https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87746
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ick. if-conversion leaves us with quite a mess:
<bb 3> [local count: 955630224]:
# i_20 = PHI <i_17(10), 0(21)>
_1 = replacements[i_20].subreg_loc;
_2 = (long int) y_13(D);
_3 = (struct rtx_def * *) _2;
_ifc__42 = replacements[i_20].subreg_loc;
_ifc__43 = _3;
_ifc__44 = _1 == x_12(D) ? _ifc__43 : _ifc__42;
replacements[i_20].subreg_loc = _ifc__44;
_4 = replacements[i_20].where;
_22 = _1 == x_12(D);
_9 = ~_22;
_18 = _4 == x_12(D);
_19 = _9 & _18;
_5 = (long int) y_13(D);
_6 = (struct rtx_def * *) _5;
_ifc__45 = replacements[i_20].where;
_ifc__46 = _6;
_ifc__47 = _19 ? _ifc__46 : _ifc__45;
replacements[i_20].where = _ifc__47;
_ifc__48 = replacements[i_20].subreg_loc;
_ifc__49 = 0B;
_ifc__50 = _19 ? _ifc__49 : _ifc__48;
replacements[i_20].subreg_loc = _ifc__50;
i_17 = i_20 + 1;
if (n_replacements_11(D) > i_17)
goto <bb 10>; [89.00%]
else
goto <bb 8>; [11.00%]
throwing VN on if-converted loops improves this to the following also avoiding
the ICE:
<bb 3> [local count: 955630224]:
# i_20 = PHI <i_17(10), 0(21)>
_1 = replacements[i_20].subreg_loc;
_2 = (long int) y_13(D);
_3 = (struct rtx_def * *) _2;
_ifc__44 = _1 != x_12(D) ? _1 : _3;
replacements[i_20].subreg_loc = _ifc__44;
_4 = replacements[i_20].where;
_22 = _1 == x_12(D);
_9 = ~_22;
_18 = _4 == x_12(D);
_19 = _9 & _18;
_ifc__47 = _19 ? _3 : _4;
replacements[i_20].where = _ifc__47;
_ifc__50 = _19 ? 0B : _ifc__44;
replacements[i_20].subreg_loc = _ifc__50;
i_17 = i_20 + 1;
if (n_replacements_11(D) > i_17)
goto <bb 10>; [89.00%]
else
goto <bb 8>; [11.00%]
The dead store is of course still confusing us. My old store-commoning
patch would maybe help here. Or a region-based DSE. Or somehow
integrating basic DSE with VN.
Anyhow the ICE is still odd.
