toolchain from below:
http://autobuilder.yoctoproject.org/pub/nightly/20120919-2/toolchain/x86_64/poky-eglibc-x86_64-mips-toolchain-gmae-1.2+snapshot-20120919.sh

steps below:
1.install toolchain to "/opt/poky/1.2+snapshot".
2.run "source /opt/poky/1.2+snapshot/environment-setup-mips32-poky-linux".
3.run "${CC} -o test test.c -lm"
4.run "qemu-mips /opt/poky/1.2+snapshot/sysroots/mips32-poky-linux/lib/ld.so.1 --library-path /opt/poky/1.2+snapshot/sysroots/mips32-poky-linux/lib:/opt/poky/1.2+snapshot/sysroots/mips32-poky-linux/usr/lib ./test"

errors below:
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Segmentation fault (core dumped)

run "file ./test",output below:
./test: ELF 32-bit MSB executable, MIPS, MIPS32 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.16, with unknown capability 0x41000000 = 0xf676e75, with unknown capability 0x10000 = 0x70401, not stripped

test.c below:
#include <stdio.h>
#include <math.h>
double convert(long long l)
{
return (double)l;// or double(l)
}

int main(int argc, char * argv[])
{
long long l = 10;
double f;
f = convert(l);
printf("convert: %lld => %f\n", l, f);
f = 1234.67;
printf("floorf(%f) = %f\n", f, floorf(f));
return 0;
}


test env :
host :ubuntu 12.04 x86_64

git info:52850f0fc6f801298413ee779834b346ef7f48d6
git branch: poky/1.3_M5