In http://gcc.gnu.org/ml/gcc/2006-12/msg00328.html, you wrote:
>> On 06 Dec 2006 23:13:35 -0800, Ian Lance Taylor <[EMAIL PROTECTED]> wrote: >> If you can't afford to lose a register, then I think your only option >> is to pick some callee-saved register and have each branch instruction >> explicitly clobber it. Then it will be available for use in a long >> branch, and it will be available for use within a basic block. This >> is far from ideal, but I don't know a better way to handle it within >> gcc's current framework. > Can i get more clarity on this part. Is it implemented in any other backends? > When you say "pick some callee-saved register ", is it to pick them > randomly from an available set in CALL_USED_REGISTERS or a specific > register. The SH does register scavenging, and sharing of far branches. Look at config/sh/sh.c:split_branches . Also see PR 29336 for how this could be better integrated with machine-specific constant pool placement. However, because the SH has delayed branches, there is always a guaranteed way to find a register - one can be saved, and then be restored in the delay slot. An architecture without delay slots would have to have another fallback mechanism, e.g. inserting a register restore before the target - possibly with a short jump around it, duplicate instructions from the target till a register dies, or inserting a register restore and jump in the vincinity of the target.
