[LLVMdev] Decouple LoopVectorizer from O3

[Anadi Mishra]

Hi Nadav,

I tried your suggestion by changing the condition to :

189   if (LoopVectorize && OptLevel >= 0)
190     MPM.add(createLoopVectorizePass());

and compiled. Then I used the following command:

opt -mtriple=x86_64-linux-gnu -vectorize-loops
-vectorizer-min-trip-count=6 -debug-only=loop-vectorize -O1-S -o
example1_vect.s example1.s

where example1.s is IR generated by

clang -S -emit-llvm example1.c

example1.c contains the following loop:

for(int i=0;i<SIZE;i++)
        {
                aa[i] = bb[i] + count;
                count++;
                printf("a[%d] is %d", i,aa[i]);
        }

LV runs and says "LV: Found too many inductions".

I am guessing that this because some of the loop passes are missing.
Could you please shed some light on what passes should be used to
prepare the IR for LV?


Best,
Anadi


On Thu, Apr 11, 2013 at 2:48 AM, Nadav Rotem <nrotem at apple.com> wrote:
>
> Hi Anadi,
>
> In the file PassManagerBuilder.cpp you can change the lines below to get rid of the O3 restriction.
>
> 189   if (LoopVectorize && OptLevel > 2)
> 190     MPM.add(createLoopVectorizePass());
>
> Nadav
>
>
>
>
> On Apr 10, 2013, at 5:39 PM, Anadi Mishra <reachanadi at gmail.com> wrote:
>
> Hello,
>
> I am trying out the LoopVectorizer(LV) pass and would like to decouple it from O3 which is currently required to run LV. I want to do this because I want to understand the behaviour of LV by trying simple loops but the O3 mostly optimises away the loop body.
>
> Any ideas would be appreciated.
>
> Best,
> Anadi.
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