My environment:
Linux YYYXXX 3.2.0-55-generic-pae #85-Ubuntu SMP Wed Oct 2 14:03:15 UTC 2013 i686 i686 i386 GNU/Linux

MIPS toolchain:
mips-linux-gnu-gcc (Sourcery G++ Lite 4.3-51) 4.3.2

Affected valgrind versions: 3.9.0 and 3.8.1

Compilation always hang on this step:
18917 pts/15   R+    12:36 /opt/toolchains/mips-4.3/bin/../libexec/gcc/mips-linux-gnu/4.3.2/cc1 -quiet -I. -I.. -I.. -I../include -I../VEX/pub -iprefix /opt/toolchains/mips-4.3/bin/../lib/gcc/mips-linux-gnu/4.3.2/ -isysroot /opt/toolchains/mips-4.3/bin/../mips-linux-gnu/libc -MD drd_mips32_linux-drd_clientreq.d -MF .deps/drd_mips32_linux-drd_clientreq.Tpo -MP -MT drd_mips32_linux-drd_clientreq.o -DHAVE_CONFIG_H -DVGA_mips32=1 -DVGO_linux=1 -DVGP_mips32_linux=1 -DVGPV_mips32_linux_vanilla=1 drd_clientreq.c -quiet -dumpbase drd_clientreq.c -mips32 -mips32r2 -mhard-float -mllsc -mno-shared -mabicalls -auxbase-strip drd_mips32_linux-drd_clientreq.o -g -O2 -O2 -Wall -Wmissing-prototypes -Wshadow -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -Wno-format-zero-length -Wextra -Wformat-nonliteral -Wno-inline -Wno-unused-parameter -Wno-long-long -Wwrite-strings -fno-strict-aliasing -fno-builtin -fno-stack-protector --param inline-unit-growth=900 -o /tmp/ccBrFUT7.s

and temporary file always have zero size:
-rw------- 1 xxxx  yyy          0 Nov  5 13:38 ccBrFUT7.s

My steps of building:
./autogen.sh
./configure --host=mipsel-linux-gnu --prefix=/home/pub/valgrind CFLAGS="-mips32r2" CC=/opt/toolchains/mips-4.3/bin/mips-linux-gnu-gcc CXX=/opt/toolchains/mips-4.3/bin/mips-linux-gnu-c++
make -j6

Note: my toolchain doesn't support -mplt. 

Of course most likely it's toolchain fault, but may be some of compilation flags are missed for MIPS arch or some of them redundant and cause hang of compilation.