[PATCH] D105020: [SLP]Improve graph reordering.

[Mikhail Goncharov via Phabricator via llvm-commits]

goncharov added a comment.

Here is a repro I found

  $ cat ./repro.cc
  #include <iostream>
  namespace a {
  __attribute__((noinline)) void b(uint8_t *c, float *d, uint16_t e, uint16_t f) {
    uint16_t g = f;
    uint16_t h = c[0] << 2 | c[4] & 3;
    uint16_t l = c[1] << 2 | c[4] >> 2 & 3;
    uint16_t v = c[2] << 2 | 3;
    uint16_t j = c[3] << 2 | c[4] >> 6;
    *(d - 1) = float(l - e) / g;
    *(d - 2) = float(h - e) / g;
    *(d - 3) = float(j - e) / g;
    *(d - 4) = float(v - e) / g;
  }
  void bar(uint8_t *buffer, size_t k, size_t height, size_t, uint16_t e,
           uint16_t f, float *m) {
    int n = 24, g = f;
    float *t = &m[(24 - 2) * 4];
    size_t u = 2 * k;
    for (int o; o < height; o++) {
      uint8_t *p = buffer;
      uint8_t *q = p;
      float *r = &t[u];
      for (int a = 0; a < u; a += 4) {
        b(q, r, e, g);
        r -= 4;
      }
      t -= n;
    }
  }
  }  // namespace a
  int main() {
    uint8_t s[]{255, 0, 255, 0, 51};
    float m[4 * 24]{};
    a::bar(s, 4, 4, 0, 0, 1023, m);
    int *out = reinterpret_cast<int *>(m);
    int64_t sum;
    for (int i = 0; i < sizeof(m) / sizeof(int); i++) sum += out[i];
    std::cout << sum;
  }
  $ clang-before -O2 -std=gnu++17 repro.cc
  $ ./a.out
  17045651456
  $ clang-after -O2 -std=gnu++17 repro.cc
  $ ./a.out
  16609148640


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D105020/new/

https://reviews.llvm.org/D105020