Hi,
I'm doing some modifections to the avr backend to suit my needs.
I would like to add new constrainst for individual registers to use in
inline assembly blocks and i was wondering what is the correct way of
doing this?
Not on topic: You can have a look at GCC's "Specifying Registers for
Local Variables" feature:
http://gcc.gnu.org/onlinedocs/gcc/Local-Reg-Vars.html#Local-Reg-Vars
For example, this enables you to interface non-ABI assembler functions
with C code without patching the compiler.
Moreover, introducing individual register classes will result in a zoo
of constraints for 8-bit, 16-bit, 32-bit registers.
in gcc-4.5, i've added a new class for each register to reg_class,
REG_CLASS_NAMES and REG_CLASS_CONTENTS, made a need constrainst for
each register using its class and it worked as expected.
i tried to do the same in gcc-4.7 and i got:
internal compiler error: in find_costs_and_classes, at ira-costs.c:1704.
You will have to debug the compiler proper.
Notice that hooks like HARD_REGNO_MODE_OK put additional restrictions on
registers/mode combinations.
So i was wondering whether i did the wrong thing or just forgot to
update some target hook.
Thanks,
Ilya.
