cad2074587
Converting something like iadd.i64 on a 32-bits architecture into a iadd_imm.i64 will result in the instruction being legalized back to an iadd.i64 later on, creating unnecessary churn. This commit implements avoid doing so, and changes the target ISA to a 64-bits platform for tests than ran into this, as well as making sure this won't happen on 32-bits platforms.