[LLVMdev] vector compare

[Claudio Basile]

On Dec 25, 2008, at 11:02 AM, Eli Friedman wrote:

> On Thu, Dec 25, 2008 at 1:54 AM, Eli Friedman  
> <eli.friedman at gmail.com> wrote:
>> On Thu, Dec 25, 2008 at 1:28 AM, Claudio Basile <cbasile at tempo- 
>> da.com> wrote:
>>> Hi all,
>>>
>>> is there any way to compare two 128bit values?
>>> I have tried 3 different approaches and they all fail with an  
>>> internal
>>> assertion.
>>> I'm running llvm 2.4 on x86 with the following command line:
>>>
>>>> llvm-as test.ll -o test.bc
>>>> llc test.bc -filetype=asm
>>>
>>> I would expect the code generator to emit a sequence of SSE
>>> instructions.
>>
>> Approaches 1 and 2 depend on some stuff that hasn't really stabilized
>> yet... you should get much better results with vicmp.
>
> Oh wait, I just realized vicmp is a post-2.4 thing... if you really
> want to generate an SSE comparison using LLVM 2.4, you can use the x86
> intrinsics, like @llvm.x86.sse2.pcmpeq.b.

Thanks for your answer.
It looks like vicmp is part of LLVM 2.4. It is documented there, at  
least.
How do you suggest I use it to compare two vector operands?
I'd guess I could generate a mask by extracting the most significant  
bits in each words, but that approach doesn't work per my initial  
posting.

Claudio