Previously, `asm.mov(m32, imm32)` panicked when `imm32 > 0x80000000`. It attempted to split imm32 into a register before doing the store, but then the register size didn't match the destination size. Instead of splitting, use the `MOV r/m32, imm32` form which works for all 32-bit values. Adjust asserts that assumed that all forms undergo sign extension, which is not true for this case. See: 54edc930f9f0a658da45cfcef46648d1b6f82467