned(const uint8_t *I, const uint8_t *E) {
ptrdiff_t Length = E - I;
if ((uintptr_t(I) & 3) == 0) {
while (Length > 3) {
mix(*reinterpret_cast<const uint32_t *>(I));
I += 4;
Length -= 4;
}
} else {
while (Length > 3) {
mix(
uint32_t(I[0]) +
(uint32_t(I[1]) << 8) +
(uint32_t(I[2]) << 16) +
(uint32_t(I[3]) << 24));
I += 4;
Length -= 4;
}
}
if (Length & 3) {
uint32_t Data = 0;
switch (Length & 3) {
case 3: Data |= uint32_t(I[2]) << 16; // fall through
case 2: Data |= uint32_t(I[1]) << 8; // fall through
case 1: Data |= uint32_t(I[0]); break;
}
mix(Data);
}
}
}