[Bug ipa/81877] [7/8 Regression] Incorrect results with lto and -fipa-cp and -fipa-cp-clone

amonakov at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Thu Aug 17 16:51:00 GMT 2017


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81877

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |amonakov at gcc dot gnu.org

--- Comment #7 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Small C testcase demonstrating the issue with -O2 -fno-tree-sra:

void g(int *out)
{
  struct s {int x;} s;
#pragma GCC ivdep
  for (int i = 0; i < 100; i++)
    {
      int *x = &s.x;
      asm("" : "+r"(x));
      *x = 42;
      out[i] = s.x;
    }
}

I think the main question is how safelen introduced via pragma-ivdep or
do-concurrent is supposed to interact with addressable vars written in the loop
body? It doesn't seem well-defined?..


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