https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84826
--- Comment #4 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > So I looked into this. Turns out the actual issue is that USE_RETURN_INSN > (FALSE) changes its value and becomes false after pass ce3. > > According to what I can see, arm_r3_live_at_start_p() starts to return true > after ce3. Right and I think that we can live that. > My question is: > 1) Is there any easy way to avoid the false positives from > arm_r3_live_at_start_p() I don't think so. > 2) Why is r3 still live at IN of BB2 when there is no reaching definition of > it? I mean also there will never be any reaching definition at IN of BB2. Because r3 is an argument register so it has got an artifical def on entry: ;; entry block defs 0 [r0] 1 [r1] 2 [r2] 3 [r3] 12 [ip] 13 [sp] 14 [lr] IMO the issue is that arm_compute_static_chain_stack_bytes changes its value and this doesn't make sense since whether or not the static chain is pushed onto the stack is decided once for all at prologue time. So the fix is probably to cache the value of the function in the machine_function structure and return this cached value after prologue/epilogue generation (e.g. epilogue_completed == 1).
