cirrus75 <cirru...@uol.com.br> writes: > I could not understand exactly how to specify instruction size to gcc (so it > can really optimize the code size when -Os is used). > > I would like to inform gcc that if some registers are used for certain > operations, the instruction will be smaller. For example, an add which > destination register is register 4 has lowest size if compared to all "add" > forms. > > What is the easiest way to give this information to gcc ? I took a long look > at the internals documentation and other ports but I'm not sure.
You should add a "length" attribute to all your insns. However, the real way that gcc decides which insns to use is based on TARGET_RTX_COSTS. You can change what that returns based on the optimization mode. Ian
