[Bug middle-end/55481] [4.8 regression] -O2 generates a wrong-code infinite loop in C++Benchmark's simple_types_constant_folding int8 xor test

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55481



Richard Biener <rguenth at gcc dot gnu.org> changed:



           What    |Removed                     |Added

----------------------------------------------------------------------------

             Status|UNCONFIRMED                 |NEW

   Last reconfirmed|                            |2012-11-27

   Target Milestone|---                         |4.8.0

     Ever Confirmed|0                           |1



--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2012-11-27 
10:40:45 UTC ---

Infinite loops are a sign for out-of-bound array accesses, 4.8 now very

aggressively exploits undefined behavior that this triggers.



Btw, it also happens when I declare data8 as



int8_t data8[SIZE*2 ];



so it does look like genuine bug in GCC.  It loops in



#0  0x00000000004009cc in test_constant<signed char, custom_or_constants<signed

char> > (count=13, label=0x4012da "int8_t or constants", 

    first=0x6020d0 <data8> '\001' <repeats 13 times>)

    at benchmark_shared_tests.h:661



btw.