[Bug tree-optimization/109154] [13 regression] jump threading de-optimizes nested floating point comparisons

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109154

--- Comment #26 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The above slightly simplified (dead var removal, preprocessing etc.):
typedef struct __attribute__((__packed__)) _Atom { float x, y, z; int type; }
Atom;
typedef struct __attribute__((__packed__)) _FFParams { int hbtype; float
radius; float hphb; float elsc; } FFParams;

void
fasten_main (unsigned long group, unsigned long natlig, unsigned long natpro,
const Atom *protein, const Atom *ligand,
             const FFParams *forcefield, float *energies)
{
  float etot[64];
  float lpos_x[64];
  for (int l = 0; l < 64; l++) {
    etot[l] = 0.f;
    lpos_x[l] = 0.f;
  }
  for (int il = 0; il < natlig; il++) {
    const Atom l_atom = ligand[il];
    const FFParams l_params = forcefield[l_atom.type];
    for (int ip = 0; ip < natpro; ip++) {
      const Atom p_atom = protein[ip];
      const FFParams p_params = forcefield[p_atom.type];
      const float radij = p_params.radius + l_params.radius;
      const float elcdst = (p_params.hbtype == 70 && l_params.hbtype == 70) ?
4.0f : 2.0f;
      const float elcdst1 = (p_params.hbtype == 70 && l_params.hbtype == 70) ?
0.25f : 0.5f;
      const int type_E = ((p_params.hbtype == 69 || l_params.hbtype == 69));
      const float chrg_init = l_params.elsc * p_params.elsc;
      for (int l = 0; l < 64; l++) {
        const float x = lpos_x[l] - p_atom.x;
        const float distij = (x * x);
        const float distbb = distij - radij;
        const int zone1 = (distbb < 0.0f);
        float chrg_e = chrg_init * ((zone1 ? 1.0f : (1.0f - distbb * elcdst1))
* (distbb < elcdst ? 1.0f : 0.0f));
        float neg_chrg_e = -__builtin_fabsf(chrg_e);
        chrg_e = type_E ? neg_chrg_e : chrg_e;
        etot[l] += chrg_e * 45.0f;
      }
    }
  }
  for (int l = 0; l < 64; l++)
    energies[group * 64 + l] = etot[l] * 0.5f;
}

The r13-2266 to r13-2267 diff indeed starts during threadfull1, the dump says:
...
  Registering killing_def (path_oracle) distbb_75
- Registering value_relation (path_oracle) (iftmp.0_32 <= distbb_75) (root:
bb16)
-path: 16->18->xx REJECTED
-Checking profitability of path (backwards):  bb:18 (3 insns) bb:16 (6 insns)
bb:23
-  Control statement insns: 2
-  Overall: 7 insns
-
- Registering killing_def (path_oracle) distbb_75
- Registering value_relation (path_oracle) (iftmp.0_32 <= distbb_75) (root:
bb23)
-path: 23->16->18->xx REJECTED
-Checking profitability of path (backwards):  bb:18 (3 insns) bb:16 (6 insns)
bb:23 (3 insns) bb:15
-  Control statement insns: 2
-  Overall: 10 insns
-  FAIL: Did not thread around loop and would copy too many statements.
-Checking profitability of path (backwards):  bb:18 (3 insns) bb:16 (6 insns)
bb:23 (3 insns) bb:22 (latch)
-  Control statement insns: 2
-  Overall: 10 insns
-  FAIL: Did not thread around loop and would copy too many statements.
+Checking profitability of path (backwards): 
+  [10] Registering jump thread: (16, 18) incoming edge;  (18, 20) nocopy; 
+path: 16->18->20 SUCCESS
 Checking profitability of path (backwards):  bb:20 (7 insns) bb:18
   Control statement insns: 2
   Overall: 5 insns
...
etc.  Though, I know nothing about the threader and don't see suspect ranges in
the decisions there.