https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70103
Bug ID: 70103
Summary: gcc reports bad dependence and bails out of
vectorization for one of the bwaves loops.
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vekumar at gcc dot gnu.org
Target Milestone: ---
flux_lam.f:68:0: note: dependence distance = 0.
flux_lam.f:68:0: note: dependence distance == 0 between
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244] and
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244]
flux_lam.f:68:0: note: READ_WRITE dependence in interleaving.
flux_lam.f:68:0: note: bad data dependence.
Looking at vector dumps, if we have CSEd the load, then there is no dependency
issue here.
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244] = _272
_323 = MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244];
---snip---
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244] = _272;
# VUSE <.MEM_273>
_274 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_219];
# VUSE <.MEM_273>
_275 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_224];
_276 = _274 - _275;
_277 = ((_276));
t1_278 = _277 / dy2_68;
_279 = _195 + 3;
# VUSE <.MEM_273>
_280 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_252];
# VUSE <.MEM_273>
_281 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_254];
_282 = _280 - _281;
_283 = ((_282));
_284 = _283 / dy2_68;
_285 = t1_278 + _284;
_286 = ((_285));
_287 = _286 * 5.0e-1;
# VUSE <.MEM_273>
_288 = MEM[(real(kind=8)D.18[0:D.3601] *)v.107_60][_206];
# VUSE <.MEM_273>
_289 = MEM[(real(kind=8)D.18[0:D.3601] *)v.107_60][_203];
_290 = _288 - _289;
_291 = ((_290));
_292 = _291 / _64;
_293 = _287 + _292;
_294 = ((_293));
_295 = t0_210 * _294;
# .MEM_296 = VDEF <.MEM_273>
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_279] = _295;
# VUSE <.MEM_296>
_297 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_233];
# VUSE <.MEM_296>
_298 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_239];
_299 = _297 - _298;
_300 = ((_299));
t2_301 = _300 / dz2_71;
_302 = _195 + 4;
# VUSE <.MEM_296>
_303 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_261];
# VUSE <.MEM_296>
_304 = MEM[(real(kind=8)D.18[0:D.3605] *)u.105_58][_263];
_305 = _303 - _304;
_306 = ((_305));
_307 = _306 / dz2_71;
_308 = t2_301 + _307;
_309 = ((_308));
_310 = _309 * 5.0e-1;
# VUSE <.MEM_296>
_311 = MEM[(real(kind=8)D.18[0:D.3597] *)w.109_62][_206];
# VUSE <.MEM_296>
_312 = MEM[(real(kind=8)D.18[0:D.3597] *)w.109_62][_203];
_313 = _311 - _312;
_314 = ((_313));
_315 = _314 / _64;
_316 = _310 + _315;
_317 = ((_316));
_318 = t0_210 * _317;
# .MEM_319 = VDEF <.MEM_296>
MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_302] = _318;
_320 = _195 + 5;
_321 = _246 + _247;
_322 = ((_321));
# VUSE <.MEM_319>
_323 = MEM[(real(kind=8)D.18[0:D.3627] *)ev_197(D) clique 1 base 12][_244];
---snip---
