Crashes in world built w/ clang: FP registers?

Hi everyone,

Using clang as the default compiler, the kernel and drivers will work
fine, but a lot of programs in the base system and ports will crash w/
SIGBUS.  In fact, so much of the stuff in the chroot'ed world will
crash (everything from csh to gcc) that it's basically unusable.  I
finally got around to building w/ debug symbols, and ran gdb on a
coredump generated while I was trying to use tab completion in csh:

(gdb) bt
#0  tw_collect (command=dwarf2_read_address: Corrupted DWARF expression.)
    at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:1308
#1  0x000000000042777b in t_search (word=Unhandled dwarf expression opcode 0x0)
    at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:1725
#2  0x0000000000426829 in tenematch (inputline=Variable "inputline" is
not avail               able.)
    at /usr/src/bin/csh/../../contrib/tcsh/tw.parse.c:301
#3  0x000000000043545d in Inputl ()
    at /usr/src/bin/csh/../../contrib/tcsh/ed.inputl.c:415
#4  0x0000000000417a90 in readc (wanteof=Variable "wanteof" is not available.)
    at /usr/src/bin/csh/../../contrib/tcsh/sh.lex.c:1653
#5  0x0000000000416f37 in lex (hp=Variable "hp" is not available.)
    at /usr/src/bin/csh/../../contrib/tcsh/sh.lex.c:162
#6  0x0000000000405afb in process (catch=Unhandled dwarf expression opcode 0x0)
    at /usr/src/bin/csh/../../contrib/tcsh/sh.c:1922
#7  0x0000000000404b51 in main (argc=Variable "argc" is not available.)
    at /usr/src/bin/csh/../../contrib/tcsh/sh.c:1289

gdb) disas
Dump of assembler code for function tw_collect:
0x00000000004288b0 <tw_collect+0>:      push   %rbp
0x00000000004288b1 <tw_collect+1>:      mov    %rsp,%rbp
0x00000000004288b4 <tw_collect+4>:      push   %r15
0x00000000004288b6 <tw_collect+6>:      push   %r14
0x00000000004288b8 <tw_collect+8>:      push   %r13
0x00000000004288ba <tw_collect+10>:     push   %r12
0x00000000004288bc <tw_collect+12>:     push   %rbx
0x00000000004288bd <tw_collect+13>:     sub    $0x2e8,%rsp
0x00000000004288c4 <tw_collect+20>:     mov    %r9,-0x308(%rbp)
0x00000000004288cb <tw_collect+27>:     mov    %r8,-0x300(%rbp)
0x00000000004288d2 <tw_collect+34>:     mov    %rcx,-0x2f8(%rbp)
0x00000000004288d9 <tw_collect+41>:     mov    %rdx,-0x2f0(%rbp)
0x00000000004288e0 <tw_collect+48>:     mov    %esi,-0x2e8(%rbp)
0x00000000004288e6 <tw_collect+54>:     mov    %edi,-0x2e4(%rbp)
0x00000000004288ec <tw_collect+60>:     movl   $0x0,-0x1d4(%rbp)
0x00000000004288f6 <tw_collect+70>:     movaps 0x23115b(%rip),%xmm0
    # 0x6                                                   59a58
<reslab+48>
0x00000000004288fd <tw_collect+77>:     lea    -0x2(%rdi),%eax
0x0000000000428900 <tw_collect+80>:     mov    %eax,-0x2e0(%rbp)
0x0000000000428906 <tw_collect+86>:     test   %edi,%edi
0x0000000000428908 <tw_collect+88>:     movaps %xmm0,-0x210(%rbp)
0x000000000042890f <tw_collect+95>:     sete   %al
---Type <return> to continue, or q <return> to quit---q
Quit
(gdb) info line tw.parse.c:1308
Line 1308 of "/usr/src/bin/csh/../../contrib/tcsh/tw.parse.c"
   starts at address 0x4288f6 <tw_collect+70>
   and ends at 0x4288fd <tw_collect+77>.


Looks like it's crashing as soon as it tries to use the XMM registers.
 I'm not sure if all of the crashes I'm getting are like this one, but
I was surprised to see FP registers in code like this.

I'm using march=corei7 and -O2 for both world and kernel, but using
march=nocona or just leaving out CPUTYPE has no effect (actual CPU is
Nehalem Xeon 5520)
Here's the relevant part of make.conf for completeness:

.if !defined(CC) || ${CC} == "cc"
CC=clang
.endif
.if !defined(CXX) || ${CXX} == "c++"
CXX=clang++
.endif
.if !defined(CPP) || ${CPP} == "cpp"
CPP=clang -E
.endif
NO_WERROR=
WERROR=
NO_FSCHG=
CPUTYPE?=corei7
CFLAGS= -O2 -pipe
COPTFLAGS= -O2 -pipe

Any thoughts? Is there some simple fix for this I'm missing?

Thanks,
Jason