[Bug middle-end/32521] New: [4.2] vrp_evaluate_conditional_warnv (tree-vrp.c:4186) at -O3 -ffast-math -ftree-vectorize -march=native

["jv244 at cam dot ac dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

as discussed in PR 29975 CP2K gets miscompiled by gfortran 4.2.0 (see comments
119 to 125). 

sources (src/all.f90) can be obtained from:

http://www.pci.unizh.ch/vandevondele/tmp/CP2K_gcc_2007_06.tgz

and are miscompiled with

-O3 -ffast-math -ftree-vectorize -march=native

the module that gets miscompiled is qs_neighbor_lists. 

under valgrind, compilation of that module shows:

valgrind --tool=memcheck
/data03/vondele/gcc_4_2_0/build/libexec/gcc/x86_64-unknown-linux-gnu/4.2.0/f951
qs_neighbor_lists.f90 -march=k8 -mtune=k8 -quiet -dumpbase
qs_neighbor_lists.f90 -auxbase qs_neighbor_lists -O3 -version -ffast-math
-ftree-vectorize -ftree-vectorizer-verbose=1 -I
/data03/vondele/gcc_4_2_0/build/lib/gcc/x86_64-unknown-linux-gnu/4.2.0/finclude
-o /tmp/ccoFFIrV.s


==30523== Conditional jump or move depends on uninitialised value(s)
==30523==    at 0x706E08: vrp_evaluate_conditional_warnv (tree-vrp.c:4186)
==30523==    by 0x706F9C: vrp_evaluate_conditional (tree-vrp.c:4318)
==30523==    by 0x4B6E9F: substitute_and_fold (tree-ssa-propagate.c:1053)
==30523==    by 0x700F04: execute_vrp (tree-vrp.c:5318)
==30523==    by 0x6F9F27: execute_one_pass (passes.c:881)
==30523==    by 0x6FA08B: execute_pass_list (passes.c:932)
==30523==    by 0x6FA09D: execute_pass_list (passes.c:933)
==30523==    by 0x48CCCD: tree_rest_of_compilation (tree-optimize.c:463)
==30523==    by 0x742363: cgraph_expand_function (cgraphunit.c:1244)
==30523==    by 0x742C8D: cgraph_optimize (cgraphunit.c:1309)
==30523==    by 0x4633DC: gfc_be_parse_file (f95-lang.c:307)
==30523==    by 0x6DBF92: toplev_main (toplev.c:1033)

as discussed in PR29975, the combination of options above is needed to trigger
the bug.


-- 
           Summary: [4.2] vrp_evaluate_conditional_warnv (tree-vrp.c:4186)
                    at -O3 -ffast-math -ftree-vectorize -march=native
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jv244 at cam dot ac dot uk


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32521