[PATCH] D12765: [LV] Allow vectorization of loops with induction post-inc expressions

[Jakub Kuderski via llvm-commits]

kuhar added a comment.

Hello Michael,

here is complete C code that is being vectorized now and wasn't previously. One could probably reduce it further, but this version preserves the main idea:

  #include <stdlib.h>
   
  #define BUFF_SIZE 4096
  
  void __attribute__((noinline))
      foo(int y, char *restrict src, char *restrict dest) {
    char *p = src;
    char *ptr = dest;
    int n = (y - 1) < (dest + BUFF_SIZE - ptr - 1)
                ? (y - 1)
                : (dest + BUFF_SIZE - ptr - 1);
    for (int vv = 0; vv < n; ++vv)
      *ptr++ = *p++;
  
    *ptr++ = *p++;
  
    printf("%d\n", ptr);
  }
  
  int main() {
    char S[] = "01234567890abcdefghij123456789abcdefghij0123456789XXX";
    char D[128] = { 0 };
    foo(33, S, D);
    printf("%s\n", D);
  }

I need this patch to perform some other optimizations (more advanced loop unrolling/vectorizing).

This patch triggers in real-life code. For example, it showed 24.54% improvement in `lnt.MultiSource/Benchmarks/MiBench/automotive-susan/automotive-susan` and 7.60% improvement in `lnt.SingleSource/Benchmarks/BenchmarkGame/recursive` on A57 in aarch64.


Repository:
  rL LLVM

http://reviews.llvm.org/D12765