This patch implements lowerLoad and extends existing lowerStore for byte, short and floating-point types.
The patch also modifies PostLoweringLegalizer for conversion of mov to load or store.

R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/2301303003 .

Patch from Jaydeep Patil <jaydeep.patil@imgtec.com>.