[Bug tree-optimization/108392] New: Unexpected optimization in presence of '__attribute__((noipa))'

[tschwinge at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108392

            Bug ID: 108392
           Summary: Unexpected optimization in presence of
                    '__attribute__((noipa))'
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tschwinge at gcc dot gnu.org
  Target Milestone: ---

Consider:

    __attribute__((noipa))
    int f(int n)
    {
      if (n < 0)
        n = f(-n);
      return n;
    }

For x86_64-pc-linux-gnu at recent commit
de99049f6fe5341024d4d939ac50d063280f90db, for '-O2' I see:

    --- 1.c.044t.phiopt1   2023-01-13 12:26:20.196625109 +0100
    +++ 1.c.045t.tailr1    2023-01-13 12:26:20.196625109 +0100
    [...]
     __attribute__((noipa, noinline, noclone, no_icf))
     int f (int n)
     {
       int _1;

       <bb 2> :
    -  gimple_cond <lt_expr, n_4(D), 0, NULL, NULL>
    +  # gimple_phi <n_4, n_8(D)(0), _1(3)>
    +  gimple_cond <lt_expr, n_4, 0, NULL, NULL>
         goto <bb 3>; [INV]
       else
         goto <bb 4>; [INV]

       <bb 3> :
    -  gimple_assign <negate_expr, _1, n_4(D), NULL, NULL>
    -  gimple_call <f, n_7, _1>
    +  gimple_assign <negate_expr, _1, n_4, NULL, NULL>
    +  goto <bb 2>; [INV]

       <bb 4> :
    -  # gimple_phi <n_2, n_4(D)(2), n_7(3)>
    +  # gimple_phi <n_2, n_4(2)>
       gimple_return <n_2>

     }

I was assuming that '__attribute__((noipa))' would inhibit optimizations such
as replacing a 'gimple_call' by knowledge of the body of the callee?

(This caused confusion in a different test case, where I didn't expect the
recursive function call to disappear.)