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Aligned and unaligned copies of the same string

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were not hashing to the same value.  Analysis
and patch by Frits van Bommel!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119770 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2010-11-19 00:48:58 +00:00
parent cb21d1c9fd
commit c81c7fe643
1 changed files with 22 additions and 7 deletions
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29
lib/Support/FoldingSet.cpp
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@ -18,6 +18,7 @@
#include "llvm/Support/Allocator.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/System/Host.h"
#include <cassert>
#include <cstring>
using namespace llvm;
@ -110,18 +111,32 @@ void FoldingSetNodeID::AddString(StringRef String) {
Pos = (Units + 1) * 4;
} else {
// Otherwise do it the hard way.
for (Pos += 4; Pos <= Size; Pos += 4) {
unsigned V = ((unsigned char)String[Pos - 4] << 24) |
((unsigned char)String[Pos - 3] << 16) |
((unsigned char)String[Pos - 2] << 8) |
(unsigned char)String[Pos - 1];
Bits.push_back(V);
// To be compatible with above bulk transfer, we need to take endianness
// into account.
if (sys::isBigEndianHost()) {
for (Pos += 4; Pos <= Size; Pos += 4) {
unsigned V = ((unsigned char)String[Pos - 4] << 24) |
((unsigned char)String[Pos - 3] << 16) |
((unsigned char)String[Pos - 2] << 8) |
(unsigned char)String[Pos - 1];
Bits.push_back(V);
}
} else {
assert(sys::isLittleEndianHost() && "Unexpected host endianness");
for (Pos += 4; Pos <= Size; Pos += 4) {
unsigned V = ((unsigned char)String[Pos - 1] << 24) |
((unsigned char)String[Pos - 2] << 16) |
((unsigned char)String[Pos - 3] << 8) |
(unsigned char)String[Pos - 4];
Bits.push_back(V);
}
}
}
// With the leftover bits.
unsigned V = 0;
// Pos will have overshot size by 4 - #bytes left over.
// Pos will have overshot size by 4 - #bytes left over.
// No need to take endianness into account here - this is always executed.
switch (Pos - Size) {
case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.