psubq (64bit - 64bit = 64bit):
movq mm7, mmc
psubd mmc, mms
movq mm6, mmc
psubd mm7, 0×80000000
psubd mm6, 0×80000000
pcmpgtd mm6, mm7
psllq mm6, 32
psubd mmc, mm6
psubq (64bit - 64bit = 64bit):
movq mm7, mmc
psubd mmc, mms
movq mm6, mmc
psubd mm7, 0×80000000
psubd mm6, 0×80000000
pcmpgtd mm6, mm7
psllq mm6, 32
psubd mmc, mm6