Before this patch, we would emit a cmp or test with a memory operand only if both of the operands in the IR were loads. Now if either of them is a load and the other one is an immediate, we can use a memory operand if the load representation machine size is wide enough to represent the latter.

Review-Url: https://codereview.chromium.org/1948453002
Cr-Commit-Position: refs/heads/master@{#36009}