------- Comment #8 from manu at gcc dot gnu dot org 2008-02-01 16:28 -------
(In reply to comment #6)
> Here is what happens (note that, differently from what was the case, now the
> warning is give three times in a row):
The "is used" warning is the same issue with virtual operands. The relevant
part is this:
# BLOCK 4, starting at line 3675
# PRED: 3 (true)
# LOADS: { zD.189596 }
[bug.cc : 3675] z.1883D.189607_8 = zD.189596;
[bug.cc : 3675] *toD.188165_6(D) ={v} z.1883D.189607_8;
[bug.cc : 3676] D.189608_9 = rD.189597_4;
[bug.cc : 3676] goto <bb 10>;
# SUCC: 10 (fallthru)
We see that zD.189596 has an empty definition, which is wrong since it has been
passed by reference in a previous BB. Again, it won't be fixed until we teach
Wuninitialized about VOPS.
The "may be used" warnings appear after applying inline, so we end up with
something like:
# BLOCK 25 freq:10000, starting at line 3670
# PRED: 3 [100.0%] (fallthru,exec) 6 [33.0%] (false,exec) 7 [100.0%]
(fallthru,exec) 8 [100.0%] (fallthru,exec) 12 [33.0%] (false,exec) 13
[100.0%] (fallthru,ex\
ec) 15 [69.0%] (false,exec) 16 [100.0%] (fallthru,exec) 19 [33.0%]
(false,exec) 20 [100.0%] (fallthru,exec) 22 [69.0%] (false,exec) 23 [100.0%]
(fallthru,exec) 24\
[100.0%] (fallthru,exec)
# zD.203060_41 = PHI <zD.203060_58(3), zD.203060_50(D)(6), zD.203060_51(7),
zD.203060_52(8), zD.203060_50(D)(12), zD.203060_53(13), zD.203060_50(D)(15),
zD.203060_54(\
16), zD.203060_50(D)(19), zD.203060_55(20), zD.203060_50(D)(22),
zD.203060_56(23), zD.203060_57(24)>
# D.222111_38 = PHI <4(3), 33(6), 2(7), 4(8), 33(12), 2(13), 18(15), 1(16),
33(19), 2(20), 18(22), 1(23), 4(24)>
D.222156_40 = D.222111_38;
[bug.cc : 3670] rD.203116_7 = D.222156_40;
[bug.cc : 3671] r.1882D.203125_9 = (intD.2) rD.203116_7;
[bug.cc : 3671] switch (r.1882D.203125_9)
Whether that is a correct PHI, I cannot tell because the testcase is too huge
for me to understand how that happened. Yet, we should not be warning for each
PHI operand, at a minimum.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33802
