------- Additional Comments From roger at eyesopen dot com 2005-01-25 21:23 ------- I'm currently working on an updated and improved patch that should address some of this size regression. Failing that there are a number of middle-end improvements that can be made to address the code size increase. For example, GCC's middle-end considers any constant with an rtx_cost greater than COSTS_N_INSNS(1) to be expensive, and therefore worth keeping in a register for CSE and GCSE. Unfortunately, this plays badly with AVR, where the cost of a register-register copy is often greater than COSTS_N_INSNS(1)! The solution to which is to introduce a REG_REG_MOVE_COST(mode) target macro that can be used to report the cost of copying a pseudo and use this instead of COSTS_N_INSNS(1) where appropriate. This should even help non-AVR platforms, for example DImode typically requires two move instructions.
The change described above should avoid AVR keeping HImode integer constants in registers and then copying them when required (its as cheap to load an immediate constant as it is to copy registers, but the later increases register pressure, stack frame size, etc...) -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19597
