[llvm-commits] CVS: llvm/lib/Transforms/Scalar/InstructionCombining.cpp

[Chris Lattner]

>>> Make some codes more efficient.
>>>
>>> @@ -5813,7 +5816,6 @@
>>>        case 16 : SExtType = Type::Int16Ty; break;
>>>        case 32 : SExtType = Type::Int32Ty; break;
>>>        case 64 : SExtType = Type::Int64Ty; break;
>>> -      case 128: SExtType = IntegerType::get(128); break;
>>>        default: break;
>>>        }
>>>        if (SExtType) {
>>
>> why did you remove this?
>
> I asked Sheng to remove it because the back ends cannot deal with 128
> bit integers.

There is partial support already in place, and at some point, it  
should be extended.  See, for example:
CodeGen/Generic/i128-arith.ll

which works on all targets with the native codegen.

>>> @@ -5833,7 +5835,7 @@
>>>            BinaryOperator::createShl(X, ConstantInt::get(Ty,
>>> ShiftDiff));
>>>          InsertNewInstBefore(Shift, I);
>>>
>>> -        APInt Mask(APInt::getAllOnesValue(TypeBits).shl 
>>> (ShiftAmt2));
>>> +        APInt Mask(Ty->getMask().shl(ShiftAmt2));
>>
>> You touched many instances of this.  Please make a new
>> APInt::getHighBits method.
>
> The method getHiBits already exists and is used to extrat the N hi  
> bits
> from an existing APInt, not construct a new value. I have just  
> committed
> a re-organization of the APInt interface (mostly for documentation
> purposes) but while I was at it I added three new functions that  
> should
> address this need:

Nice.

-Chris
>
>   /// Constructs an APInt value that has a contiguous range of bits  
> set.
> The
>   /// bits from loBit to hiBit will be set. All other bits will be  
> zero.
> For
>   /// example, with parameters(32, 15, 0) you would get 0x0000FFFF. If
> hiBit is
>   /// less than loBit then the set bits "wrap". For example, with
>   /// parameters (32, 3, 28), you would get 0xF000000F.
>   /// @param numBits the intended bit width of the result
>   /// @param hiBit the index of the highest bit set.
>   /// @param loBit the index of the lowest bit set.
>   /// @returns An APInt value with the requested bits set.
>   /// @brief Get a value with a block of bits set.
>   static APInt getBitsSet(uint32_t numBits, uint32_t hiBit, uint32_t
> loBit = 0);
>
>   /// Constructs an APInt value that has the top hiBitsSet bits set.
>   /// @param numBits the bitwidth of the result
>   /// @param hiBitsSet the number of high-order bits set in the  
> result.
>   /// @brief Get a value with high bits set
>   static APInt getHighBitsSet(uint32_t numBits, uint32_t hiBitsSet);
>
>   /// Constructs an APInt value that has the bottom loBitsSet bits  
> set.
>   /// @param numBits the bitwidth of the result
>   /// @param loBitsSet the number of low-order bits set in the result.
>   /// @brief Get a value with low bits set
>   static APInt getLowBitsSet(uint32_t numBits, uint32_t loBitsSet);
>
> Reid.
>
>>
>> -Chris
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>