This patch optimizes shuffle instruction - generates 2 instructions instead of 4.

Since this specific shuffle is widely used in many workloads we have ~10% performance on them.

shufflevector <8 x float> %A, <8 x float> %B, <8 x i32> <i32 0, i32 8, i32 2, i32 10, i32 4, i32 12, i32 6, i32 14>

vmovaps (%rdx), %ymm0
vshufps $8, %ymm0, %ymm0, %ymm0
vmovaps (%rcx), %ymm1
vshufps $8, %ymm0, %ymm1, %ymm1
vunpcklps       %ymm0, %ymm1, %ymm0

vmovaps (%rcx), %ymm0
vmovsldup       (%rdx), %ymm1
vblendps        $85, %ymm0, %ymm1, %ymm0

llvm-svn: 163134