[EMAIL PROTECTED] writes: > Here I've used a macro to keep track of the farthest place reached in the > code. As you can see, I've even tried to set it up in such a way that it > will use a register to access the value. However, I don't get that result, > as I guess that is optimized out. Instead each comparison uses the full > address of the array, creating two more words for the read and for the > write. I'd prefer a sequence to read something like: > > movel #main_line, %a0 /* only once, at the start of the function */ > moveq #(LINE-1), %d0 > cmpl %a0@, %d0 > blt skip > moveb #LINE, %d0 > movel %d0,%a0@ > skip: ... > > I haven't seen any options that encourage more use of indirect addressing. > Are there any that I have missed? If not, I assume I will need to work > with the machine description. I've downloaded the gcc internals book, but > it's a lot of material and it's hard to figure out where to start. Can > anybody point me in the right direction?
The first thing to try is to use TARGET_ADDRESS_COST to make the cost of register indirect smaller than the cost of an absolute address reference, at least when optimize_space is true. m68k.c doesn't seem to have a definition of TARGET_ADDRESS_COST, so you will have to add one. You should also take a look at TARGET_RTX_COSTS. Ian
