[llvm-dev] generate vectorized code

[Mehdi Amini via llvm-dev]

> On Mar 18, 2016, at 1:47 PM, Rail Shafigulin <rail at esenciatech.com> wrote:
> 
> Yes this IR does not build or shuffle any vector. Try to write a function that takes 8 ints and a pointer to a <4xi32>, builds two vectors with the 8 ints,
> 
> This might sound like a dumb question, but how does one build a vector of ints out of regular ints in IR? 

See: http://llvm.org/docs/LangRef.html#vector-operations

In short, the IR has "insertelement", which maps to "INSERT_VECTOR_ELT" in SDAG and "extractelement", which maps to "EXTRACT_VECTOR_ELT" in SDAG.

I usually find good example by grepping in the lit tests. Another way is to write the function in clang, and run it with -O3 -emit-llvm -S to get a good starting point.

-- 
Mehdi



>  
> sum them, and store the result to the pointer.
> 
> 
>> 
>> In other words I left the code as is. 
>> 
>> However if I use a .c code and run it through clang, I don't see any vector instructions. I'm puzzled. What am I doing wrong? There seems to be a step missing, the one that will generate vectorized IR, but I can't seem to find how to do it.
> 
> Try: clang -O3 -emit-llvm -S test.c
> 
> -- 
> Mehdi
> 
> 
>> 
>> Any help on this is really appreciated.
>> 
>> -- 
>> Rail Shafigulin
>> Software Engineer 
>> Esencia Technologies
> 
> 
> 
> 
> -- 
> Rail Shafigulin
> Software Engineer 
> Esencia Technologies

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