[llvm-commits] [llvm] r145249 - /llvm/trunk/include/llvm/ADT/APInt.h

[Benjamin Kramer]

On 28.11.2011, at 18:06, Eli Friedman wrote:

> On Mon, Nov 28, 2011 at 8:56 AM, Benjamin Kramer
> <benny.kra at googlemail.com> wrote:
>> Author: d0k
>> Date: Mon Nov 28 10:56:38 2011
>> New Revision: 145249
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=145249&view=rev
>> Log:
>> Handle more cases in APInt::getLowBitsSet's fast path.
>> 
>> Modified:
>>    llvm/trunk/include/llvm/ADT/APInt.h
>> 
>> Modified: llvm/trunk/include/llvm/ADT/APInt.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=145249&r1=145248&r2=145249&view=diff
>> ==============================================================================
>> --- llvm/trunk/include/llvm/ADT/APInt.h (original)
>> +++ llvm/trunk/include/llvm/ADT/APInt.h Mon Nov 28 10:56:38 2011
>> @@ -497,8 +497,8 @@
>>     if (loBitsSet == APINT_BITS_PER_WORD)
>>       return APInt(numBits, -1ULL);
> 
> Did you mean to delete these two lines?

Yes, I should've made clear that this change supersedes the old path, loBitsSet is always less or equal numBits.

-Ben

> 
> -Eli
> 
>>     // For small values, return quickly.
>> -    if (numBits < APINT_BITS_PER_WORD)
>> -      return APInt(numBits, (1ULL << loBitsSet) - 1);
>> +    if (loBitsSet <= APINT_BITS_PER_WORD)
>> +      return APInt(numBits, -1ULL >> (APINT_BITS_PER_WORD - loBitsSet));
>>     return getAllOnesValue(numBits).lshr(numBits - loBitsSet);
>>   }