  The most computationally demanding part of Lattice QCD simulations is solving
quark propagators. Quark propagators are typically obtained with a linear
equation solver utilizing HPC machines. The CCS QCD Benchmark is a benchmark
program solving the Wilson-Clover quark propagator, and is developed at the
Center for Computational Sciences (CCS), University of Tsukuba. We optimized
the benchmark program for a \Intel \XeonPhi (Knights Corner, KNC) system named
"COMA (PACS-IX)" at CCS Tsukuba under the Intel Parallel Computing Center
program. A single precision BiCGStab solver with the overlapped Restricted
Additive Schwarz (RAS) preconditioner was implemented using SIMD intrinsics,
OpenMP and MPI in the offload mode. With the reverse-offloading technique, we
could reduce the communication and offloading overheads. We observed a
performance of $\sim 200$ GFlops sustained for the Wilson-Clover hopping matrix
multiplication on the lattice sizes larger than $24^3\times 32$ on a sinlge
card of the COMA system. A good weak scaling perofmace was observed on the
local lattice sizes larger than $24^3\times 32$.
