ld and the H8/300

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ld and the H8/300

For the H8/300, ld can perform these global optimizations when you specify the ‘-relax’ command-line option.

relaxing address modes

ld finds all jsr and jmp instructions whose targets are within eight bits, and turns them into eight-bit program-counter relative bsr and bra instructions, respectively.

synthesizing instructions

ld finds all mov.b instructions which use the sixteen-bit absolute address form, but refer to the top page of memory, and changes them to use the eight-bit address form. (That is, the linker turns ‘mov.b @ aa:16’ into ‘mov.b @ aa:8’ whenever the address aa is in the top page of memory).

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