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

[Mikhail Goncharov via Phabricator via llvm-commits]

goncharov reopened this revision.
goncharov added a comment.
This revision is now accepted and ready to land.

Hi @ABataev ,

I have found another regression on the latest version of this change:

  > cat repro.cc
  #include <cstdio>
  struct a {
    int b;
    int c;
    int o;
    int d;
  };
  class e {
  public:
    e(int);
    void f(a *);
    int g;
    int h;
    int i;
  };
  void e::f(a *p) {
    fprintf(stderr, "MiscompiledFunction\n");
    fprintf(stderr, "%d, %d, %d, %d, %d, %d\n", p->b, p->c, p->o, p->d, h, g);
    int j = (p->b + p->c) / 2, k = (p->o + p->d) / 2, l, m;
    switch (i) {
    case 0:
    case 2:
      l = h - 1 - j;
      m = g - 1 - k;
    }
    p->b = l + p->b - j;
    p->c = l + p->c - j;
    p->o = m + p->o - k;
    p->d = m + p->d - k;
  }
  int n = 0;
  e::e(int q) : g(0), h(0), i(q) {}
  int main() {
    a *bb = new a{0, 9, 4, 0}, *p = bb;
    e r(n);
    r.f(p);
    printf("%d %d %d %d\n", bb->b, bb->c, bb->o, bb->d);
  }
  > # at 5661317f864abf750cf893c6a4cc7a977be0995a
  > clang -Wall -Werror -Wextra -O3 -fno-exceptions -stdlib=libc++ -lc++ -std=gnu++17 repro.cc && ./a.out
  -9 0 -1 -5
  > # at bc69dd62c04a70d29943c1c06c7effed150b70e1
  > clang -Wall -Werror -Wextra -O3 -fno-exceptions -stdlib=libc++ -lc++ -std=gnu++17 repro.cc && ./a.out
  -7 2 -3 -7

It's quite fragile as e.g. removing `fprintf(stderr, "MiscompiledFunction\n");` or running with -fsanitize=null "fixes" the output.


Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D105020