[llvm-dev] Query on unswitching + vectorization

[Gopalasubramanian, Ganesh via llvm-dev]

Hi,

I am going through analysis on unswitching + vectorization.
For the below test, llvm unswitches successfully but fails to vectorize the loop after unswitching.
Llvm bails out saying "Found an outside user" apparently which is the value of 'tmp'.

int i, w, x[1000], y[1000],tmp;
void fn()
{
  for (i = 0; i < 1000; i++) {
    if (w==1) {
        y[i] = 1; tmp = i*2;
    }
    else if (w==2) {
        y[i] = 2; tmp = i*4;
    }
    x[i] += y[i] + tmp;
  }
}

GCC vectorizes the loop after unswitching/if conversion. Request your help in vectorizing this loop.

Regards
Ganesh

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