[Bug lto/82027] New: wrong code with -O3 -flto

["ssbssa at yahoo dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82027

            Bug ID: 82027
           Summary: wrong code with -O3 -flto
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ssbssa at yahoo dot de
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 42082
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42082&action=edit
test case

With the attached file I get a division by 0 when using "-O3 -flto", but not
with "-O2 -flto" or just "-O3".
Fails with 7.1.0 and 7.2.0, but not with 6.3.0.


$ g++ -O3 -flto -g -odiv0 div0.cpp

$ gdb -q div0
Reading symbols from div0...done.
(gdb) r
Starting program: C:\qiewer\div0.exe
[New Thread 1768.0x4e0]

Program received signal SIGFPE, Arithmetic exception.
0x000000000040f8f3 in calcPercent (name=0x411000 "", size=0, pos=4263936,
    this=0x3b1f60) at div0.cpp:49
49            int percent = 100*pos/size;
(gdb) bt
#0  0x000000000040f8f3 in calcPercent (name=0x411000 "", size=0, pos=4263936,
    this=0x3b1f60) at div0.cpp:49
#1  Looper::loop() () at div0.cpp:23
#2  main (argc=<optimized out>, argv=<optimized out>) at div0.cpp:64
(gdb) kill
Kill the program being debugged? (y or n) [answered Y; input not from terminal]
(gdb) quit