[llvm] r302716 - [APInt] Add negate helper method to implement twos complement. Use it to shorten code.

[David Blaikie via llvm-commits]

On Wed, May 10, 2017 at 1:14 PM Craig Topper via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: ctopper
> Date: Wed May 10 15:01:38 2017
> New Revision: 302716
>
> URL: http://llvm.org/viewvc/llvm-project?rev=302716&view=rev
> Log:
> [APInt] Add negate helper method to implement twos complement. Use it to
> shorten code.
>
> Modified:
>     llvm/trunk/include/llvm/ADT/APInt.h
>     llvm/trunk/lib/Support/APInt.cpp
>
> Modified: llvm/trunk/include/llvm/ADT/APInt.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=302716&r1=302715&r2=302716&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/ADT/APInt.h (original)
> +++ llvm/trunk/include/llvm/ADT/APInt.h Wed May 10 15:01:38 2017
> @@ -1437,6 +1437,12 @@ public:
>    /// as "bitPosition".
>    void flipBit(unsigned bitPosition);
>
> +  /// Negate this APInt in place.
> +  void negate() {
> +    flipAllBits();
> +    ++(*this);
>

If you like, you can drop the () here ^ and write: ++*this


> +  }
> +
>    /// Insert the bits from a smaller APInt starting at bitPosition.
>    void insertBits(const APInt &SubBits, unsigned bitPosition);
>
> @@ -1996,8 +2002,7 @@ inline raw_ostream &operator<<(raw_ostre
>  }
>
>  inline APInt operator-(APInt v) {
> -  v.flipAllBits();
> -  ++v;
> +  v.negate();
>    return v;
>  }
>
>
> Modified: llvm/trunk/lib/Support/APInt.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=302716&r1=302715&r2=302716&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/APInt.cpp (original)
> +++ llvm/trunk/lib/Support/APInt.cpp Wed May 10 15:01:38 2017
> @@ -1846,10 +1846,8 @@ void APInt::fromString(unsigned numbits,
>      *this += digit;
>    }
>    // If its negative, put it in two's complement form
> -  if (isNeg) {
> -    --(*this);
> -    this->flipAllBits();
> -  }
> +  if (isNeg)
> +    this->negate();
>

Any particular reason for the "this->" qualification?


>  }
>
>  void APInt::toString(SmallVectorImpl<char> &Str, unsigned Radix,
> @@ -1927,8 +1925,7 @@ void APInt::toString(SmallVectorImpl<cha
>      // They want to print the signed version and it is a negative value
>      // Flip the bits and add one to turn it into the equivalent positive
>      // value and put a '-' in the result.
> -    Tmp.flipAllBits();
> -    ++Tmp;
> +    Tmp.negate();
>      Str.push_back('-');
>    }
>
>
>
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