[LLVMdev] question on code in PointerIntPair.h

[Maurizio Vitale]

>>>>> "Chris" == Chris Lattner <clattner at apple.com> writes:

    Chris> On Oct 8, 2009, at 10:50 AM, Maurizio Vitale wrote:

> around line 45 a bitmask is computed as:
    >> 
    >> PointerBitMask = ~(uintptr_t)(((intptr_t)1 <<
    >> PtrTraits::NumLowBitsAvailable)-1),
    >> 
    >> my question is why is the shift performed on intptr_t? Wouldn't
    >> the following be ok?
    >> 
    >> PointerBitMask = ~(((uintptr_t)1 <<
    >> PtrTraits::NumLowBitsAvailable)-1),

    Chris> Hi Maurizio, why do you ask?  Is the existing code causing a
    Chris> problem?

Not at all (I'm not really a llvm/clang user yet, only an interested
observer).

The reason is that this particular file has been mentioned on the boost
developer mailing list in a thread on compressed pointers/integer
pairs. 

I'm working on bringing some code of mine up to boost standards for a
review and I was tracking down all things in that thread.

I noticed thatyou were doing things differently from me and I was
wandering if there was a reason that I couldn't see.

Are you aware of a reason?

TIA,
        
        Maurizio
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