[Bug regression/42282] New: regression: ICE when bootstrapping trunk with -O2 -funswitch-loops

["matt at use dot net" <gcc-bugzilla at gcc dot gnu dot org>]

With 20091201 trunk on Linux/amd64 ICE does not happen with GCC 4.4.1-ubuntu8.
Appears to be bad interaction 
between -O2 and -funswitch-loops. Either alone is fine, but together the crash
occurs. The commandline below reproduces the issue, but removing all but -O2
and -funswitch-loops will also reproduce.

gcc -c  -g -fkeep-inline-functions -DIN_GCC   -W -Wall -Wwrite-strings
-Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wmissing-format-attribute
-pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings
-Wold-style-definition -Wc++-compat -fno-common  -DHAVE_CONFIG_H -I. -I.
-I../../gcc-trunk/gcc -I../../gcc-trunk/gcc/. -I../../gcc-trunk/gcc/../include
-I../../gcc-trunk/gcc/../libcpp/include  -I../../gcc-trunk/gcc/../libdecnumber
-I../../gcc-trunk/gcc/../libdecnumber/bid -I../libdecnumber 
-DCLOOG_PPL_BACKEND  -I/usr/include/libelf -O2 -floop-interchange
-floop-strip-mine -floop-block -findirect-inlining -ftree-switch-conversion
-fvect-cost-model -fgcse-sm -fgcse-las -fgcse-after-reload -fsee
-ftree-loop-linear -ftree-loop-distribution -ftree-loop-im -ftree-loop-ivcanon
-fivopts -fvpt -funroll-loops -funswitch-loops
../../gcc-trunk/gcc/simplify-rtx.c -o simplify-rtx.o
../../gcc-trunk/gcc/simplify-rtx.c: In function
‘simplify_immed_subreg’:
../../gcc-trunk/gcc/simplify-rtx.c:4829:1: error: definition in block 35 does
not dominate use in block 131
for SSA_NAME: vp_549 in statement:
# DEBUG vp => vp_549 + 1
../../gcc-trunk/gcc/simplify-rtx.c:4829:1: internal compiler error: verify_ssa
failed


-- 
           Summary: regression: ICE when bootstrapping trunk with -O2 -
                    funswitch-loops
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: regression
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: matt at use dot net
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42282