[llvm-commits] CVS: llvm/include/llvm/DerivedTypes.h

[Reid Spencer]

Hi Chris,


On Sun, 2007-03-04 at 17:33 -0600, Chris Lattner wrote:
> 
> Changes in directory llvm/include/llvm:
> 
> DerivedTypes.h updated: 1.86 -> 1.87
> ---
> Log message:
> 
> add a getSignBit method, elimiante virtual method from getBitMask()
> 
> 
> ---
> Diffs of the changes:  (+7 -1)
> 
>  DerivedTypes.h |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletion(-)
> 
> 
> Index: llvm/include/llvm/DerivedTypes.h
> diff -u llvm/include/llvm/DerivedTypes.h:1.86 llvm/include/llvm/DerivedTypes.h:1.87
> --- llvm/include/llvm/DerivedTypes.h:1.86	Wed Feb 28 22:02:06 2007
> +++ llvm/include/llvm/DerivedTypes.h	Sun Mar  4 17:33:19 2007
> @@ -106,9 +106,15 @@
>    /// that can be set by an unsigned version of this type.  This is 0xFF for
>    /// sbyte/ubyte, 0xFFFF for shorts, etc.
>    uint64_t getBitMask() const {
> -    return ~uint64_t(0UL) >> (64-getPrimitiveSizeInBits());
> +    return ~uint64_t(0UL) >> (64-getBitWidth());
>    }
>  
> +  /// getSignBit - Return a uint64_t with just the most significant bit set (the
> +  /// sign bit, if the value is treated as a signed number).
> +  uint64_t getSignBit() const {
> +    return 1ULL << (getBitWidth()-1);
> +  }
> +  

I'm trying to get rid of such functions and you're adding more of
them :)

Please note that in many places (like the place you intend to use
getSignBit), it may be necessary to use APInt::getSignedMinValue() for
this value to enable it to work with > 64 bits. The exception to this is
GEP indexing which are known to be 32/64 bit indices. If your use is
similar, I suppose this is fine. If not, please note that when
InstructionCombining is done (Sheng's working on it), I intend to pass
through LLVM and get rid of calls to both of these functions, if
appropriate.

Reid.


>    /// For example, this is 0xFF for an 8 bit integer, 0xFFFF for i16, etc.
>    /// @returns a bit mask with ones set for all the bits of this type.
>    /// @brief Get a bit mask for this type.
> 
> 
> 
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits