From: John M. <ato...@gm...> - 2010-11-04 00:20:07
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> - If ptrs were 8 bits we could have a reg class with r26, r28 and r30 for > st/ld and the compiler would be able to choose between this class what reg > to use. However we have to stick with reg pairs so we have to think how to > overcome this, if we dont use reg classes will we have to decide which pair > has to be used manually in each operation??. > Also notice that we should try to avoid using X to access struct members or > whatever because it doesnt support doing "X+<offs>" so we have to see how to > handle different addressing modes, favouring Y or Z in such cases etc. > The avr-gcc ABI uses the Y ptr for the stack frame so that would leave the Z ptr as the favored pointer. |