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Help the compiler to eliminate some dead code when hashing an array of T

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where sizeof (T) is a multiple of 4.

llvm-svn: 151523
This commit is contained in:
Jay Foad 2012-02-27 11:00:17 +00:00
parent 7dc8ff6615
commit e019c92c2a
1 changed files with 5 additions and 3 deletions
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8
include/llvm/ADT/Hashing.h
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@ -142,6 +142,7 @@ private:
}
// Add a range of bytes from I to E.
template<bool ElementsHaveEvenLength>
void addBytes(const char *I, const char *E) {
uint32_t Data;
// Note that aliasing rules forbid us from dereferencing
@ -154,7 +155,7 @@ private:
std::memcpy(&Data, I, sizeof Data);
mix(Data);
}
if (I != E) {
if (!ElementsHaveEvenLength && I != E) {
Data = 0;
std::memcpy(&Data, I, E - I);
mix(Data);
@ -164,8 +165,9 @@ private:
// Add a range of bits from I to E.
template<typename T>
void addBits(const T *I, const T *E) {
addBytes(reinterpret_cast<const char *>(I),
reinterpret_cast<const char *>(E));
addBytes<sizeof (T) % sizeof (uint32_t) == 0>(
reinterpret_cast<const char *>(I),
reinterpret_cast<const char *>(E));
}
};