Assume that LD would optimize LDI32 instructions by checking the upper
16 bits of the expression. If they are all zeros, then LD would
shorten the LDI32 instruction to a single LDI. In such case
will output DIFF relocations for diff expressions.
Assume that LD would not optimize LDI32 instructions. As a consequence, DIFF relocations will not be emitted.
Do not warn if a label name matches a register name. Usually assembler programmers will want this warning to be emitted. C compilers may want to turn this off.