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    • Nadav Rotem's avatar
      Add support for bottom-up SLP vectorization infrastructure. · 2d9dec32
      Nadav Rotem authored
      This commit adds the infrastructure for performing bottom-up SLP vectorization (and other optimizations) on parallel computations.
      The infrastructure has three potential users:
      
        1. The loop vectorizer needs to be able to vectorize AOS data structures such as (sum += A[i] + A[i+1]).
      
        2. The BB-vectorizer needs this infrastructure for bottom-up SLP vectorization, because bottom-up vectorization is faster to compute.
      
        3. A loop-roller needs to be able to analyze consecutive chains and roll them into a loop, in order to reduce code size. A loop roller does not need to create vector instructions, and this infrastructure separates the chain analysis from the vectorization.
      
      This patch also includes a simple (100 LOC) bottom up SLP vectorizer that uses the infrastructure, and can vectorize this code:
      
      void SAXPY(int *x, int *y, int a, int i) {
        x[i]   = a * x[i]   + y[i];
        x[i+1] = a * x[i+1] + y[i+1];
        x[i+2] = a * x[i+2] + y[i+2];
        x[i+3] = a * x[i+3] + y[i+3];
      }
      
      llvm-svn: 179117
      2d9dec32
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