Re: [avr-gcc-list] Why is gcc promoting on an unsigned char?

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J.C. Wren wrote:

| 	It would still be nice if the register tracking was smart enough to
realize
| that the results are never being used on the high byte, and optimized
those
| out, though.

Speaking as someone who fell into this trap as well... :)

One could, I suppose, hack the avr md (machine description) file to
recognize this case and perform a special translation to do the Right
Thing. Then recompile gcc and it should work. The way to do it is
explained in the GCC manual, but it's quite difficult to go through.
What we need is a "Baby's First Book of GCC Machine Descriptions" or
something :)

- --Rob

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