[Bug middle-end/57287] [4.9 Regression] Bogous uninitialized warning with abnormal control flow

[xinliangli at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57287

--- Comment #16 from davidxl <xinliangli at gmail dot com> ---
(In reply to Richard Biener from comment #15)
> Confirmed.  David, can you have a look here?  I had a hard time following
> what
> exactly to do with the dataflow in the uninit pass for abnormal control flow
> (abnormal control flow should be considered receiving an initialized value).
> 
> Thanks.


I looked at it a little. The warning is not from the predicated uninit analysis
which checks uses of phi defs.  The warning is emitted from tree-ssa.c:1644 in
function warn_uninitialized_vars. It warns about the 'definitely' uninitialized
variable that may be executed. In this case it is use of 'buf_16(ab)' in BB3. 
Not sure where this statement comes from:

buf_24 = buf_16(ab);

The dot file is attached.

digraph "uninit.c.131t.uninit1" {
overlap=false;
subgraph "baz" {
    color="black";
    label="baz";
    fn_11_basic_block_0
[shape=Mdiamond,style=filled,fillcolor=white,label="ENTRY"];

    fn_11_basic_block_1
[shape=Mdiamond,style=filled,fillcolor=white,label="EXIT"];

    fn_11_basic_block_2 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:10000 |\<bb\ 2\>:\l\
|varseen_11(ab)\ =\ 0;\l\
|_14\ =\ head\ ();\l\
}"];

    fn_11_basic_block_3 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:7100 |\<bb\ 3\>:\l\
|list\ =\ _14;\l\
|buf_24\ =\ buf_16(ab);\l\
|if\ (_14\ !=\ 0B)\l\
\ \ goto\ \<bb\ 4\>;\l\
else\l\
\ \ goto\ \<bb\ 8\>;\l\
}"];

    fn_11_basic_block_4 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:8500 |\<bb\ 4\>:\l\
|#\ varseen_3(ab)\ =\ PHI\ \<1(3),\ 1(6)\>\l\
|#\ n_26(ab)\ =\ PHI\ \<_14(3),\ n_2(ab)(6)\>\l\
|#\ buf_27(ab)\ =\ PHI\ \<buf_24(3),\ buf_7(ab)(6)\>\l\
|buf_21\ =\ bar\ ();\l\
}"];

    fn_11_basic_block_5 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:4250 |\<bb\ 5\>:\l\
}"];

    fn_11_basic_block_6 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:2900 |\<bb\ 6\>:\l\
|#\ n_1(ab)\ =\ PHI\ \<n_15(ab)(2),\ n_26(ab)(4),\ n_26(ab)(5)\>\l\
|#\ varseen_4(ab)\ =\ PHI\ \<varseen_11(ab)(2),\ varseen_3(ab)(4),\
varseen_3(ab)(5)\>\l\
|#\ buf_6(ab)\ =\ PHI\ \<buf_16(ab)(2),\ buf_27(ab)(4),\ buf_21(5)\>\l\
|__sigsetjmp\ (buf_6(ab),\ 1);\l\
|n_19\ =\ n_1(ab)-\>next;\l\
|n_2(ab)\ =\ n_19;\l\
|varseen_5\ =\ varseen_4(ab);\l\
|buf_7(ab)\ =\ buf_6(ab);\l\
|if\ (n_2(ab)\ !=\ 0B)\l\
\ \ goto\ \<bb\ 4\>;\l\
else\l\
\ \ goto\ \<bb\ 7\>;\l\
}"];

    fn_11_basic_block_7 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:1500 |\<bb\ 7\>:\l\
|_25\ =\ varseen_5;\l\
}"];

    fn_11_basic_block_8 [shape=record,style=filled,fillcolor=lightgrey,label="{
FREQ:1500 |\<bb\ 8\>:\l\
|#\ _8\ =\ PHI\ \<_25(7),\ 0(3)\>\l\
|return\ _8;\l\
}"];

    fn_11_basic_block_0:s -> fn_11_basic_block_2:n
[style="solid,bold",color=blue,weight=100,constraint=true, label="[100%]"];
    fn_11_basic_block_2:s -> fn_11_basic_block_6:n
[style="solid,bold",color=red,weight=10,constraint=true, label="[29%]"];
    fn_11_basic_block_2:s -> fn_11_basic_block_3:n
[style="solid,bold",color=blue,weight=100,constraint=true, label="[71%]"];
    fn_11_basic_block_3:s -> fn_11_basic_block_4:n
[style="solid,bold",color=black,weight=10,constraint=true, label="[85%]"];
    fn_11_basic_block_3:s -> fn_11_basic_block_8:n
[style="solid,bold",color=black,weight=10,constraint=true, label="[15%]"];
    fn_11_basic_block_4:s -> fn_11_basic_block_6:n
[style="dotted,bold",color=red,weight=10,constraint=false, label="[50%]"];
    fn_11_basic_block_4:s -> fn_11_basic_block_5:n
[style="solid,bold",color=blue,weight=100,constraint=true, label="[50%]"];
    fn_11_basic_block_5:s -> fn_11_basic_block_6:n
[style="dotted,bold",color=blue,weight=10,constraint=false, label="[100%]"];
    fn_11_basic_block_6:s -> fn_11_basic_block_4:n
[style="solid,bold",color=black,weight=10,constraint=true, label="[85%]"];
    fn_11_basic_block_6:s -> fn_11_basic_block_7:n
[style="solid,bold",color=black,weight=10,constraint=true, label="[15%]"];
    fn_11_basic_block_7:s -> fn_11_basic_block_8:n
[style="solid,bold",color=blue,weight=100,constraint=true, label="[100%]"];
    fn_11_basic_block_8:s -> fn_11_basic_block_1:n
[style="solid,bold",color=black,weight=10,constraint=true, label="[100%]"];
    fn_11_basic_block_0:s -> fn_11_basic_block_1:n
[style="invis",constraint=true];
}
}