This testcase fails for:

gcc -O2 -msse2 -mtune=k8 sse2-vec-6.c

Analyzing compilation unit
Performing interprocedural optimizations
 <visibility> <early_local_cleanups> <inline> <static-var> <pure-const> <type-escape-var>Assembling functions:
 i386_cpuid_ecx i386_cpuid_edx i386_extended_cpuid_ecx i386_extended_cpuid_edx sse2_test
sse2-vec-6.c: In function âsse2_testâ:
sse2-vec-6.c:69: internal compiler error: in expand_simple_binop, at optabs.c:1214
Please submit a full bug report,

Backtrace:

#0  fancy_abort (file=0x8701de4 "../../gcc-svn/trunk/gcc/optabs.c", line=1214, function=0x87022f2 "expand_simple_binop") at ../../gcc-svn/trunk/gcc/diagnostic.c:656
#1  0x082706e7 in expand_simple_binop (mode=V2SFmode, code=VEC_SELECT, op0=0xb795a57c, op1=0xb792c938, target=0xb795c350, unsignedp=1, methods=OPTAB_LIB_WIDEN) at ../../gcc-svn/trunk/gcc/optabs.c:1214
#2  0x081a5edb in force_operand (value=0xb795a5ac, target=0xb795c350) at ../../gcc-svn/trunk/gcc/expr.c:6084
#3  0x086144ab in move_invariant_reg (loop=0xb794ef74, invno=0) at ../../gcc-svn/trunk/gcc/loop-invariant.c:1178
#4  0x0861580d in move_loop_invariants () at ../../gcc-svn/trunk/gcc/loop-invariant.c:1240
#5  0x086137d5 in rtl_move_loop_invariants () at ../../gcc-svn/trunk/gcc/loop-init.c:239
#6  0x08276976 in execute_one_pass (pass=0x87c7280) at ../../gcc-svn/trunk/gcc/passes.c:1067

The problem is that we enter force_operand() with:

(gdb) p debug_rtx (value)
(vec_select:V2SF (subreg:V4SF (reg:V2DI 91 [ pretmp.201 ]) 0)
    (parallel [
            (const_int 0 [0x0])
            (const_int 1 [0x1])
        ]))

There is no optab for vec_select, and we crash later in assert in expand_simple_optab() on uninitialized optab.

The failure is actually the same as in PR26449, however the solution [1] looks rather suspicious to me, as force_operand() won't return NULL, but would crash via expand_simple_optab() for RTXs without optab.

[1] http://gcc.gnu.org/ml/gcc-patches/2006-06/msg00313.html