[llvm-dev] clang/llc is just hanging during instruction selection

[Rail Shafigulin via llvm-dev]

I've been told that clang/llc is handing because I'm creating a cycle in my
instruction selection. I'm trying to figure out where exactly but
unfortunately my knowledge is quite limited. I'd appreciate if someone
could point me in the right direction.

Here is the test file I'm using:
#define N 32

int foo () {

  int a[N], b[N], c[N];

  for (int i = 0; i < N; ++i)
       c[i] = a[i] + b[i];

  int sum = 0;
  for (int i =0; i < N; i++)
    sum += c[i];

  return sum;

}

I generate a .ll file using
clang --target=esencia z.c -S -emit-llvm -o z.esencia.ll -O3

And then I run llc using
llc -mcpu=esencia -march=esencia z.esencia.ll -o z.esencia.s -O3
-debug-only=isel


setOperationAction(ISD::BUILD_VECTOR,      MVT::v4i32, Expand);
setOperationAction(ISD::EXTRACT_VECTOR_ELT,      MVT::v4i32, Expand);
setOperationAction(ISD::VECTOR_SHUFFLE,      MVT::v4i32, Expand);

At this point llc just hangs. I was explained that I create a cycle

I know that these three lines cause a problem (since none existed before I
added them), but unfortunately my knowledge is limited and I have hard time
understanding how I created it. Would someone be able to help me out?

The contents of the .ll file is located here: http://pastebin.com/daHnJWwB

The output of the

llc -mcpu=esencia -march=esencia z.esencia.ll -o z.esencia.s -O3
-debug-only=isel

command is provided here: http://pastebin.com/ErDaxJ4J

I realize that the output is quite big and would love find a way to reduce,
but quite frankly I'm not sure how to do it. I tried using bugpoint but it
hung as well.

I would really appreciate any help on this, i.e. how am i creating cycles
and how to eliminate them?





-- 
Rail Shafigulin
Software Engineer
Esencia Technologies
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