[LLVMdev] How doesn't llvm generate IR for logical negate operation

zhi chen
2015-04-11T00:29:54Z

Thanks, Bruce. So, what is the easiest way to check if there is any bit set
to 1 in a <N x i1> vector type? I used bitcast instruction to cast it into
"iN" first and them compare iN to 0. Do you have a better way to do
it?
Thanks again.

On Fri, Apr 10, 2015 at 5:22 PM, Bruce Hoult <bruce at hoult.org> wrote:

> LLVM doesn't have a "logical neg" (or "not")
operator. That's a C thing.
> Do a compare against 0 to create an i1 result, then zero extend the i1 to
> the size of integer result you want.
>
>
> On Sat, Apr 11, 2015 at 12:07 PM, zhi chen <zchenhn at gmail.com>
wrote:
>
>> How can I generate LLVM IR for both logical NEG (!)? For example, if I
>> have Int32Ty a,
>>
>> For the bitwise NEG(~):
>>
>> c = ~a ;
>>
>> I can use the following API from LLVM:
>>
>> BinaryOperator *neg = BinaryOperator::CreateNeg(nbits,
"bitwiseNEG", insertBefore);
>>
>> How, if I want to generate logical NEG:
>>
>> c = !a;
>>
>> what should I do for this?
>>
>> Thanks
>>
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>
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