[llvm-commits] [llvm] r85814 - /llvm/trunk/lib/Analysis/MemoryBuiltins.cpp

[Victor Hernandez]

Fixed these in r85933.

Victor

On Nov 2, 2009, at 8:29 PM, Chris Lattner wrote:

> On Nov 2, 2009, at 10:51 AM, Victor Hernandez wrote:
>> URL: http://llvm.org/viewvc/llvm-project?rev=85814&view=rev
>> Log:
>> Set bit instead of calling pow() to compute 2 << n
>
> Thanks Victor,
>
>> +++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Mon Nov  2 12:51:28  
>> 2009
>> @@ -16,6 +16,7 @@
>> #include "llvm/Constants.h"
>> #include "llvm/Instructions.h"
>> #include "llvm/Module.h"
>> +#include "llvm/ADT/APInt.h"
>
> You don't need this #include, please remove it.
>
>> @@ -156,15 +157,22 @@
>>        return Op1;
>>    }
>>    if (Opcode == Instruction::Shl) {
>> -      ConstantInt* Op1Int = dyn_cast<ConstantInt>(Op1);
>> -      if (!Op1Int) return NULL;
>> -      Value* Op1Pow = ConstantInt::get(Op1->getType(), (uint64_t)
>> -                                    pow(2.0, (double) Op1Int- 
>> >getZExtValue()));
>> +      ConstantInt* Op1CI = dyn_cast<ConstantInt>(Op1);
>> +      if (!Op1CI) return NULL;
>> +
>> +      APInt Op1Int = Op1CI->getValue();
>> +      unsigned Op1Width = Op1Int.getBitWidth();
>> +      // check for overflow
>> +      if (Op1Int.getActiveBits() > 64 || Op1Int.getZExtValue() >  
>> Op1Width)
>> +        return NULL;
>
> If the shift overflows, the original code is undefined.  Please just  
> use the APInt::getLimitedValue method  (with the bitwidth as the  
> argument) to handle this.  You'll end up with much more elegant code.
>
> Finally, please use:
>
>  ConstantInt *Op1CI
> instead of:
>  ConstantInt* Op1CI
>
> With Op1CI and many other variables in this file.
>
> Thanks,
>
> -Chris
>
>
>
>> +      Value* Op1Pow = ConstantInt::get(Context,
>> +                                 APInt(Op1Width, 0).set 
>> (Op1Int.getZExtValue()));
>> +
>>      if (Op0 == ElementSize || (FoldedElementSize && Op0 ==  
>> FoldedElementSize))
>>        // ArraySize << log2(ElementSize)
>>        return Op1Pow;
>>      if (Op1Pow == ElementSize ||
>> -        (FoldedElementSize && Op1Pow == FoldedElementSize))
>> +          (FoldedElementSize && Op1Pow == FoldedElementSize))
>>        // ElementSize << log2(ArraySize)
>>        return Op0;
>>    }
>>
>>
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>

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