On 07/11/2018 02:07 PM, Steve Ellcey wrote: > I have a reload/register allocation question and possible patch. While > working on the Aarch64 SIMD ABI[1] I ran into a problem where GCC was > saving and restoring registers that it did not need to. I tracked it > down to lra-constraints.c and its use of > targetm.hard_regno_call_part_clobbered on instructions that are not > calls. Specifically need_for_call_save_p would check this macro even > when the instruction in question (unknown to need_for_call_save_p) > was not a call instruction. > > This seems wrong to me and I was wondering if anyone more familiar > with the register allocator and reload could look at this patch and > tell me if it seems reasonable or not. It passed bootstrap and I > am running tests now. I am just wondering if there is any reason why > this target function would need to be called on non-call instructions > or if doing so is just an oversight/bug. > > Steve Ellcey > sell...@cavium.com > > > [1] https://gcc.gnu.org/ml/gcc/2018-07/msg00012.html > > > 2018-07-11 Steve Ellcey <sell...@cavium.com> > > * lra-constraints.c (need_for_call_save_p): Add insn argument > and only check targetm.hard_regno_call_part_clobbered on calls. > (need_for_split_p): Add insn argument, pass to need_for_call_save_p. > (split_reg): Pass insn to need_for_call_save_p. > (split_if_necessary): Pass curr_insn to need_for_split_p. > (inherit_in_ebb): Ditto. Various target have calls which are exposed as INSNs rather than as CALL_INSNs. So we need to check that hook on all insns.
You can probably see this in action with the TLS insns on aarch64. jeff
