[LLVMdev] Partial loop unrolling

[Krzysztof Parzyszek]

On 7/15/2014 6:34 AM, Mahesha S wrote:
>
> As far as partial loop unrolling is concerned, I could see following
> three different possibilities. Assume that unroll factor is 3.
>
> Original loop:
>        for (i = 0; i < 10; i++)
>        {
>             do_foo(i);
>        }
>
> 1. First possibility
>        i = 0;
>        do_foo(i++);
>        do_foo(i++);
>        do_foo(i++);
>        for (; i < 10; i++)
>        {
>             do_foo(i);
>        }

This is really peeling, not unrolling.


> 2. Second possibility
>        for (i = 0; i < 7; i++)
>        {
>             do_foo(i);
>        }
>        do_foo(i++);
>        do_foo(i++);
>        do_foo(i++);

Same as above.


> 3. Third possibility
>        for (i = 0; i < 10;)
>        {
>             do_foo(i++);
>             do_foo(i++);
>             do_foo(i++);
>        }

This one is unrolled, but incorrectly.


-Krzysztof


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