llvm dev - Jun 2011 - [LLVMdev] Bug in FoldingSetNodeID::AddInteger(unsigned long long I)?

The current implementation is:


void FoldingSetNodeID::AddInteger(unsigned long long I) {
  AddInteger(unsigned(I));
  if ((uint64_t)(int)I != I)
    Bits.push_back(unsigned(I >> 32));
}
 
(uint64_t)(int)I first truncates I to signed int, which causes the second cast
to sign extend the value to 64 bits. The problem is that if the 31st bit of the
original value is 1, the sign extended value would be different than the
original one even if the high 32 bits of the original value are all 0. This may
contradict the original intention of this code.


Should the correct implementation be:  if ((uint64_t)(unsigned)I != I) ?
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